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1041 lines
40 KiB
C
1041 lines
40 KiB
C
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#if 0 /* in case someone actually tries to compile this */
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/* example.c - an example of using libpng
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*
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* Maintained 2018 Cosmin Truta
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* Maintained 1998-2016 Glenn Randers-Pehrson
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* Maintained 1996-1997 Andreas Dilger
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* Written 1995-1996 Guy Eric Schalnat, Group 42, Inc.
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*
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* To the extent possible under law, the authors have waived
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* all copyright and related or neighboring rights to this file.
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* This work is published from: United States, Canada.
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*/
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/* This is an example of how to use libpng to read and write PNG files.
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* The file libpng-manual.txt is much more verbose then this. If you have
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* not read it, do so first. This was designed to be a starting point of an
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* implementation. This is not officially part of libpng, is hereby placed
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* in the public domain, and therefore does not require a copyright notice.
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*
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* This file does not currently compile, because it is missing certain
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* parts, like allocating memory to hold an image. You will have to
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* supply these parts to get it to compile. For an example of a minimal
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* working PNG reader/writer, see pngtest.c, included in this distribution;
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* see also the programs in the contrib directory.
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*/
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/* The simple, but restricted approach to reading a PNG file or data stream
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* requires just two function calls, as in the following complete program.
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* Writing a file needs just one function call, so long as the data has an
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* appropriate layout.
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*
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* The following code reads PNG image data from a file and writes it, in a
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* potentially new format, to a new file. While this code will compile, there
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* is minimal (insufficient) error checking. For a more realistic version,
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* see contrib/examples/pngtopng.c
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*/
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#include <stddef.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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#include <png.h>
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#include <zlib.h>
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int main(int argc, const char **argv)
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{
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if (argc == 3)
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{
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png_image image; /* The control structure used by libpng */
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/* Initialize the 'png_image' structure. */
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memset(&image, 0, (sizeof image));
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image.version = PNG_IMAGE_VERSION;
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/* The first argument is the file to read: */
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if (png_image_begin_read_from_file(&image, argv[1]) != 0)
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{
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png_bytep buffer;
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/* Set the format in which to read the PNG file; this code chooses a
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* simple sRGB format with a non-associated alpha channel, adequate to
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* store most images.
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*/
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image.format = PNG_FORMAT_RGBA;
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/* Now allocate enough memory to hold the image in this format; the
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* PNG_IMAGE_SIZE macro uses the information about the image (width,
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* height and format) stored in 'image'.
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*/
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buffer = malloc(PNG_IMAGE_SIZE(image));
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/* If enough memory was available, read the image in the desired
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* format, then write the result out to the new file. 'background' is
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* not necessary when reading the image, because the alpha channel is
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* preserved; if it were to be removed, for example if we requested
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* PNG_FORMAT_RGB, then either a solid background color would have to
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* be supplied, or the output buffer would have to be initialized to
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* the actual background of the image.
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*
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* The fourth argument to png_image_finish_read is the 'row_stride' -
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* this is the number of components allocated for the image in each
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* row. It has to be at least as big as the value returned by
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* PNG_IMAGE_ROW_STRIDE, but if you just allocate space for the
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* default, minimum size, using PNG_IMAGE_SIZE as above, you can pass
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* zero.
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*
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* The final argument is a pointer to a buffer for the colormap;
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* colormaps have exactly the same format as a row of image pixels
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* (so you choose what format to make the colormap by setting
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* image.format). A colormap is only returned if
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* PNG_FORMAT_FLAG_COLORMAP is also set in image.format, so in this
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* case NULL is passed as the final argument. If you do want to force
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* all images into an index/color-mapped format, then you can use:
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*
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* PNG_IMAGE_COLORMAP_SIZE(image)
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*
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* to find the maximum size of the colormap in bytes.
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*/
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if (buffer != NULL &&
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png_image_finish_read(&image, NULL/*background*/, buffer,
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0/*row_stride*/, NULL/*colormap*/) != 0)
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{
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/* Now write the image out to the second argument. In the write
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* call 'convert_to_8bit' allows 16-bit data to be squashed down to
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* 8 bits; this isn't necessary here because the original read was
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* to the 8-bit format.
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*/
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if (png_image_write_to_file(&image, argv[2], 0/*convert_to_8bit*/,
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buffer, 0/*row_stride*/, NULL/*colormap*/) != 0)
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{
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/* The image has been written successfully. */
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exit(0);
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}
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}
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else
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{
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/* Calling png_image_free is optional unless the simplified API was
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* not run to completion. In this case, if there wasn't enough
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* memory for 'buffer', we didn't complete the read, so we must
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* free the image:
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*/
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if (buffer == NULL)
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png_image_free(&image);
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else
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free(buffer);
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}
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/* Something went wrong reading or writing the image. libpng stores a
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* textual message in the 'png_image' structure:
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*/
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fprintf(stderr, "pngtopng: error: %s\n", image.message);
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exit(1);
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}
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fprintf(stderr, "pngtopng: usage: pngtopng input-file output-file\n");
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exit(2);
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}
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/* That's it ;-) Of course you probably want to do more with PNG files than
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* just converting them all to 32-bit RGBA PNG files; you can do that between
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* the call to png_image_finish_read and png_image_write_to_file. You can also
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* ask for the image data to be presented in a number of different formats.
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* You do this by simply changing the 'format' parameter set before allocating
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* the buffer.
