mm7: lib/libpng/example.c comparison

comparison lib/libpng/example.c @ 2305:a5e8eecac226

Merge

author	Grumpy7
date	Sun, 16 Mar 2014 21:04:49 +0100
parents	5e2e171c6911
children

comparison

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-:e76b56512abd
+:a5e8eecac226
+#if 0 /* in case someone actually tries to compile this */
+/* example.c - an example of using libpng
+* Last changed in libpng 1.6.3 [July 18, 2013]
+* Maintained 1998-2013 Glenn Randers-Pehrson
+* Maintained 1996, 1997 Andreas Dilger)
+* Written 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
+* To the extent possible under law, the authors have waived
+* all copyright and related or neighboring rights to this file.
+* This work is published from: United States.
+*/
+/* This is an example of how to use libpng to read and write PNG files.
+* The file libpng-manual.txt is much more verbose then this.  If you have not
+* read it, do so first.  This was designed to be a starting point of an
+* implementation.  This is not officially part of libpng, is hereby placed
+* in the public domain, and therefore does not require a copyright notice.
+*
+* This file does not currently compile, because it is missing certain
+* parts, like allocating memory to hold an image.  You will have to
+* supply these parts to get it to compile.  For an example of a minimal
+* working PNG reader/writer, see pngtest.c, included in this distribution;
+* see also the programs in the contrib directory.
+*/
+/* The simple, but restricted, approach to reading a PNG file or data stream
+* just requires two function calls, as in the following complete program.
+* Writing a file just needs one function call, so long as the data has an
+* appropriate layout.
+*
+* The following code reads PNG image data from a file and writes it, in a
+* potentially new format, to a new file.  While this code will compile there is
+* minimal (insufficient) error checking; for a more realistic version look at
+* contrib/examples/pngtopng.c
+*/
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <png.h>
+#include <zlib.h>
+int main(int argc, const char **argv)
+{
+if (argc == 3)
+{
+png_image image; /* The control structure used by libpng */
+/* Initialize the 'png_image' structure. */
+memset(&image, 0, (sizeof image));
+image.version = PNG_IMAGE_VERSION;
+/* The first argument is the file to read: */
+if (png_image_begin_read_from_file(&image, argv[1]))
+{
+png_bytep buffer;
+/* Set the format in which to read the PNG file; this code chooses a
+* simple sRGB format with a non-associated alpha channel, adequate to
+* store most images.
+*/
+image.format = PNG_FORMAT_RGBA;
+/* Now allocate enough memory to hold the image in this format; the
+* PNG_IMAGE_SIZE macro uses the information about the image (width,
+* height and format) stored in 'image'.
+*/
+buffer = malloc(PNG_IMAGE_SIZE(image));
+/* If enough memory was available read the image in the desired format
+* then write the result out to the new file.  'background' is not
+* necessary when reading the image because the alpha channel is
+* preserved; if it were to be removed, for example if we requested
+* PNG_FORMAT_RGB, then either a solid background color would have to
+* be supplied or the output buffer would have to be initialized to the
+* actual background of the image.
+*
+* The fourth argument to png_image_finish_read is the 'row_stride' -
+* this is the number of components allocated for the image in each
+* row.  It has to be at least as big as the value returned by
+* PNG_IMAGE_ROW_STRIDE, but if you just allocate space for the
+* default, minimum, size using PNG_IMAGE_SIZE as above you can pass
+* zero.
+*
+* The final argument is a pointer to a buffer for the colormap;
+* colormaps have exactly the same format as a row of image pixels (so
+* you choose what format to make the colormap by setting
+* image.format).  A colormap is only returned if
+* PNG_FORMAT_FLAG_COLORMAP is also set in image.format, so in this
+* case NULL is passed as the final argument.  If you do want to force
+* all images into an index/color-mapped format then you can use:
+*
+*    PNG_IMAGE_COLORMAP_SIZE(image)
+*
+* to find the maximum size of the colormap in bytes.
+*/
+if (buffer != NULL &&
+png_image_finish_read(&image, NULL/*background*/, buffer,
+0/*row_stride*/, NULL/*colormap*/))
+{
+/* Now write the image out to the second argument.  In the write
+* call 'convert_to_8bit' allows 16-bit data to be squashed down to
+* 8 bits; this isn't necessary here because the original read was
+* to the 8-bit format.
+*/
+if (png_image_write_to_file(&image, argv[2], 0/*convert_to_8bit*/,
+buffer, 0/*row_stride*/, NULL/*colormap*/))
+{
+/* The image has been written successfully. */
+exit(0);
+}
+}
+else
+{
+/* Calling png_free_image is optional unless the simplified API was
+* not run to completion.  In this case if there wasn't enough
+* memory for 'buffer' we didn't complete the read, so we must free
+* the image:
+*/
+if (buffer == NULL)
+png_free_image(&image);
+else
+free(buffer);
+}
