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tetex-bin  3.0
example.c
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00001 
00002 #if 0 /* in case someone actually tries to compile this */
00003 
00004 /* example.c - an example of using libpng */
00005 
00006 /* This is an example of how to use libpng to read and write PNG files.
00007  * The file libpng.txt is much more verbose then this.  If you have not
00008  * read it, do so first.  This was designed to be a starting point of an
00009  * implementation.  This is not officially part of libpng, is hereby placed
00010  * in the public domain, and therefore does not require a copyright notice.
00011  *
00012  * This file does not currently compile, because it is missing certain
00013  * parts, like allocating memory to hold an image.  You will have to
00014  * supply these parts to get it to compile.  For an example of a minimal
00015  * working PNG reader/writer, see pngtest.c, included in this distribution;
00016  * see also the programs in the contrib directory.
00017  */
00018 
00019 #include "png.h"
00020 
00021  /* The png_jmpbuf() macro, used in error handling, became available in
00022   * libpng version 1.0.6.  If you want to be able to run your code with older
00023   * versions of libpng, you must define the macro yourself (but only if it
00024   * is not already defined by libpng!).
00025   */
00026 
00027 #ifndef png_jmpbuf
00028 #  define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf)
00029 #endif
00030 
00031 /* Check to see if a file is a PNG file using png_sig_cmp().  png_sig_cmp()
00032  * returns zero if the image is a PNG and nonzero if it isn't a PNG.
00033  *
00034  * The function check_if_png() shown here, but not used, returns nonzero (true)
00035  * if the file can be opened and is a PNG, 0 (false) otherwise.
00036  *
00037  * If this call is successful, and you are going to keep the file open,
00038  * you should call png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK); once
00039  * you have created the png_ptr, so that libpng knows your application
00040  * has read that many bytes from the start of the file.  Make sure you
00041  * don't call png_set_sig_bytes() with more than 8 bytes read or give it
00042  * an incorrect number of bytes read, or you will either have read too
00043  * many bytes (your fault), or you are telling libpng to read the wrong
00044  * number of magic bytes (also your fault).
00045  *
00046  * Many applications already read the first 2 or 4 bytes from the start
00047  * of the image to determine the file type, so it would be easiest just
00048  * to pass the bytes to png_sig_cmp() or even skip that if you know
00049  * you have a PNG file, and call png_set_sig_bytes().
00050  */
00051 #define PNG_BYTES_TO_CHECK 4
00052 int check_if_png(char *file_name, FILE **fp)
00053 {
00054    char buf[PNG_BYTES_TO_CHECK];
00055 
00056    /* Open the prospective PNG file. */
00057    if ((*fp = fopen(file_name, "rb")) == NULL)
00058       return 0;
00059 
00060    /* Read in some of the signature bytes */
00061    if (fread(buf, 1, PNG_BYTES_TO_CHECK, *fp) != PNG_BYTES_TO_CHECK)
00062       return 0;
00063 
00064    /* Compare the first PNG_BYTES_TO_CHECK bytes of the signature.
00065       Return nonzero (true) if they match */
00066 
00067    return(!png_sig_cmp(buf, (png_size_t)0, PNG_BYTES_TO_CHECK));
00068 }
00069 
00070 /* Read a PNG file.  You may want to return an error code if the read
00071  * fails (depending upon the failure).  There are two "prototypes" given
00072  * here - one where we are given the filename, and we need to open the
00073  * file, and the other where we are given an open file (possibly with
00074  * some or all of the magic bytes read - see comments above).