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*
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* The format parameter consists of five flags that define various aspects of
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* the image. You can simply add these together to get the format, or you can
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* use one of the predefined macros from png.h (as above):
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*
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* PNG_FORMAT_FLAG_COLOR: if set, the image will have three color components
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* per pixel (red, green and blue); if not set, the image will just have one
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* luminance (grayscale) component.
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*
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* PNG_FORMAT_FLAG_ALPHA: if set, each pixel in the image will have an
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* additional alpha value; a linear value that describes the degree the
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* image pixel covers (overwrites) the contents of the existing pixel on the
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* display.
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*
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* PNG_FORMAT_FLAG_LINEAR: if set, the components of each pixel will be
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* returned as a series of 16-bit linear values; if not set, the components
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* will be returned as a series of 8-bit values encoded according to the
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* sRGB standard. The 8-bit format is the normal format for images intended
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* for direct display, because almost all display devices do the inverse of
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* the sRGB transformation to the data they receive. The 16-bit format is
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* more common for scientific data and image data that must be further
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* processed; because it is linear, simple math can be done on the component
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* values. Regardless of the setting of this flag, the alpha channel is
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* always linear, although it will be 8 bits or 16 bits wide as specified by
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* the flag.
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*
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* PNG_FORMAT_FLAG_BGR: if set, the components of a color pixel will be
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* returned in the order blue, then green, then red. If not set, the pixel
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* components are in the order red, then green, then blue.
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*
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* PNG_FORMAT_FLAG_AFIRST: if set, the alpha channel (if present) precedes the
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* color or grayscale components. If not set, the alpha channel follows the
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* components.
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*
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* You do not have to read directly from a file. You can read from memory or,
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* on systems that support it, from a <stdio.h> FILE*. This is controlled by
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* the particular png_image_read_from_ function you call at the start.
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* Likewise, on write, you can write to a FILE* if your system supports it.
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* Check the macro PNG_STDIO_SUPPORTED to see if stdio support has been
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* included in your libpng build.
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*
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* If you read 16-bit (PNG_FORMAT_FLAG_LINEAR) data, you may need to write it
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* in the 8-bit format for display. You do this by setting the convert_to_8bit
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* flag to 'true'.
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*
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* Don't repeatedly convert between the 8-bit and 16-bit forms. There is
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* significant data loss when 16-bit data is converted to the 8-bit encoding,
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* and the current libpng implementation of conversion to 16-bit is also
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* significantly lossy. The latter will be fixed in the future, but the former
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* is unavoidable - the 8-bit format just doesn't have enough resolution.
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*/
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/* If your program needs more information from the PNG data it reads, or if you
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* need to do more complex transformations, or minimize transformations, on the
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* data you read, then you must use one of the several lower level libpng
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* interfaces.
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*
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* All these interfaces require that you do your own error handling - your
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* program must be able to arrange for control to return to your own code, any
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* time libpng encounters a problem. There are several ways to do this, but
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* the standard way is to use the <setjmp.h> interface to establish a return
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* point within your own code. You must do this if you do not use the
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* simplified interface (above).
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*
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* The first step is to include the header files you need, including the libpng
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* header file. Include any standard headers and feature test macros your
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* program requires before including png.h:
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*/
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#include <png.h>
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/* The png_jmpbuf() macro, used in error handling, became available in
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* libpng version 1.0.6. If you want to be able to run your code with older
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* versions of libpng, you must define the macro yourself (but only if it
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* is not already defined by libpng!)
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*/
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#ifndef png_jmpbuf
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# define png_jmpbuf(png_ptr) ((png_ptr)->png_jmpbuf)
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#endif
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/* Check to see if a file is a PNG file using png_sig_cmp(). png_sig_cmp()
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* returns zero if the image is a PNG, and nonzero otherwise.
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*
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* The function check_if_png() shown here, but not used, returns nonzero (true)
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* if the file can be opened and is a PNG, and 0 (false) otherwise.
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*
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* If this call is successful, and you are going to keep the file open,
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* you should call png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK); once
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* you have created the png_ptr, so that libpng knows your application
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* has read that many bytes from the start of the file. Make sure you
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* don't call png_set_sig_bytes() with more than 8 bytes read or give it
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* an incorrect number of bytes read, or you will either have read too
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* many bytes (your fault), or you are telling libpng to read the wrong
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* number of magic bytes (also your fault).
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*
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* Many applications already read the first 2 or 4 bytes from the start
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* of the image to determine the file type, so it would be easiest just
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* to pass the bytes to png_sig_cmp(), or even skip that if you know
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* you have a PNG file, and call png_set_sig_bytes().
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*/
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#define PNG_BYTES_TO_CHECK 4
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int check_if_png(char *file_name, FILE **fp)
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{
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char buf[PNG_BYTES_TO_CHECK];
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/* Open the prospective PNG file. */
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if ((*fp = fopen(file_name, "rb")) == NULL)
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return 0;
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/* Read in some of the signature bytes. */
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if (fread(buf, 1, PNG_BYTES_TO_CHECK, *fp) != PNG_BYTES_TO_CHECK)
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return 0;
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/* Compare the first PNG_BYTES_TO_CHECK bytes of the signature.
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* Return nonzero (true) if they match.
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*/
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return(!png_sig_cmp(buf, 0, PNG_BYTES_TO_CHECK));
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}
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/* Read a PNG file. You may want to return an error code if the read
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* fails (depending upon the failure). There are two "prototypes" given
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* here - one where we are given the filename, and we need to open the
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* file, and the other where we are given an open file (possibly with
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* some or all of the magic bytes read - see comments above).