+/* Something went wrong reading or writing the image.  libpng stores a
+* textual message in the 'png_image' structure:
+*/
+fprintf(stderr, "pngtopng: error: %s\n", image.message);
+exit (1);
+}
+fprintf(stderr, "pngtopng: usage: pngtopng input-file output-file\n");
+exit(1);
+}
+/* That's it ;-)  Of course you probably want to do more with PNG files than
+* just converting them all to 32-bit RGBA PNG files; you can do that between
+* the call to png_image_finish_read and png_image_write_to_file.  You can also
+* ask for the image data to be presented in a number of different formats.  You
+* do this by simply changing the 'format' parameter set before allocating the
+* buffer.
+*
+* The format parameter consists of five flags that define various aspects of
+* the image, you can simply add these together to get the format or you can use
+* one of the predefined macros from png.h (as above):
+*
+* PNG_FORMAT_FLAG_COLOR: if set the image will have three color components per
+*    pixel (red, green and blue), if not set the image will just have one
+*    luminance (grayscale) component.
+*
+* PNG_FORMAT_FLAG_ALPHA: if set each pixel in the image will have an additional
+*    alpha value; a linear value that describes the degree the image pixel
+*    covers (overwrites) the contents of the existing pixel on the display.
+*
+* PNG_FORMAT_FLAG_LINEAR: if set the components of each pixel will be returned
+*    as a series of 16-bit linear values, if not set the components will be
+*    returned as a series of 8-bit values encoded according to the 'sRGB'
+*    standard.  The 8-bit format is the normal format for images intended for
+*    direct display, because almost all display devices do the inverse of the
+*    sRGB transformation to the data they receive.  The 16-bit format is more
+*    common for scientific data and image data that must be further processed;
+*    because it is linear simple math can be done on the component values.
+*    Regardless of the setting of this flag the alpha channel is always linear,
+*    although it will be 8 bits or 16 bits wide as specified by the flag.
+*
+* PNG_FORMAT_FLAG_BGR: if set the components of a color pixel will be returned
+*    in the order blue, then green, then red.  If not set the pixel components
+*    are in the order red, then green, then blue.
+*
+* PNG_FORMAT_FLAG_AFIRST: if set the alpha channel (if present) precedes the
+*    color or grayscale components.  If not set the alpha channel follows the
+*    components.
+*
+* You do not have to read directly from a file.  You can read from memory or,
+* on systems that support it, from a <stdio.h> FILE*.  This is controlled by
+* the particular png_image_read_from_ function you call at the start.  Likewise
+* on write you can write to a FILE* if your system supports it.  Check the
+* macro PNG_STDIO_SUPPORTED to see if stdio support has been included in your
+* libpng build.
+*
+* If you read 16-bit (PNG_FORMAT_FLAG_LINEAR) data you may need to write it in
+* the 8-bit format for display.  You do this by setting the convert_to_8bit
+* flag to 'true'.
+*
+* Don't repeatedly convert between the 8-bit and 16-bit forms.  There is
+* significant data loss when 16-bit data is converted to the 8-bit encoding and
+* the current libpng implementation of convertion to 16-bit is also
+* significantly lossy.  The latter will be fixed in the future, but the former
+* is unavoidable - the 8-bit format just doesn't have enough resolution.
+*/
+/* If your program needs more information from the PNG data it reads, or if you
+* need to do more complex transformations, or minimise transformations, on the
+* data you read, then you must use one of the several lower level libpng
+* interfaces.
+*
+* All these interfaces require that you do your own error handling - your
+* program must be able to arrange for control to return to your own code any
+* time libpng encounters a problem.  There are several ways to do this, but the
+* standard way is to use the ANSI-C (C90) <setjmp.h> interface to establish a
+* return point within your own code.  You must do this if you do not use the
+* simplified interface (above).
+*
+* The first step is to include the header files you need, including the libpng
+* header file.  Include any standard headers and feature test macros your
+* program requires before including png.h:
+*/
+#include <png.h>
+/* The png_jmpbuf() macro, used in error handling, became available in
+* libpng version 1.0.6.  If you want to be able to run your code with older
+* versions of libpng, you must define the macro yourself (but only if it
+* is not already defined by libpng!).
+*/
+#ifndef png_jmpbuf
+#  define png_jmpbuf(png_ptr) ((png_ptr)->png_jmpbuf)
+#endif
+/* Check to see if a file is a PNG file using png_sig_cmp().  png_sig_cmp()
+* returns zero if the image is a PNG and nonzero if it isn't a PNG.
+*
+* The function check_if_png() shown here, but not used, returns nonzero (true)
+* if the file can be opened and is a PNG, 0 (false) otherwise.
+*
+* If this call is successful, and you are going to keep the file open,