00075  */
00076 #ifdef open_file /* prototype 1 */
00077 void read_png(char *file_name)  /* We need to open the file */
00078 {
00079    png_structp png_ptr;
00080    png_infop info_ptr;
00081    unsigned int sig_read = 0;
00082    png_uint_32 width, height;
00083    int bit_depth, color_type, interlace_type;
00084    FILE *fp;
00085 
00086    if ((fp = fopen(file_name, "rb")) == NULL)
00087       return (ERROR);
00088 #else no_open_file /* prototype 2 */
00089 void read_png(FILE *fp, unsigned int sig_read)  /* file is already open */
00090 {
00091    png_structp png_ptr;
00092    png_infop info_ptr;
00093    png_uint_32 width, height;
00094    int bit_depth, color_type, interlace_type;
00095 #endif no_open_file /* only use one prototype! */
00096 
00097    /* Create and initialize the png_struct with the desired error handler
00098     * functions.  If you want to use the default stderr and longjump method,
00099     * you can supply NULL for the last three parameters.  We also supply the
00100     * the compiler header file version, so that we know if the application
00101     * was compiled with a compatible version of the library.  REQUIRED
00102     */
00103    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
00104       png_voidp user_error_ptr, user_error_fn, user_warning_fn);
00105 
00106    if (png_ptr == NULL)
00107    {
00108       fclose(fp);
00109       return (ERROR);
00110    }
00111 
00112    /* Allocate/initialize the memory for image information.  REQUIRED. */
00113    info_ptr = png_create_info_struct(png_ptr);
00114    if (info_ptr == NULL)
00115    {
00116       fclose(fp);
00117       png_destroy_read_struct(&png_ptr, png_infopp_NULL, png_infopp_NULL);
00118       return (ERROR);
00119    }
00120 
00121    /* Set error handling if you are using the setjmp/longjmp method (this is
00122     * the normal method of doing things with libpng).  REQUIRED unless you
00123     * set up your own error handlers in the png_create_read_struct() earlier.
00124     */
00125 
00126    if (setjmp(png_jmpbuf(png_ptr)))
00127    {
00128       /* Free all of the memory associated with the png_ptr and info_ptr */
00129       png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
00130       fclose(fp);
00131       /* If we get here, we had a problem reading the file */
00132       return (ERROR);
00133    }
00134 
00135    /* One of the following I/O initialization methods is REQUIRED */
00136 #ifdef streams /* PNG file I/O method 1 */
00137    /* Set up the input control if you are using standard C streams */
00138    png_init_io(png_ptr, fp);
00139 
00140 #else no_streams /* PNG file I/O method 2 */
00141    /* If you are using replacement read functions, instead of calling
00142     * png_init_io() here you would call:
00143     */
00144    png_set_read_fn(png_ptr, (void *)user_io_ptr, user_read_fn);
00145    /* where user_io_ptr is a structure you want available to the callbacks */
00146 #endif no_streams /* Use only one I/O method! */
00147 
00148    /* If we have already read some of the signature */
00149    png_set_sig_bytes(png_ptr, sig_read);
00150 
00151 #ifdef hilevel
00152    /*
00153     * If you have enough memory to read in the entire image at once,
00154     * and you need to specify only transforms that can be controlled
00155     * with one of the PNG_TRANSFORM_* bits (this presently excludes
00156     * dithering, filling, setting background, and doing gamma
00157     * adjustment), then you can read the entire image (including
00158     * pixels) into the info structure with this call:
00159     */
00160    png_read_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL);
00161 #else
00162    /* OK, you're doing it the hard way, with the lower-level functions */
00163 
00164    /* The call to png_read_info() gives us all of the information from the
00165     * PNG file before the first IDAT (image data chunk).  REQUIRED
00166     */
00167    png_read_info(png_ptr, info_ptr);
00168 
00169    png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
00170        &interlace_type, int_p_NULL, int_p_NULL);
00171 
00172 /* Set up the data transformations you want.  Note that these are all
00173  * optional.  Only call them if you want/need them.  Many of the
00174  * transformations only work on specific types of images, and many
00175  * are mutually exclusive.
00176  */
00177 
00178    /* tell libpng to strip 16 bit/color files down to 8 bits/color */
00179    png_set_strip_16(png_ptr);
00180 
00181    /* Strip alpha bytes from the input data without combining with the
00182     * background (not recommended).
00183     */
00184    png_set_strip_alpha(png_ptr);
00185 
00186    /* Extract multiple pixels with bit depths of 1, 2, and 4 from a single
00187     * byte into separate bytes (useful for paletted and grayscale images).
00188     */
00189    png_set_packing(png_ptr);
00190 
00191    /* Change the order of packed pixels to least significant bit first
00192     * (not useful if you are using png_set_packing). */
00193    png_set_packswap(png_ptr);
00194 
00195    /* Expand paletted colors into true RGB triplets */
00196    if (color_type == PNG_COLOR_TYPE_PALETTE)
00197       png_set_palette_rgb(png_ptr);
00198 
00199    /* Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */
00200    if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
00201       png_set_gray_1_2_4_to_8(png_ptr);
00202 
00203    /* Expand paletted or RGB images with transparency to full alpha channels
00204     * so the data will be available as RGBA quartets.