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*/
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#ifdef open_file /* prototype 1 */
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void read_png(char *file_name) /* We need to open the file */
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{
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png_structp png_ptr;
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png_infop info_ptr;
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int sig_read = 0;
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png_uint_32 width, height;
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int bit_depth, color_type, interlace_type;
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FILE *fp;
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if ((fp = fopen(file_name, "rb")) == NULL)
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return (ERROR);
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#else no_open_file /* prototype 2 */
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void read_png(FILE *fp, int sig_read) /* File is already open */
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{
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png_structp png_ptr;
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png_infop info_ptr;
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png_uint_32 width, height;
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int bit_depth, color_type, interlace_type;
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#endif no_open_file /* Only use one prototype! */
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/* Create and initialize the png_struct with the desired error handler
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* functions. If you want to use the default stderr and longjump method,
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* you can supply NULL for the last three parameters. We also supply the
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* the compiler header file version, so that we know if the application
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* was compiled with a compatible version of the library. REQUIRED.
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*/
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png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
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png_voidp user_error_ptr, user_error_fn, user_warning_fn);
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if (png_ptr == NULL)
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{
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fclose(fp);
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return (ERROR);
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}
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/* Allocate/initialize the memory for image information. REQUIRED. */
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info_ptr = png_create_info_struct(png_ptr);
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if (info_ptr == NULL)
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{
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fclose(fp);
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png_destroy_read_struct(&png_ptr, NULL, NULL);
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return (ERROR);
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}
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/* Set error handling if you are using the setjmp/longjmp method (this is
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* the normal method of doing things with libpng). REQUIRED unless you
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* set up your own error handlers in the png_create_read_struct() earlier.
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*/
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if (setjmp(png_jmpbuf(png_ptr)))
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{
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/* Free all of the memory associated with the png_ptr and info_ptr. */
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png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
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fclose(fp);
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/* If we get here, we had a problem reading the file. */
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return (ERROR);
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}
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/* One of the following I/O initialization methods is REQUIRED. */
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#ifdef streams /* PNG file I/O method 1 */
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/* Set up the input control if you are using standard C streams. */
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png_init_io(png_ptr, fp);
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#else no_streams /* PNG file I/O method 2 */
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/* If you are using replacement read functions, instead of calling
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* png_init_io(), you would call:
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*/
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png_set_read_fn(png_ptr, (void *)user_io_ptr, user_read_fn);
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/* where user_io_ptr is a structure you want available to the callbacks. */
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#endif no_streams /* Use only one I/O method! */
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/* If we have already read some of the signature */
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png_set_sig_bytes(png_ptr, sig_read);
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#ifdef hilevel
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/* If you have enough memory to read in the entire image at once,
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* and you need to specify only transforms that can be controlled
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* with one of the PNG_TRANSFORM_* bits (this presently excludes
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* quantizing, filling, setting background, and doing gamma
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* adjustment), then you can read the entire image (including
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* pixels) into the info structure with this call:
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*/
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png_read_png(png_ptr, info_ptr, png_transforms, NULL);
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#else
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/* OK, you're doing it the hard way, with the lower-level functions. */
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/* The call to png_read_info() gives us all of the information from the
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* PNG file before the first IDAT (image data chunk). REQUIRED.
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*/
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png_read_info(png_ptr, info_ptr);
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png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
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&interlace_type, NULL, NULL);
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/* Set up the data transformations you want. Note that these are all
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* optional. Only call them if you want/need them. Many of the
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* transformations only work on specific types of images, and many
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* are mutually exclusive.
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*/
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/* Tell libpng to strip 16 bits/color files down to 8 bits/color.
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* Use accurate scaling if it's available, otherwise just chop off the
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* low byte.
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*/
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#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
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png_set_scale_16(png_ptr);
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#else
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png_set_strip_16(png_ptr);
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#endif
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/* Strip alpha bytes from the input data without combining with the
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* background (not recommended).
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*/
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png_set_strip_alpha(png_ptr);
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/* Extract multiple pixels with bit depths of 1, 2 or 4 from a single
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* byte into separate bytes (useful for paletted and grayscale images).
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*/
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png_set_packing(png_ptr);
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/* Change the order of packed pixels to least significant bit first
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* (not useful if you are using png_set_packing).
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*/
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png_set_packswap(png_ptr);
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/* Expand paletted colors into true RGB triplets. */
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if (color_type == PNG_COLOR_TYPE_PALETTE)
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png_set_palette_to_rgb(png_ptr);
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/* Expand grayscale images to the full 8 bits from 1, 2 or 4 bits/pixel. */
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if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
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png_set_expand_gray_1_2_4_to_8(png_ptr);
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/* Expand paletted or RGB images with transparency to full alpha channels
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* so the data will be available as RGBA quartets.
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*/
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if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS) != 0)
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png_set_tRNS_to_alpha(png_ptr);
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|
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/* Set the background color to draw transparent and alpha images over.
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* It is possible to set the red, green and blue components directly
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* for paletted images, instead of supplying a palette index. Note that,
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* even if the PNG file supplies a background, you are not required to
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* use it - you should use the (solid) application background if it has one.
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*/
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png_color_16 my_background, *image_background;
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if (png_get_bKGD(png_ptr, info_ptr, &image_background) != 0)
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png_set_background(png_ptr, image_background,
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PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
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else
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png_set_background(png_ptr, &my_background,
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PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
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/* Some suggestions as to how to get a screen gamma value.