+* you should call png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK); once
+* you have created the png_ptr, so that libpng knows your application
+* has read that many bytes from the start of the file.  Make sure you
+* don't call png_set_sig_bytes() with more than 8 bytes read or give it
+* an incorrect number of bytes read, or you will either have read too
+* many bytes (your fault), or you are telling libpng to read the wrong
+* number of magic bytes (also your fault).
+*
+* Many applications already read the first 2 or 4 bytes from the start
+* of the image to determine the file type, so it would be easiest just
+* to pass the bytes to png_sig_cmp() or even skip that if you know
+* you have a PNG file, and call png_set_sig_bytes().
+*/
+#define PNG_BYTES_TO_CHECK 4
+int check_if_png(char *file_name, FILE **fp)
+{
+char buf[PNG_BYTES_TO_CHECK];
+/* Open the prospective PNG file. */
+if ((*fp = fopen(file_name, "rb")) == NULL)
+return 0;
+/* Read in some of the signature bytes */
+if (fread(buf, 1, PNG_BYTES_TO_CHECK, *fp) != PNG_BYTES_TO_CHECK)
+return 0;
+/* Compare the first PNG_BYTES_TO_CHECK bytes of the signature.
+Return nonzero (true) if they match */
+return(!png_sig_cmp(buf, (png_size_t)0, PNG_BYTES_TO_CHECK));
+}
+/* Read a PNG file.  You may want to return an error code if the read
+* fails (depending upon the failure).  There are two "prototypes" given
+* here - one where we are given the filename, and we need to open the
+* file, and the other where we are given an open file (possibly with
+* some or all of the magic bytes read - see comments above).
+*/
+#ifdef open_file /* prototype 1 */
+void read_png(char *file_name)  /* We need to open the file */
+{
+png_structp png_ptr;
+png_infop info_ptr;
+unsigned int sig_read = 0;
+png_uint_32 width, height;
+int bit_depth, color_type, interlace_type;
+FILE *fp;
+if ((fp = fopen(file_name, "rb")) == NULL)
+return (ERROR);
+#else no_open_file /* prototype 2 */
+void read_png(FILE *fp, unsigned int sig_read)  /* File is already open */
+{
+png_structp png_ptr;
+png_infop info_ptr;
+png_uint_32 width, height;
+int bit_depth, color_type, interlace_type;
+#endif no_open_file /* Only use one prototype! */
+/* 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 supply the
+* the compiler header file version, so that we know if the application
+* was compiled with a compatible version of the library.  REQUIRED
+*/
+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)
+{
+fclose(fp);
+return (ERROR);
+}
+/* Allocate/initialize the memory for image information.  REQUIRED. */
+info_ptr = png_create_info_struct(png_ptr);
+if (info_ptr == NULL)
+{
+fclose(fp);
+png_destroy_read_struct(&png_ptr, NULL, NULL);
+return (ERROR);
+}
+/* Set error handling if you are using the setjmp/longjmp method (this is
+* the normal method of doing things with libpng).  REQUIRED unless you
+* set up your own error handlers in the png_create_read_struct() earlier.
+*/
+if (setjmp(png_jmpbuf(png_ptr)))
+{
+/* Free all of the memory associated with the png_ptr and info_ptr */
+png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+fclose(fp);
+/* If we get here, we had a problem reading the file */
+return (ERROR);
+}
+/* One of the following I/O initialization methods is REQUIRED */
+#ifdef streams /* PNG file I/O method 1 */
+/* Set up the input control if you are using standard C streams */
+png_init_io(png_ptr, fp);
+#else no_streams /* PNG file I/O method 2 */
+/* If you are using replacement read functions, instead of calling
+* png_init_io() here you would call:
+*/
+png_set_read_fn(png_ptr, (void *)user_io_ptr, user_read_fn);
+/* where user_io_ptr is a structure you want available to the callbacks */
+#endif no_streams /* Use only one I/O method! */
+/* If we have already read some of the signature */
+png_set_sig_bytes(png_ptr, sig_read);
+#ifdef hilevel
+/*
+* If you have enough memory to read in the entire image at once,
+* and you need to specify only transforms that can be controlled
+* with one of the PNG_TRANSFORM_* bits (this presently excludes
+* quantizing, filling, setting background, and doing gamma
+* adjustment), then you can read the entire image (including
+* pixels) into the info structure with this call:
+*/
+png_read_png(png_ptr, info_ptr, png_transforms, NULL);
+#else
+/* OK, you're doing it the hard way, with the lower-level functions */
+/* The call to png_read_info() gives us all of the information from the
+* PNG file before the first IDAT (image data chunk).  REQUIRED
+*/
+png_read_info(png_ptr, info_ptr);
+png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
+&interlace_type, NULL, NULL);
+/* Set up the data transformations you want.  Note that these are all
+* optional.  Only call them if you want/need them.  Many of the
+* transformations only work on specific types of images, and many
+* are mutually exclusive.
+*/
+/* Tell libpng to strip 16 bit/color files down to 8 bits/color.
+* Use accurate scaling if it's available, otherwise just chop off the
