--- /dev/null
+
+#if 0 /* in case someone actually tries to compile this */
+
+/* example.c - an example of using libpng */
+
+/* This is an example of how to use libpng to read and write PNG files.
+ * The file libpng.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.
+ */
+
+#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)->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, png_infopp_NULL, png_infopp_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, png_infopp_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
+ * dithering, 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, png_voidp_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, int_p_NULL, int_p_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 */
+ png_set_strip_16(png_ptr);
+
+ /* 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_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_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 = 2.2; /* A good guess for a PC monitors in a dimly
+ lit room */
+ screen_gamma = 1.7 or 1.0; /* A good guess 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, 0.45455);
+ 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);
+ }
+
+ /* Dither 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 dithered */
+ png_color std_color_cube[MAX_SCREEN_COLORS];
+
+ png_set_dither(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
+ MAX_SCREEN_COLORS, png_uint_16p_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_dither(png_ptr, palette, num_palette,
+ max_screen_colors, histogram, 0);
+ }
+ }
+
+ /* 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;
+
+ png_get_sBIT(png_ptr, info_ptr, &sig_bit);
+ png_set_shift(png_ptr, sig_bit);
+ }
+
+ /* 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);
+
+ /* 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);
+
+ /* 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];
+
+ 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], png_bytepp_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], png_bytepp_NULL,
+ number_of_rows);
+#else no_sparkle /* Read the image using the "rectangle" effect */
+ png_read_rows(png_ptr, png_bytepp_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, png_infopp_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, png_infopp_NULL);
+ return (ERROR);
+ }
+
+ if (setjmp(png_jmpbuf((*png_ptr))))
+ {
+ png_destroy_read_struct(png_ptr, info_ptr, png_infopp_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, png_infopp_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:
+ */
+ /* Check if row_num is in bounds. */
+ if((row_num >= 0) && (row_num < height))
+ {
+ /* Get pointer to corresponding row in our
+ * PNG read buffer.
+ */
+ png_bytep old_row = ((png_bytep *)our_data)[row_num];
+
+ /* 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 png_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.
+ */
+}
+
+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, png_infopp_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 reading 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 read 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 info in the structure. You could "|" many
+ * PNG_TRANSFORM flags into the png_transforms integer here.
+ */
+ png_write_png(png_ptr, info_ptr, png_transforms, png_voidp_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 chunk */
+ /* 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 */
+ text_ptr[0].key = "Title";
+ text_ptr[0].text = "Mona Lisa";
+ text_ptr[0].compression = PNG_TEXT_COMPRESSION_NONE;
+ text_ptr[1].key = "Author";
+ text_ptr[1].text = "Leonardo DaVinci";
+ text_ptr[1].compression = PNG_TEXT_COMPRESSION_NONE;
+ text_ptr[2].key = "Description";
+ text_ptr[2].text = "<long text>";
+ text_ptr[2].compression = PNG_TEXT_COMPRESSION_zTXt;
+#ifdef PNG_iTXt_SUPPORTED
+ text_ptr[0].lang = NULL;
+ text_ptr[1].lang = NULL;
+ text_ptr[2].lang = NULL;
+#endif
+ png_set_text(png_ptr, 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 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 1.1.0
+ * 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;
+ png_byte image[height][width*bytes_per_pixel];
+ png_bytep row_pointers[height];
+ 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 1.1.0 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;
+
+ /* 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 */
projects / synfig.git / blobdiff