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*
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* Note that screen gamma is the display_exponent, which includes
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* the CRT_exponent and any correction for viewing conditions.
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*/
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if (/* We have a user-defined screen gamma value */)
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screen_gamma = user-defined screen_gamma;
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/* This is one way that applications share the same screen gamma value. */
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else if ((gamma_str = getenv("SCREEN_GAMMA")) != NULL)
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screen_gamma = atof(gamma_str);
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/* If we don't have another value */
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else
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{
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screen_gamma = PNG_DEFAULT_sRGB; /* A good guess for a PC monitor
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in a dimly lit room */
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screen_gamma = PNG_GAMMA_MAC_18 or 1.0; /* Good guesses for Mac
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systems */
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}
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/* Tell libpng to handle the gamma conversion for you. The final call
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|
* is a good guess for PC generated images, but it should be configurable
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* by the user at run time. Gamma correction support in your application
|
|
* is strongly recommended.
|
|
*/
|
|
|
|
int intent;
|
|
|
|
if (png_get_sRGB(png_ptr, info_ptr, &intent) != 0)
|
|
png_set_gamma(png_ptr, screen_gamma, PNG_DEFAULT_sRGB);
|
|
else
|
|
{
|
|
double image_gamma;
|
|
if (png_get_gAMA(png_ptr, info_ptr, &image_gamma) != 0)
|
|
png_set_gamma(png_ptr, screen_gamma, image_gamma);
|
|
else
|
|
png_set_gamma(png_ptr, screen_gamma, 0.45455);
|
|
}
|
|
|
|
#ifdef PNG_READ_QUANTIZE_SUPPORTED
|
|
/* Quantize RGB files down to 8-bit palette, or reduce palettes
|
|
* to the number of colors available on your screen.
|
|
*/
|
|
if ((color_type & PNG_COLOR_MASK_COLOR) != 0)
|
|
{
|
|
int num_palette;
|
|
png_colorp palette;
|
|
|
|
/* This reduces the image to the application-supplied palette. */
|
|
if (/* We have our own palette */)
|
|
{
|
|
/* An array of colors to which the image should be quantized. */
|
|
png_color std_color_cube[MAX_SCREEN_COLORS];
|
|
png_set_quantize(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
|
|
MAX_SCREEN_COLORS, NULL, 0);
|
|
}
|
|
/* This reduces the image to the palette supplied in the file. */
|
|
else if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette) != 0)
|
|
{
|
|
png_uint_16p histogram = NULL;
|
|
png_get_hIST(png_ptr, info_ptr, &histogram);
|
|
png_set_quantize(png_ptr, palette, num_palette,
|
|
max_screen_colors, histogram, 0);
|
|
}
|
|
}
|
|
#endif /* READ_QUANTIZE */
|
|
|
|
/* Invert monochrome files to have 0 as white and 1 as black. */
|
|
png_set_invert_mono(png_ptr);
|
|
|
|
/* If you want to shift the pixel values from the range [0,255] or
|
|
* [0,65535] to the original [0,7] or [0,31], or whatever range the
|
|
* colors were originally in:
|
|
*/
|
|
if (png_get_valid(png_ptr, info_ptr, PNG_INFO_sBIT) != 0)
|
|
{
|
|
png_color_8p sig_bit_p;
|
|
png_get_sBIT(png_ptr, info_ptr, &sig_bit_p);
|
|
png_set_shift(png_ptr, sig_bit_p);
|
|
}
|
|
|
|
/* Flip the RGB pixels to BGR (or RGBA to BGRA). */
|
|
if ((color_type & PNG_COLOR_MASK_COLOR) != 0)
|
|
png_set_bgr(png_ptr);
|
|
|
|
/* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR). */
|
|
png_set_swap_alpha(png_ptr);
|
|
|
|
/* Swap bytes of 16-bit files to least significant byte first. */
|
|
png_set_swap(png_ptr);
|
|
|
|
/* Add filler (or alpha) byte (before/after each RGB triplet). */
|
|
png_set_filler(png_ptr, 0xffff, PNG_FILLER_AFTER);
|
|
|
|
#ifdef PNG_READ_INTERLACING_SUPPORTED
|
|
/* Turn on interlace handling. REQUIRED if you are not using
|
|
* png_read_image(). To see how to handle interlacing passes,
|
|
* see the png_read_row() method below:
|
|
*/
|
|
number_passes = png_set_interlace_handling(png_ptr);
|
|
#else /* !READ_INTERLACING */
|
|
number_passes = 1;
|
|
#endif /* READ_INTERLACING */
|
|
|
|
/* Optional call to gamma correct and add the background to the palette
|
|
* and update info structure. REQUIRED if you are expecting libpng to
|
|
* update the palette for you (i.e. you selected such a transform above).