00205     */
00206    if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
00207       png_set_tRNS_to_alpha(png_ptr);
00208 
00209    /* Set the background color to draw transparent and alpha images over.
00210     * It is possible to set the red, green, and blue components directly
00211     * for paletted images instead of supplying a palette index.  Note that
00212     * even if the PNG file supplies a background, you are not required to
00213     * use it - you should use the (solid) application background if it has one.
00214     */
00215 
00216    png_color_16 my_background, *image_background;
00217 
00218    if (png_get_bKGD(png_ptr, info_ptr, &image_background))
00219       png_set_background(png_ptr, image_background,
00220                          PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
00221    else
00222       png_set_background(png_ptr, &my_background,
00223                          PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
00224 
00225    /* Some suggestions as to how to get a screen gamma value */
00226 
00227    /* Note that screen gamma is the display_exponent, which includes
00228     * the CRT_exponent and any correction for viewing conditions */
00229    if (/* We have a user-defined screen gamma value */)
00230    {
00231       screen_gamma = user-defined screen_gamma;
00232    }
00233    /* This is one way that applications share the same screen gamma value */
00234    else if ((gamma_str = getenv("SCREEN_GAMMA")) != NULL)
00235    {
00236       screen_gamma = atof(gamma_str);
00237    }
00238    /* If we don't have another value */
00239    else
00240    {
00241       screen_gamma = 2.2;  /* A good guess for a PC monitors in a dimly
00242                               lit room */
00243       screen_gamma = 1.7 or 1.0;  /* A good guess for Mac systems */
00244    }
00245 
00246    /* Tell libpng to handle the gamma conversion for you.  The final call
00247     * is a good guess for PC generated images, but it should be configurable
00248     * by the user at run time by the user.  It is strongly suggested that
00249     * your application support gamma correction.
00250     */
00251 
00252    int intent;
00253 
00254    if (png_get_sRGB(png_ptr, info_ptr, &intent))
00255       png_set_gamma(png_ptr, screen_gamma, 0.45455);
00256    else
00257    {
00258       double image_gamma;
00259       if (png_get_gAMA(png_ptr, info_ptr, &image_gamma))
00260          png_set_gamma(png_ptr, screen_gamma, image_gamma);
00261       else
00262          png_set_gamma(png_ptr, screen_gamma, 0.45455);
00263    }
00264 
00265    /* Dither RGB files down to 8 bit palette or reduce palettes
00266     * to the number of colors available on your screen.
00267     */
00268    if (color_type & PNG_COLOR_MASK_COLOR)
00269    {
00270       int num_palette;
00271       png_colorp palette;
00272 
00273       /* This reduces the image to the application supplied palette */
00274       if (/* we have our own palette */)
00275       {
00276          /* An array of colors to which the image should be dithered */
00277          png_color std_color_cube[MAX_SCREEN_COLORS];
00278 
00279          png_set_dither(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
00280             MAX_SCREEN_COLORS, png_uint_16p_NULL, 0);
00281       }
00282       /* This reduces the image to the palette supplied in the file */
00283       else if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette))
00284       {
00285          png_uint_16p histogram = NULL;
00286 
00287          png_get_hIST(png_ptr, info_ptr, &histogram);
00288 
00289          png_set_dither(png_ptr, palette, num_palette,
00290                         max_screen_colors, histogram, 0);
00291       }
00292    }
00293 
00294    /* invert monochrome files to have 0 as white and 1 as black */
00295    png_set_invert_mono(png_ptr);
00296 
00297    /* If you want to shift the pixel values from the range [0,255] or
00298     * [0,65535] to the original [0,7] or [0,31], or whatever range the
00299     * colors were originally in:
00300     */
00301    if (png_get_valid(png_ptr, info_ptr, PNG_INFO_sBIT))
00302    {
00303       png_color_8p sig_bit;
00304 
00305       png_get_sBIT(png_ptr, info_ptr, &sig_bit);
00306       png_set_shift(png_ptr, sig_bit);
00307    }
00308 
00309    /* flip the RGB pixels to BGR (or RGBA to BGRA) */
00310    if (color_type & PNG_COLOR_MASK_COLOR)
00311       png_set_bgr(png_ptr);
00312 
00313    /* swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
00314    png_set_swap_alpha(png_ptr);
00315 
00316    /* swap bytes of 16 bit files to least significant byte first */
00317    png_set_swap(png_ptr);
00318 
00319    /* Add filler (or alpha) byte (before/after each RGB triplet) */
00320    png_set_filler(png_ptr, 0xff, PNG_FILLER_AFTER);
00321 
00322    /* Turn on interlace handling.  REQUIRED if you are not using
00323     * png_read_image().  To see how to handle interlacing passes,
00324     * see the png_read_row() method below:
00325     */
00326    number_passes = png_set_interlace_handling(png_ptr);
00327 
00328    /* Optional call to gamma correct and add the background to the palette
00329     * and update info structure.  REQUIRED if you are expecting libpng to
00330     * update the palette for you (ie you selected such a transform above).
