diff options
Diffstat (limited to 'libpng/example.c')
| -rw-r--r-- | libpng/example.c | 436 |
1 files changed, 205 insertions, 231 deletions
diff --git a/libpng/example.c b/libpng/example.c index 99d2f054..2e2afaaf 100644 --- a/libpng/example.c +++ b/libpng/example.c @@ -2,18 +2,20 @@ #if 0 /* in case someone actually tries to compile this */ /* example.c - an example of using libpng - * Last changed in libpng 1.6.24 [August 4, 2016] + * + * Maintained 2018 Cosmin Truta * Maintained 1998-2016 Glenn Randers-Pehrson - * Maintained 1996, 1997 Andreas Dilger) - * Written 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) + * 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 work is published from: United States, Canada. */ /* 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 + * 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. * @@ -24,16 +26,17 @@ * 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 +/* The simple, but restricted approach to reading a PNG file or data stream + * requires just two function calls, as in the following complete program. + * Writing a file needs just 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 + * potentially new format, to a new file. While this code will compile, there + * is minimal (insufficient) error checking. For a more realistic version, + * see contrib/examples/pngtopng.c */ + #include <stddef.h> #include <stdlib.h> #include <string.h> @@ -68,28 +71,28 @@ int main(int argc, const char **argv) */ 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 + /* 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. + * 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 + * 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 + * 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: + * all images into an index/color-mapped format, then you can use: * * PNG_IMAGE_COLORMAP_SIZE(image) * @@ -111,17 +114,15 @@ int main(int argc, const char **argv) exit(0); } } - else { /* Calling png_image_free 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: + * 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_image_free(&image); - else free(buffer); } @@ -130,65 +131,67 @@ int main(int argc, const char **argv) * textual message in the 'png_image' structure: */ fprintf(stderr, "pngtopng: error: %s\n", image.message); - exit (1); + exit(1); } fprintf(stderr, "pngtopng: usage: pngtopng input-file output-file\n"); - exit(1); + exit(2); } /* 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. + * 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): + * 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 + * 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_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_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_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 + * 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. + * 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 + * 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 conversion to 16-bit is also + * significant data loss when 16-bit data is converted to the 8-bit encoding, + * and the current libpng implementation of conversion 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. */ @@ -199,10 +202,10 @@ int main(int argc, const char **argv) * 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 + * 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 <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 @@ -214,7 +217,7 @@ int main(int argc, const char **argv) /* 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!). + * is not already defined by libpng!) */ #ifndef png_jmpbuf @@ -222,10 +225,10 @@ int main(int argc, const char **argv) #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. + * returns zero if the image is a PNG, and nonzero otherwise. * * 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 the file can be opened and is a PNG, and 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 @@ -238,7 +241,7 @@ int main(int argc, const char **argv) * * 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 + * 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 @@ -250,14 +253,14 @@ int check_if_png(char *file_name, FILE **fp) if ((*fp = fopen(file_name, "rb")) == NULL) return 0; - /* Read in some of the signature bytes */ + /* 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)); + * Return nonzero (true) if they match. + */ + return(!png_sig_cmp(buf, 0, PNG_BYTES_TO_CHECK)); } /* Read a PNG file. You may want to return an error code if the read @@ -267,7 +270,7 @@ int check_if_png(char *file_name, FILE **fp) * 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 */ +void read_png(char *file_name) /* We need to open the file */ { png_structp png_ptr; png_infop info_ptr; @@ -280,7 +283,7 @@ void read_png(char *file_name) /* We need to open the file */ return (ERROR); #else no_open_file /* prototype 2 */ -void read_png(FILE *fp, int sig_read) /* File is already open */ +void read_png(FILE *fp, int sig_read) /* File is already open */ { png_structp png_ptr; png_infop info_ptr; @@ -292,7 +295,7 @@ void read_png(FILE *fp, int sig_read) /* File is already open */ * 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 + * 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); @@ -316,35 +319,33 @@ void read_png(FILE *fp, int sig_read) /* File is already open */ * 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 */ + /* 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 */ + /* If we get here, we had a problem reading the file. */ return (ERROR); } - /* One of the following I/O initialization methods is REQUIRED */ + /* 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 */ + /* 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_init_io(), 