|
|
*/
|
|
png_read_update_info(png_ptr, info_ptr);
|
|
|
|
/* Allocate the memory to hold the image using the fields of info_ptr. */
|
|
png_bytep row_pointers[height];
|
|
for (row = 0; row < height; row++)
|
|
row_pointers[row] = NULL; /* Clear the pointer array */
|
|
for (row = 0; row < height; row++)
|
|
row_pointers[row] = png_malloc(png_ptr, png_get_rowbytes(png_ptr,
|
|
info_ptr));
|
|
|
|
/* Now it's time to read the image. One of these methods is REQUIRED. */
|
|
#ifdef entire /* Read the entire image in one go */
|
|
png_read_image(png_ptr, row_pointers);
|
|
|
|
#else no_entire /* Read the image one or more scanlines at a time */
|
|
/* The other way to read images - deal with interlacing: */
|
|
for (pass = 0; pass < number_passes; pass++)
|
|
{
|
|
#ifdef single /* Read the image a single row at a time */
|
|
for (y = 0; y < height; y++)
|
|
png_read_rows(png_ptr, &row_pointers[y], NULL, 1);
|
|
|
|
#else no_single /* Read the image several rows at a time */
|
|
for (y = 0; y < height; y += number_of_rows)
|
|
{
|
|
#ifdef sparkle /* Read the image using the "sparkle" effect. */
|
|
png_read_rows(png_ptr, &row_pointers[y], NULL,
|
|
number_of_rows);
|
|
#else no_sparkle /* Read the image using the "rectangle" effect */
|
|
png_read_rows(png_ptr, NULL, &row_pointers[y],
|
|
number_of_rows);
|
|
#endif no_sparkle /* Use only one of these two methods */
|
|
}
|
|
|
|
/* If you want to display the image after every pass, do so here. */
|
|
#endif no_single /* Use only one of these two methods */
|
|
}
|
|
#endif no_entire /* Use only one of these two methods */
|
|
|
|
/* Read rest of file, and get additional chunks in info_ptr. REQUIRED. */
|
|
png_read_end(png_ptr, info_ptr);
|
|
#endif hilevel
|
|
|
|
/* At this point you have read the entire image. */
|
|
|
|
/* Clean up after the read, and free any memory allocated. REQUIRED. */
|
|
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
|
|
|
|
/* Close the file. */
|
|
fclose(fp);
|
|
|
|
/* That's it! */
|
|
return (OK);
|
|
}
|
|
|
|
/* Progressively read a file */
|
|
|
|
int
|
|
initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr)
|
|
{
|
|
/* Create and initialize the png_struct with the desired error handler
|
|
* functions. If you want to use the default stderr and longjump method,
|
|
* you can supply NULL for the last three parameters. We also check that
|
|
* the library version is compatible, in case we are using dynamically
|
|
* linked libraries.
|
|
*/
|
|
*png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
|
|
png_voidp user_error_ptr, user_error_fn, user_warning_fn);
|
|
if (*png_ptr == NULL)
|
|
{
|
|
*info_ptr = NULL;
|
|
return (ERROR);
|
|
}
|
|
*info_ptr = png_create_info_struct(png_ptr);
|
|
if (*info_ptr == NULL)
|
|
{
|
|
png_destroy_read_struct(png_ptr, info_ptr, NULL);
|
|
return (ERROR);
|
|
}
|
|
if (setjmp(png_jmpbuf((*png_ptr))))
|
|
{
|
|
png_destroy_read_struct(png_ptr, info_ptr, NULL);
|
|
return (ERROR);
|
|
}
|
|
|
|
/* You will need to provide all three function callbacks,
|
|
* even if you aren't using all of them.
|
|
* If you aren't using all functions, you can specify NULL
|
|
* parameters. Even when all three functions are NULL,
|
|
* you need to call png_set_progressive_read_fn().
|
|
* These functions shouldn't be dependent on global or
|
|
* static variables if you are decoding several images
|
|
* simultaneously. You should store stream specific data
|
|
* in a separate struct, given as the second parameter,
|
|
* and retrieve the pointer from inside the callbacks using
|
|
* the function png_get_progressive_ptr(png_ptr).
|
|
*/
|
|
png_set_progressive_read_fn(*png_ptr, (void *)stream_data,
|
|
info_callback, row_callback, end_callback);
|
|
return (OK);
|
|
}
|
|
|
|
int
|
|
process_data(png_structp *png_ptr, png_infop *info_ptr,
|
|
png_bytep buffer, png_uint_32 length)
|
|
{
|
|
if (setjmp(png_jmpbuf((*png_ptr))))
|
|
{
|
|
/* Free the png_ptr and info_ptr memory on error. */
|
|
png_destroy_read_struct(png_ptr, info_ptr, NULL);
|
|
return (ERROR);
|
|
}
|
|
|
|
/* Give chunks of data as they arrive from the data stream
|
|
* (in order, of course).
|
|
* On segmented machines, don't give it any more than 64K.
|
|
* The library seems to run fine with sizes of 4K, although
|
|
* you can give it much less if necessary. (I assume you can
|
|
* give it chunks of 1 byte, but I haven't tried with less
|
|
* than 256 bytes yet.) When this function returns, you may
|
|
* want to display any rows that were generated in the row
|
|
* callback, if you aren't already displaying them there.
|
|
*/
|
|
png_process_data(*png_ptr, *info_ptr, buffer, length);
|
|
return (OK);
|
|
}
|
|
|
|
info_callback(png_structp png_ptr, png_infop info)
|
|
{
|
|
/* Do any setup here, including setting any of the transformations
|
|
* mentioned in the Reading PNG files section. For now, you _must_
|
|
* call either png_start_read_image() or png_read_update_info()
|
|
* after all the transformations are set (even if you don't set
|
|
* any). You may start getting rows before png_process_data()
|
|
* returns, so this is your last chance to prepare for that.