00331     */
00332    png_read_update_info(png_ptr, info_ptr);
00333 
00334    /* Allocate the memory to hold the image using the fields of info_ptr. */
00335 
00336    /* The easiest way to read the image: */
00337    png_bytep row_pointers[height];
00338 
00339    for (row = 0; row < height; row++)
00340    {
00341       row_pointers[row] = png_malloc(png_ptr, png_get_rowbytes(png_ptr,
00342          info_ptr));
00343    }
00344 
00345    /* Now it's time to read the image.  One of these methods is REQUIRED */
00346 #ifdef entire /* Read the entire image in one go */
00347    png_read_image(png_ptr, row_pointers);
00348 
00349 #else no_entire /* Read the image one or more scanlines at a time */
00350    /* The other way to read images - deal with interlacing: */
00351 
00352    for (pass = 0; pass < number_passes; pass++)
00353    {
00354 #ifdef single /* Read the image a single row at a time */
00355       for (y = 0; y < height; y++)
00356       {
00357          png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL, 1);
00358       }
00359 
00360 #else no_single /* Read the image several rows at a time */
00361       for (y = 0; y < height; y += number_of_rows)
00362       {
00363 #ifdef sparkle /* Read the image using the "sparkle" effect. */
00364          png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL,
00365             number_of_rows);
00366 #else no_sparkle /* Read the image using the "rectangle" effect */
00367          png_read_rows(png_ptr, png_bytepp_NULL, &row_pointers[y],
00368             number_of_rows);
00369 #endif no_sparkle /* use only one of these two methods */
00370       }
00371 
00372       /* if you want to display the image after every pass, do
00373          so here */
00374 #endif no_single /* use only one of these two methods */
00375    }
00376 #endif no_entire /* use only one of these two methods */
00377 
00378    /* read rest of file, and get additional chunks in info_ptr - REQUIRED */
00379    png_read_end(png_ptr, info_ptr);
00380 #endif hilevel
00381 
00382    /* At this point you have read the entire image */
00383 
00384    /* clean up after the read, and free any memory allocated - REQUIRED */
00385    png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
00386 
00387    /* close the file */
00388    fclose(fp);
00389 
00390    /* that's it */
00391    return (OK);
00392 }
00393 
00394 /* progressively read a file */
00395 
00396 int
00397 initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr)
00398 {
00399    /* Create and initialize the png_struct with the desired error handler
00400     * functions.  If you want to use the default stderr and longjump method,
00401     * you can supply NULL for the last three parameters.  We also check that
00402     * the library version is compatible in case we are using dynamically
00403     * linked libraries.
00404     */
00405    *png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
00406        png_voidp user_error_ptr, user_error_fn, user_warning_fn);
00407 
00408    if (*png_ptr == NULL)
00409    {
00410       *info_ptr = NULL;
00411       return (ERROR);
00412    }
00413 
00414    *info_ptr = png_create_info_struct(png_ptr);
00415 
00416    if (*info_ptr == NULL)
00417    {
00418       png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL);
00419       return (ERROR);
00420    }
00421 
00422    if (setjmp(png_jmpbuf((*png_ptr))))
00423    {
00424       png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL);
00425       return (ERROR);
00426    }
00427 
00428    /* This one's new.  You will need to provide all three
00429     * function callbacks, even if you aren't using them all.
00430     * If you aren't using all functions, you can specify NULL
00431     * parameters.  Even when all three functions are NULL,
00432     * you need to call png_set_progressive_read_fn().