+* low byte.
+*/
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+png_set_scale_16(png_ptr);
+#else
+png_set_strip_16(png_ptr);
+#endif
+/* Strip alpha bytes from the input data without combining with the
+* background (not recommended).
+*/
+png_set_strip_alpha(png_ptr);
+/* Extract multiple pixels with bit depths of 1, 2, and 4 from a single
+* byte into separate bytes (useful for paletted and grayscale images).
+*/
+png_set_packing(png_ptr);
+/* Change the order of packed pixels to least significant bit first
+* (not useful if you are using png_set_packing). */
+png_set_packswap(png_ptr);
+/* Expand paletted colors into true RGB triplets */
+if (color_type == PNG_COLOR_TYPE_PALETTE)
+png_set_palette_to_rgb(png_ptr);
+/* Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */
+if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
+png_set_expand_gray_1_2_4_to_8(png_ptr);
+/* Expand paletted or RGB images with transparency to full alpha channels
+* so the data will be available as RGBA quartets.
+*/
+if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
+png_set_tRNS_to_alpha(png_ptr);
+/* Set the background color to draw transparent and alpha images over.
+* It is possible to set the red, green, and blue components directly
+* for paletted images instead of supplying a palette index.  Note that
+* even if the PNG file supplies a background, you are not required to
+* use it - you should use the (solid) application background if it has one.
+*/
+png_color_16 my_background, *image_background;
+if (png_get_bKGD(png_ptr, info_ptr, &image_background))
+png_set_background(png_ptr, image_background,
+PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
+else
+png_set_background(png_ptr, &my_background,
+PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
+/* Some suggestions as to how to get a screen gamma value
+*
+* Note that screen gamma is the display_exponent, which includes
+* the CRT_exponent and any correction for viewing conditions
+*/
+if (/* We have a user-defined screen gamma value */)
+{
+screen_gamma = user-defined screen_gamma;
+}
+/* This is one way that applications share the same screen gamma value */
+else if ((gamma_str = getenv("SCREEN_GAMMA")) != NULL)
+{
+screen_gamma = atof(gamma_str);
+}
+/* If we don't have another value */
+else
+{
+screen_gamma = PNG_DEFAULT_sRGB;  /* A good guess for a PC monitor
+in a dimly lit room */
+screen_gamma = PNG_GAMMA_MAC_18 or 1.0; /* Good guesses for Mac systems */
+}
+/* Tell libpng to handle the gamma conversion for you.  The final call
+* is a good guess for PC generated images, but it should be configurable
+* by the user at run time by the user.  It is strongly suggested that
+* your application support gamma correction.
+*/
+int intent;
+if (png_get_sRGB(png_ptr, info_ptr, &intent))
+png_set_gamma(png_ptr, screen_gamma, PNG_DEFAULT_sRGB);
+else
+{
+double image_gamma;
+if (png_get_gAMA(png_ptr, info_ptr, &image_gamma))
+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)
+{
+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))
+{
+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 /* PNG_READ_QUANTIZE_SUPPORTED */
+/* 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))
+{
+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)
+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, 0xff, 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
+number_passes = 1;
+#endif /* PNG_READ_INTERLACING_SUPPORTED */
+/* 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 (ie 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. */
+/* The easiest way to read the image: */
+png_bytep row_pointers[height];
+/* Clear the pointer array */
+for (row = 0; row < height; row++)
+row_pointers[row] = NULL;
+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);
+}
+/* This one's new.  You will need to provide all three
+* function callbacks, even if you aren't using them all.
+* 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);
+}
+/* This one's new also.  Simply give it 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 /* PNG_READ_INTERLACING_SUPPORTED */
+}
+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 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() here 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 malloced.  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
+* chunks 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, 2, 4 bit packed pixel formats */
+png_set_packswap(png_ptr);
+/* Turn on interlace handling if you are not using png_write_image() */
+if (interlacing)
+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 */
+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 recommended 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, thus
+* avoiding the double-free security problem.
+*/
+/* Clean up after the write, and free any memory allocated */
+png_destroy_write_struct(&png_ptr, &info_ptr);
+/* Close the file */
+fclose(fp);
+/* That's it */
+return (OK);
+}
+#endif /* if 0 */

Mercurial > mm7

comparison lib/libpng/example.c @ 2305:a5e8eecac226