|
|
*/
|
|
}
|
|
|
|
row_callback(png_structp png_ptr, png_bytep new_row,
|
|
png_uint_32 row_num, int pass)
|
|
{
|
|
/* This function is called for every row in the image. If the
|
|
* image is interlaced, and you turned on the interlace handler,
|
|
* this function will be called for every row in every pass.
|
|
*
|
|
* In this function you will receive a pointer to new row data from
|
|
* libpng called new_row that is to replace a corresponding row (of
|
|
* the same data format) in a buffer allocated by your application.
|
|
*
|
|
* The new row data pointer "new_row" may be NULL, indicating there is
|
|
* no new data to be replaced (in cases of interlace loading).
|
|
*
|
|
* If new_row is not NULL, then you need to call
|
|
* png_progressive_combine_row(), to replace the corresponding row as
|
|
* shown below:
|
|
*/
|
|
|
|
/* Get pointer to corresponding row in our PNG read buffer. */
|
|
png_bytep old_row = ((png_bytep *)our_data)[row_num];
|
|
|
|
#ifdef PNG_READ_INTERLACING_SUPPORTED
|
|
/* If both rows are allocated, then copy the new row
|
|
* data to the corresponding row data.
|
|
*/
|
|
if (old_row != NULL && new_row != NULL)
|
|
png_progressive_combine_row(png_ptr, old_row, new_row);
|
|
|
|
/* The rows and passes are called in order, so you don't really
|
|
* need the row_num and pass, but I'm supplying them because it
|
|
* may make your life easier.
|
|
*
|
|
* For the non-NULL rows of interlaced images, you must call
|
|
* png_progressive_combine_row() passing in the new row and the
|
|
* old row, as demonstrated above. You can call this function for
|
|
* NULL rows (it will just return) and for non-interlaced images
|
|
* (it just does the memcpy for you) if it will make the code
|
|
* easier. Thus, you can just do this for all cases:
|
|
*/
|
|
png_progressive_combine_row(png_ptr, old_row, new_row);
|
|
|
|
/* where old_row is what was displayed for previous rows. Note
|
|
* that the first pass (pass == 0 really) will completely cover
|
|
* the old row, so the rows do not have to be initialized. After
|
|
* the first pass (and only for interlaced images), you will have
|
|
* to pass the current row as new_row, and the function will combine
|
|
* the old row and the new row.
|
|
*/
|
|
#endif /* READ_INTERLACING */
|
|
}
|
|
|
|
end_callback(png_structp png_ptr, png_infop info)
|
|
{
|
|
/* This function is called when the whole image has been read,
|
|
* including any chunks after the image (up to and including
|
|
* the IEND). You will usually have the same info chunk as you
|
|
* had in the header, although some data may have been added
|
|
* to the comments and time fields.
|
|
*
|
|
* Most people won't do much here, perhaps setting a flag that
|
|
* marks the image as finished.
|
|
*/
|
|
}
|
|
|
|
/* Write a png file */
|
|
void write_png(char *file_name /* , ... other image information ... */)
|
|
{
|
|
FILE *fp;
|
|
png_structp png_ptr;
|
|
png_infop info_ptr;
|
|
png_colorp palette;
|
|
|
|
/* Open the file */
|
|
fp = fopen(file_name, "wb");
|
|
if (fp == NULL)
|
|
return (ERROR);
|
|
|
|
/* Create and initialize the png_struct with the desired error handler
|
|
* functions. If you want to use the default stderr and longjump method,
|
|
* you can supply NULL for the last three parameters. We also check that
|
|
* the library version is compatible with the one used at compile time,
|
|
* in case we are using dynamically linked libraries. REQUIRED.
|
|
*/
|
|
png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
|
|
png_voidp user_error_ptr, user_error_fn, user_warning_fn);
|
|
if (png_ptr == NULL)
|
|
{
|
|
fclose(fp);
|
|
return (ERROR);
|
|
}
|
|
|
|
/* Allocate/initialize the image information data. REQUIRED. */
|
|
info_ptr = png_create_info_struct(png_ptr);
|
|
if (info_ptr == NULL)
|
|
{
|
|
fclose(fp);
|
|
png_destroy_write_struct(&png_ptr, NULL);
|
|
return (ERROR);
|
|
}
|
|
|
|
/* Set up error handling. REQUIRED if you aren't supplying your own
|
|
* error handling functions in the png_create_write_struct() call.
|
|
*/
|
|
if (setjmp(png_jmpbuf(png_ptr)))
|
|
{
|
|
/* If we get here, we had a problem writing the file. */
|
|
fclose(fp);
|
|
png_destroy_write_struct(&png_ptr, &info_ptr);
|
|
return (ERROR);
|
|
}
|
|
|
|
/* One of the following I/O initialization functions is REQUIRED. */
|
|
|
|
#ifdef streams /* I/O initialization method 1 */
|
|
/* Set up the output control if you are using standard C streams. */
|
|
png_init_io(png_ptr, fp);
|
|
|
|
#else no_streams /* I/O initialization method 2 */
|
|
/* If you are using replacement write functions, instead of calling
|
|
* png_init_io(), you would call:
|
|
*/
|
|
png_set_write_fn(png_ptr, (void *)user_io_ptr, user_write_fn,
|
|
user_IO_flush_function);
|
|
/* where user_io_ptr is a structure you want available to the callbacks. */
|
|
#endif no_streams /* Only use one initialization method */
|
|
|
|
#ifdef hilevel
|
|
/* This is the easy way. Use it if you already have all the
|
|
* image info living in the structure. You could "|" many
|
|
* PNG_TRANSFORM flags into the png_transforms integer here.