00433     * These functions shouldn't be dependent on global or
00434     * static variables if you are decoding several images
00435     * simultaneously.  You should store stream specific data
00436     * in a separate struct, given as the second parameter,
00437     * and retrieve the pointer from inside the callbacks using
00438     * the function png_get_progressive_ptr(png_ptr).
00439     */
00440    png_set_progressive_read_fn(*png_ptr, (void *)stream_data,
00441       info_callback, row_callback, end_callback);
00442 
00443    return (OK);
00444 }
00445 
00446 int
00447 process_data(png_structp *png_ptr, png_infop *info_ptr,
00448    png_bytep buffer, png_uint_32 length)
00449 {
00450    if (setjmp(png_jmpbuf((*png_ptr))))
00451    {
00452       /* Free the png_ptr and info_ptr memory on error */
00453       png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL);
00454       return (ERROR);
00455    }
00456 
00457    /* This one's new also.  Simply give it chunks of data as
00458     * they arrive from the data stream (in order, of course).
00459     * On Segmented machines, don't give it any more than 64K.
00460     * The library seems to run fine with sizes of 4K, although
00461     * you can give it much less if necessary (I assume you can
00462     * give it chunks of 1 byte, but I haven't tried with less
00463     * than 256 bytes yet).  When this function returns, you may
00464     * want to display any rows that were generated in the row
00465     * callback, if you aren't already displaying them there.
00466     */
00467    png_process_data(*png_ptr, *info_ptr, buffer, length);
00468    return (OK);
00469 }
00470 
00471 info_callback(png_structp png_ptr, png_infop info)
00472 {
00473 /* do any setup here, including setting any of the transformations
00474  * mentioned in the Reading PNG files section.  For now, you _must_
00475  * call either png_start_read_image() or png_read_update_info()
00476  * after all the transformations are set (even if you don't set
00477  * any).  You may start getting rows before png_process_data()
00478  * returns, so this is your last chance to prepare for that.
00479  */
00480 }
00481 
00482 row_callback(png_structp png_ptr, png_bytep new_row,
00483    png_uint_32 row_num, int pass)
00484 {
00485 /*
00486  * This function is called for every row in the image.  If the
00487  * image is interlaced, and you turned on the interlace handler,
00488  * this function will be called for every row in every pass.
00489  *
00490  * In this function you will receive a pointer to new row data from
00491  * libpng called new_row that is to replace a corresponding row (of
00492  * the same data format) in a buffer allocated by your application.
00493  * 
00494  * The new row data pointer new_row may be NULL, indicating there is
00495  * no new data to be replaced (in cases of interlace loading).
00496  * 
00497  * If new_row is not NULL then you need to call
00498  * png_progressive_combine_row() to replace the corresponding row as
00499  * shown below:
00500  */
00501    /* Check if row_num is in bounds. */
00502    if((row_num >= 0) && (row_num < height))
00503    {
00504      /* Get pointer to corresponding row in our
00505       * PNG read buffer.
00506       */
00507      png_bytep old_row = ((png_bytep *)our_data)[row_num];
00508 
00509      /* If both rows are allocated then copy the new row
00510       * data to the corresponding row data.
00511       */
00512      if((old_row != NULL) && (new_row != NULL))
00513      png_progressive_combine_row(png_ptr, old_row, new_row);
00514    }
00515 /*
00516  * The rows and passes are called in order, so you don't really
00517  * need the row_num and pass, but I'm supplying them because it
00518  * may make your life easier.
00519  *
00520  * For the non-NULL rows of interlaced images, you must call
00521  * png_progressive_combine_row() passing in the new row and the
00522  * old row, as demonstrated above.  You can call this function for
00523  * NULL rows (it will just return) and for non-interlaced images
00524  * (it just does the png_memcpy for you) if it will make the code
00525  * easier.  Thus, you can just do this for all cases:
00526  */
00527 
00528    png_progressive_combine_row(png_ptr, old_row, new_row);
00529 
00530 /* where old_row is what was displayed for previous rows.  Note
00531  * that the first pass (pass == 0 really) will completely cover
00532  * the old row, so the rows do not have to be initialized.  After
00533  * the first pass (and only for interlaced images), you will have
00534  * to pass the current row as new_row, and the function will combine
00535  * the old row and the new row.
