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diff --git a/png/example.c b/png/example.c new file mode 100644 index 0000000..e9747a8 --- /dev/null +++ b/png/example.c @@ -0,0 +1,1061 @@ + +#if 0 /* in case someone actually tries to compile this */ + +/* example.c - an example of using libpng + * Last changed in libpng 1.6.11 [June 12, 2014] + * Maintained 1998-2014 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 != 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 */ + 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 */ |