|
|
*/
|
|
png_write_png(png_ptr, info_ptr, png_transforms, NULL);
|
|
|
|
#else
|
|
/* This is the hard way. */
|
|
|
|
/* Set the image information here. Width and height are up to 2^31,
|
|
* bit_depth is one of 1, 2, 4, 8 or 16, but valid values also depend on
|
|
* the color_type selected. color_type is one of PNG_COLOR_TYPE_GRAY,
|
|
* PNG_COLOR_TYPE_GRAY_ALPHA, PNG_COLOR_TYPE_PALETTE, PNG_COLOR_TYPE_RGB,
|
|
* or PNG_COLOR_TYPE_RGB_ALPHA. interlace is either PNG_INTERLACE_NONE or
|
|
* PNG_INTERLACE_ADAM7, and the compression_type and filter_type MUST
|
|
* currently be PNG_COMPRESSION_TYPE_BASE and PNG_FILTER_TYPE_BASE.
|
|
* REQUIRED.
|
|
*/
|
|
png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth,
|
|
PNG_COLOR_TYPE_???, PNG_INTERLACE_????,
|
|
PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
|
|
|
|
/* Set the palette if there is one. REQUIRED for indexed-color images. */
|
|
palette = (png_colorp)png_malloc(png_ptr,
|
|
PNG_MAX_PALETTE_LENGTH * (sizeof (png_color)));
|
|
/* ... Set palette colors ... */
|
|
png_set_PLTE(png_ptr, info_ptr, palette, PNG_MAX_PALETTE_LENGTH);
|
|
/* You must not free palette here, because png_set_PLTE only makes a link
|
|
* to the palette that you allocated. Wait until you are about to destroy
|
|
* the png structure.
|
|
*/
|
|
|
|
/* Optional significant bit (sBIT) chunk. */
|
|
png_color_8 sig_bit;
|
|
|
|
/* If we are dealing with a grayscale image then */
|
|
sig_bit.gray = true_bit_depth;
|
|
|
|
/* Otherwise, if we are dealing with a color image then */
|
|
sig_bit.red = true_red_bit_depth;
|
|
sig_bit.green = true_green_bit_depth;
|
|
sig_bit.blue = true_blue_bit_depth;
|
|
|
|
/* If the image has an alpha channel then */
|
|
sig_bit.alpha = true_alpha_bit_depth;
|
|
|
|
png_set_sBIT(png_ptr, info_ptr, &sig_bit);
|
|
|
|
/* Optional gamma chunk is strongly suggested if you have any guess
|
|
* as to the correct gamma of the image.
|
|
*/
|
|
png_set_gAMA(png_ptr, info_ptr, gamma);
|
|
|
|
/* Optionally write comments into the image. */
|
|
{
|
|
png_text text_ptr[3];
|
|
|
|
char key0[] = "Title";
|
|
char text0[] = "Mona Lisa";
|
|
text_ptr[0].key = key0;
|
|
text_ptr[0].text = text0;
|
|
text_ptr[0].compression = PNG_TEXT_COMPRESSION_NONE;
|
|
text_ptr[0].itxt_length = 0;
|
|
text_ptr[0].lang = NULL;
|
|
text_ptr[0].lang_key = NULL;
|
|
|
|
char key1[] = "Author";
|
|
char text1[] = "Leonardo DaVinci";
|
|
text_ptr[1].key = key1;
|
|
text_ptr[1].text = text1;
|
|
text_ptr[1].compression = PNG_TEXT_COMPRESSION_NONE;
|
|
text_ptr[1].itxt_length = 0;
|
|
text_ptr[1].lang = NULL;
|
|
text_ptr[1].lang_key = NULL;
|
|
|
|
char key2[] = "Description";
|
|
char text2[] = "<long text>";
|
|
text_ptr[2].key = key2;
|
|
text_ptr[2].text = text2;
|
|
text_ptr[2].compression = PNG_TEXT_COMPRESSION_zTXt;
|
|
text_ptr[2].itxt_length = 0;
|
|
text_ptr[2].lang = NULL;
|
|
text_ptr[2].lang_key = NULL;
|
|
|
|
png_set_text(write_ptr, write_info_ptr, text_ptr, 3);
|
|
}
|
|
|
|
/* Other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs. */
|
|
|
|
/* Note that if sRGB is present, the gAMA and cHRM chunks must be ignored
|
|
* on read and, if your application chooses to write them, they must
|
|
* be written in accordance with the sRGB profile.
|
|
*/
|
|
|
|
/* Write the file header information. REQUIRED. */
|
|
png_write_info(png_ptr, info_ptr);
|
|
|
|
/* If you want, you can write the info in two steps, in case you need to
|
|
* write your private chunk ahead of PLTE:
|
|
*
|
|
* png_write_info_before_PLTE(write_ptr, write_info_ptr);
|
|
* write_my_chunk();
|
|
* png_write_info(png_ptr, info_ptr);
|
|
*
|
|
* However, given the level of known- and unknown-chunk support in 1.2.0
|
|
* and up, this should no longer be necessary.
|
|
*/
|
|
|
|
/* Once we write out the header, the compression type on the text
|
|
* chunk gets changed to PNG_TEXT_COMPRESSION_NONE_WR or
|
|
* PNG_TEXT_COMPRESSION_zTXt_WR, so it doesn't get written out again
|
|
* at the end.