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 */ + /* 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, + /* 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 @@ -354,10 +355,10 @@ void read_png(FILE *fp, int sig_read) /* File is already open */ png_read_png(png_ptr, info_ptr, png_transforms, NULL); #else - /* OK, you're doing it the hard way, with the lower-level functions */ + /* 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 file before the first IDAT (image data chunk). REQUIRED. */ png_read_info(png_ptr, info_ptr); @@ -385,20 +386,21 @@ void read_png(FILE *fp, int sig_read) /* File is already open */ */ png_set_strip_alpha(png_ptr); - /* Extract multiple pixels with bit depths of 1, 2, and 4 from a single + /* Extract multiple pixels with bit depths of 1, 2 or 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). */ + * (not useful if you are using png_set_packing). + */ png_set_packswap(png_ptr); - /* Expand paletted colors into true RGB triplets */ + /* 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 */ + /* 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); @@ -409,12 +411,11 @@ void read_png(FILE *fp, int sig_read) /* File is already open */ 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 + * 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) != 0) @@ -424,32 +425,29 @@ void read_png(FILE *fp, int sig_read) /* File is already open */ 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 + /* 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 + * 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 */ + /* 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 */ + 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. + * by the user at run time. Gamma correction support in your application + * is strongly recommended. */ int intent; @@ -466,7 +464,7 @@ void read_png(FILE *fp, int sig_read) /* File is already open */ } #ifdef PNG_READ_QUANTIZE_SUPPORTED - /* Quantize RGB files down to 8-bit palette or reduce palettes + /* 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) @@ -474,29 +472,26 @@ void read_png(FILE *fp, int sig_read) /* File is already open */ int num_palette; png_colorp palette; - /* This reduces the image to the application supplied 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 */ + /* 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 */ + /* 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 */ + /* 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 @@ -506,22 +501,21 @@ void read_png(FILE *fp, int sig_read) /* File is already open */ 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) */ + /* 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) */ + /* 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 */ + /* 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) */ + /* Add filler (or alpha) byte (before/after each RGB triplet). */ png_set_filler(png_ptr, 0xffff, PNG_FILLER_AFTER); #ifdef PNG_READ_INTERLACING_SUPPORTED @@ -534,40 +528,31 @@ void read_png(FILE *fp, int sig_read) /* File is already open */ 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 (ie you selected such a transform above). + * 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. */ - - /* 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; - + 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 */ + /* 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) @@ -581,24 +566,24 @@ void read_png(FILE *fp, int sig_read) /* File is already open */ #endif no_sparkle /* Use only one of these two methods */ } - /* If you want to display the image after every pass, do so here */ + /* 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 */ + /* 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 */ + /* At this point you have read the entire image. */ - /* Clean up after the read, and free any memory allocated - REQUIRED */ + /* Clean up after the read, and free any memory allocated. REQUIRED. */ png_destroy_read_struct(&png_ptr, &info_ptr, NULL); - /* Close the file */ + /* Close the file. */ fclose(fp); - /* That's it */ + /* That's it! */ return (OK); } @@ -610,34 +595,30 @@ 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 + * 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. + /* 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(). @@ -650,7 +631,6 @@ initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr) */ png_set_progressive_read_fn(*png_ptr, (void *)stream_data, info_callback, row_callback, end_callback); - return (OK); } @@ -660,18 +640,18 @@ process_data(png_structp *png_ptr, png_infop *info_ptr, { if (setjmp(png_jmpbuf((*png_ptr)))) { - /* Free the png_ptr and info_ptr memory on error */ + /* 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). + /* 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 + * 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 + * 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. */ @@ -693,8 +673,7 @@ info_callback(png_structp png_ptr, png_infop info) 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 + /* 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. * @@ -705,25 +684,22 @@ row_callback(png_structp png_ptr, png_bytep new_row, * 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 + * 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. - */ + /* 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 + /* 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); + 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 + /* 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. * @@ -734,7 +710,6 @@ row_callback(png_structp png_ptr, png_bytep new_row, * (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 @@ -781,14 +756,13 @@ void write_png(char *file_name /* , ... other image information ... */) */ 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 */ + /* Allocate/initialize the image information data. REQUIRED. */ info_ptr = png_create_info_struct(png_ptr); if (info_ptr == NULL) { @@ -797,30 +771,30 @@ void write_png(char *file_name /* , ... other image information ... */) return (ERROR); } - /* Set error handling. REQUIRED if you aren't supplying your own + /* 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 */ + /* 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 */ + /* 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 */ + /* 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_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 */ + /* where user_io_ptr is a structure you want available to the callbacks. */ #endif no_streams /* Only use one initialization method */ #ifdef hilevel @@ -831,30 +805,32 @@ void write_png(char *file_name /* , ... other image information ... */) png_write_png(png_ptr, info_ptr, png_transforms, NULL); #else - /* This is the hard way */ + /* 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, + * 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 + * 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); + 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 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 + /* 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 */ + /* Optional significant bit (sBIT) chunk. */ png_color_8 sig_bit; /* If we are dealing with a grayscale image then */ @@ -870,18 +846,17 @@ void write_png(char *file_name /* , ... other image information ... */) 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 */ + /* Optionally write comments into the image. */ { png_text text_ptr[3]; - char key0[]="Title"; - char text0[]="Mona Lisa"; + 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; @@ -889,8 +864,8 @@ void write_png(char *file_name /* , ... other image information ... */) text_ptr[0].lang = NULL; text_ptr[0].lang_key = NULL; - char key1[]="Author"; - char text1[]="Leonardo DaVinci"; + 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; @@ -898,8 +873,8 @@ void write_png(char *file_name /* , ... other image information ... */) text_ptr[1].lang = NULL; text_ptr[1].lang_key = NULL; - char key2[]="Description"; - char text2[]="<long text>"; + 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; @@ -910,14 +885,14 @@ void write_png(char *file_name /* , ... other image information ... */) png_set_text(write_ptr, write_info_ptr, text_ptr, 3); } - /* Other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs */ + /* Other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs. */ - /* Note that if sRGB is present the gAMA and cHRM chunks must be ignored + /* 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 + * be written in accordance with the sRGB profile. */ - /* Write the file header information. REQUIRED */ + /* 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 @@ -941,7 +916,7 @@ void write_png(char *file_name /* , ... other image information ... */) * all optional. Only call them if you want them. */ - /* Invert monochrome pixels */ + /* Invert monochrome pixels. */ png_set_invert_mono(png_ptr); /* Shift the pixels up to a legal bit depth and fill in @@ -949,30 +924,29 @@ void write_png(char *file_name /* , ... other image information ... */) */ png_set_shift(png_ptr, &sig_bit); - /* Pack pixels into bytes */ + /* Pack pixels into bytes. */ png_set_packing(png_ptr); - /* Swap location of alpha bytes from ARGB to RGBA */ + /* 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. + * 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 */ + /* Flip BGR pixels to RGB. */ png_set_bgr(png_ptr); - /* Swap bytes of 16-bit files to most significant byte first */ + /* 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 */ + /* 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() */ + /* 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; @@ -982,29 +956,28 @@ void write_png(char *file_name /* , ... other image information ... */) */ png_uint_32 k, height, width; - /* In this example, "image" is a one-dimensional array of bytes */ + /* 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]; + /* 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"); + 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 */ + /* Set up pointers into your "image" byte array. */ for (k = 0; k < height; k++) - row_pointers[k] = image + k*width*bytes_per_pixel; + row_pointers[k] = image + k * width * bytes_per_pixel; - /* One of the following output methods is REQUIRED */ + /* 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 */ + /* The other way to write the image - deal with interlacing. */ #else no_entire /* Write out the image data by one or more scanlines */ @@ -1016,27 +989,27 @@ void write_png(char *file_name /* , ... other image information ... */) /* 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 */ + /* 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 + * 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 */ + /* 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(). + /* 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; @@ -1047,19 +1020,20 @@ void write_png(char *file_name /* , ... other image information ... */) */ png_free(png_ptr, trans); trans = NULL; - /* Whenever you use png_free() it is a good idea to set the pointer to + + /* 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. + * again. When png_free() sees a NULL it returns without action, avoiding + * the double-free problem. */ - /* Clean up after the write, and free any memory allocated */ + /* Clean up after the write, and free any allocated memory. */ png_destroy_write_struct(&png_ptr, &info_ptr); - /* Close the file */ + /* Close the file. */ fclose(fp); - /* That's it */ + /* That's it! */ return (OK); } |