00536  */
00537 }
00538 
00539 end_callback(png_structp png_ptr, png_infop info)
00540 {
00541 /* this function is called when the whole image has been read,
00542  * including any chunks after the image (up to and including
00543  * the IEND).  You will usually have the same info chunk as you
00544  * had in the header, although some data may have been added
00545  * to the comments and time fields.
00546  *
00547  * Most people won't do much here, perhaps setting a flag that
00548  * marks the image as finished.
00549  */
00550 }
00551 
00552 /* write a png file */
00553 void write_png(char *file_name /* , ... other image information ... */)
00554 {
00555    FILE *fp;
00556    png_structp png_ptr;
00557    png_infop info_ptr;
00558    png_colorp palette;
00559 
00560    /* open the file */
00561    fp = fopen(file_name, "wb");
00562    if (fp == NULL)
00563       return (ERROR);
00564 
00565    /* Create and initialize the png_struct with the desired error handler
00566     * functions.  If you want to use the default stderr and longjump method,
00567     * you can supply NULL for the last three parameters.  We also check that
00568     * the library version is compatible with the one used at compile time,
00569     * in case we are using dynamically linked libraries.  REQUIRED.
00570     */
00571    png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
00572       png_voidp user_error_ptr, user_error_fn, user_warning_fn);
00573 
00574    if (png_ptr == NULL)
00575    {
00576       fclose(fp);
00577       return (ERROR);
00578    }
00579 
00580    /* Allocate/initialize the image information data.  REQUIRED */
00581    info_ptr = png_create_info_struct(png_ptr);
00582    if (info_ptr == NULL)
00583    {
00584       fclose(fp);
00585       png_destroy_write_struct(&png_ptr,  png_infopp_NULL);
00586       return (ERROR);
00587    }
00588 
00589    /* Set error handling.  REQUIRED if you aren't supplying your own
00590     * error handling functions in the png_create_write_struct() call.
00591     */
00592    if (setjmp(png_jmpbuf(png_ptr)))
00593    {
00594       /* If we get here, we had a problem reading the file */
00595       fclose(fp);
00596       png_destroy_write_struct(&png_ptr, &info_ptr);
00597       return (ERROR);
00598    }
00599 
00600    /* One of the following I/O initialization functions is REQUIRED */
00601 #ifdef streams /* I/O initialization method 1 */
00602    /* set up the output control if you are using standard C streams */
00603    png_init_io(png_ptr, fp);
00604 #else no_streams /* I/O initialization method 2 */
00605    /* If you are using replacement read functions, instead of calling
00606     * png_init_io() here you would call */
00607    png_set_write_fn(png_ptr, (void *)user_io_ptr, user_write_fn,
00608       user_IO_flush_function);
00609    /* where user_io_ptr is a structure you want available to the callbacks */
00610 #endif no_streams /* only use one initialization method */
00611 
00612 #ifdef hilevel
00613    /* This is the easy way.  Use it if you already have all the
00614     * image info living info in the structure.  You could "|" many
00615     * PNG_TRANSFORM flags into the png_transforms integer here.
00616     */
00617    png_write_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL);
00618 #else
00619    /* This is the hard way */
00620 
00621    /* Set the image information here.  Width and height are up to 2^31,
00622     * bit_depth is one of 1, 2, 4, 8, or 16, but valid values also depend on
00623     * the color_type selected. color_type is one of PNG_COLOR_TYPE_GRAY,
00624     * PNG_COLOR_TYPE_GRAY_ALPHA, PNG_COLOR_TYPE_PALETTE, PNG_COLOR_TYPE_RGB,
00625     * or PNG_COLOR_TYPE_RGB_ALPHA.  interlace is either PNG_INTERLACE_NONE or
00626     * PNG_INTERLACE_ADAM7, and the compression_type and filter_type MUST
00627     * currently be PNG_COMPRESSION_TYPE_BASE and PNG_FILTER_TYPE_BASE. REQUIRED
00628     */
00629    png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, PNG_COLOR_TYPE_???,
00630       PNG_INTERLACE_????, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
00631 
00632    /* set the palette if there is one.  REQUIRED for indexed-color images */
00633    palette = (png_colorp)png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH
00634              * png_sizeof (png_color));
00635    /* ... set palette colors ... */
00636    png_set_PLTE(png_ptr, info_ptr, palette, PNG_MAX_PALETTE_LENGTH);
00637    /* You must not free palette here, because png_set_PLTE only makes a link to
00638       the palette that you malloced.  Wait until you are about to destroy
00639       the png structure. */
00640 
00641    /* optional significant bit chunk */
00642    /* if we are dealing with a grayscale image then */
00643    sig_bit.gray = true_bit_depth;
00644    /* otherwise, if we are dealing with a color image then */
00645    sig_bit.red = true_red_bit_depth;
00646    sig_bit.green = true_green_bit_depth;
00647    sig_bit.blue = true_blue_bit_depth;
00648    /* if the image has an alpha channel then */
00649    sig_bit.alpha = true_alpha_bit_depth;
00650    png_set_sBIT(png_ptr, info_ptr, sig_bit);
00651 
00652 
00653    /* Optional gamma chunk is strongly suggested if you have any guess
00654     * as to the correct gamma of the image.