|
|
*/
|
|
|
|
/* Set up the transformations you want. Note that these are
|
|
* all optional. Only call them if you want them.
|
|
*/
|
|
|
|
/* Invert monochrome pixels. */
|
|
png_set_invert_mono(png_ptr);
|
|
|
|
/* Shift the pixels up to a legal bit depth and fill in
|
|
* as appropriate to correctly scale the image.
|
|
*/
|
|
png_set_shift(png_ptr, &sig_bit);
|
|
|
|
/* Pack pixels into bytes. */
|
|
png_set_packing(png_ptr);
|
|
|
|
/* Swap location of alpha bytes from ARGB to RGBA. */
|
|
png_set_swap_alpha(png_ptr);
|
|
|
|
/* Get rid of filler (OR ALPHA) bytes, pack XRGB/RGBX/ARGB/RGBA into
|
|
* RGB (4 channels -> 3 channels). The second parameter is not used.
|
|
*/
|
|
png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
|
|
|
|
/* Flip BGR pixels to RGB. */
|
|
png_set_bgr(png_ptr);
|
|
|
|
/* Swap bytes of 16-bit files to most significant byte first. */
|
|
png_set_swap(png_ptr);
|
|
|
|
/* Swap bits of 1-bit, 2-bit, 4-bit packed pixel formats. */
|
|
png_set_packswap(png_ptr);
|
|
|
|
/* Turn on interlace handling if you are not using png_write_image(). */
|
|
if (interlacing != 0)
|
|
number_passes = png_set_interlace_handling(png_ptr);
|
|
else
|
|
number_passes = 1;
|
|
|
|
/* The easiest way to write the image (you may have a different memory
|
|
* layout, however, so choose what fits your needs best). You need to
|
|
* use the first method if you aren't handling interlacing yourself.
|
|
*/
|
|
png_uint_32 k, height, width;
|
|
|
|
/* In this example, "image" is a one-dimensional array of bytes. */
|
|
|
|
/* Guard against integer overflow. */
|
|
if (height > PNG_SIZE_MAX / (width * bytes_per_pixel))
|
|
png_error(png_ptr, "Image data buffer would be too large");
|
|
|
|
png_byte image[height * width * bytes_per_pixel];
|
|
png_bytep row_pointers[height];
|
|
|
|
if (height > PNG_UINT_32_MAX / (sizeof (png_bytep)))
|
|
png_error(png_ptr, "Image is too tall to process in memory");
|
|
|
|
/* Set up pointers into your "image" byte array. */
|
|
for (k = 0; k < height; k++)
|
|
row_pointers[k] = image + k * width * bytes_per_pixel;
|
|
|
|
/* One of the following output methods is REQUIRED. */
|
|
|
|
#ifdef entire /* Write out the entire image data in one call */
|
|
png_write_image(png_ptr, row_pointers);
|
|
|
|
/* The other way to write the image - deal with interlacing. */
|
|
|
|
#else no_entire /* Write out the image data by one or more scanlines */
|
|
|
|
/* The number of passes is either 1 for non-interlaced images,
|
|
* or 7 for interlaced images.
|
|
*/
|
|
for (pass = 0; pass < number_passes; pass++)
|
|
{
|
|
/* Write a few rows at a time. */
|
|
png_write_rows(png_ptr, &row_pointers[first_row], number_of_rows);
|
|
|
|
/* If you are only writing one row at a time, this works. */
|
|
for (y = 0; y < height; y++)
|
|
png_write_rows(png_ptr, &row_pointers[y], 1);
|
|
}
|
|
#endif no_entire /* Use only one output method */
|
|
|
|
/* You can write optional chunks like tEXt, zTXt, and tIME at the end
|
|
* as well. Shouldn't be necessary in 1.2.0 and up, as all the public
|
|
* chunks are supported, and you can use png_set_unknown_chunks() to
|
|
* register unknown chunks into the info structure to be written out.
|
|
*/
|
|
|
|
/* It is REQUIRED to call this to finish writing the rest of the file. */
|
|
png_write_end(png_ptr, info_ptr);
|
|
#endif hilevel
|
|
|
|
/* If you png_malloced a palette, free it here.
|
|
* (Don't free info_ptr->palette, as shown in versions 1.0.5m and earlier of
|
|
* this example; if libpng mallocs info_ptr->palette, libpng will free it).
|
|
* If you allocated it with malloc() instead of png_malloc(), use free()
|
|
* instead of png_free().
|
|
*/
|
|
png_free(png_ptr, palette);
|
|
palette = NULL;
|
|
|
|
/* Similarly, if you png_malloced any data that you passed in with
|
|
* png_set_something(), such as a hist or trans array, free it here,
|
|
* when you can be sure that libpng is through with it.
|
|
*/
|
|
png_free(png_ptr, trans);
|
|
trans = NULL;
|
|
|
|
/* Whenever you use png_free(), it is a good idea to set the pointer to
|
|
* NULL in case your application inadvertently tries to png_free() it
|
|
* again. When png_free() sees a NULL it returns without action, avoiding
|
|
* the double-free problem.
|
|
*/
|
|
|
|
/* Clean up after the write, and free any allocated memory. */
|
|
png_destroy_write_struct(&png_ptr, &info_ptr);
|
|
|
|
/* Close the file. */
|
|
fclose(fp);
|
|
|
|
/* That's it! */
|
|
return (OK);
|
|
}
|
|
|
|
#endif /* if 0 */
|