00655     */
00656    png_set_gAMA(png_ptr, info_ptr, gamma);
00657 
00658    /* Optionally write comments into the image */
00659    text_ptr[0].key = "Title";
00660    text_ptr[0].text = "Mona Lisa";
00661    text_ptr[0].compression = PNG_TEXT_COMPRESSION_NONE;
00662    text_ptr[1].key = "Author";
00663    text_ptr[1].text = "Leonardo DaVinci";
00664    text_ptr[1].compression = PNG_TEXT_COMPRESSION_NONE;
00665    text_ptr[2].key = "Description";
00666    text_ptr[2].text = "<long text>";
00667    text_ptr[2].compression = PNG_TEXT_COMPRESSION_zTXt;
00668 #ifdef PNG_iTXt_SUPPORTED
00669    text_ptr[0].lang = NULL;
00670    text_ptr[1].lang = NULL;
00671    text_ptr[2].lang = NULL;
00672 #endif
00673    png_set_text(png_ptr, info_ptr, text_ptr, 3);
00674 
00675    /* other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs, */
00676    /* note that if sRGB is present the gAMA and cHRM chunks must be ignored
00677     * on read and must be written in accordance with the sRGB profile */
00678 
00679    /* Write the file header information.  REQUIRED */
00680    png_write_info(png_ptr, info_ptr);
00681 
00682    /* If you want, you can write the info in two steps, in case you need to
00683     * write your private chunk ahead of PLTE:
00684     *
00685     *   png_write_info_before_PLTE(write_ptr, write_info_ptr);
00686     *   write_my_chunk();
00687     *   png_write_info(png_ptr, info_ptr);
00688     *
00689     * However, given the level of known- and unknown-chunk support in 1.1.0
00690     * and up, this should no longer be necessary.
00691     */
00692 
00693    /* Once we write out the header, the compression type on the text
00694     * chunks gets changed to PNG_TEXT_COMPRESSION_NONE_WR or
00695     * PNG_TEXT_COMPRESSION_zTXt_WR, so it doesn't get written out again
00696     * at the end.
00697     */
00698 
00699    /* set up the transformations you want.  Note that these are
00700     * all optional.  Only call them if you want them.
00701     */
00702 
00703    /* invert monochrome pixels */
00704    png_set_invert_mono(png_ptr);
00705 
00706    /* Shift the pixels up to a legal bit depth and fill in
00707     * as appropriate to correctly scale the image.
00708     */
00709    png_set_shift(png_ptr, &sig_bit);
00710 
00711    /* pack pixels into bytes */
00712    png_set_packing(png_ptr);
00713 
00714    /* swap location of alpha bytes from ARGB to RGBA */
00715    png_set_swap_alpha(png_ptr);
00716 
00717    /* Get rid of filler (OR ALPHA) bytes, pack XRGB/RGBX/ARGB/RGBA into
00718     * RGB (4 channels -> 3 channels). The second parameter is not used.
00719     */
00720    png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
00721 
00722    /* flip BGR pixels to RGB */
00723    png_set_bgr(png_ptr);
00724 
00725    /* swap bytes of 16-bit files to most significant byte first */
00726    png_set_swap(png_ptr);
00727 
00728    /* swap bits of 1, 2, 4 bit packed pixel formats */
00729    png_set_packswap(png_ptr);
00730 
00731    /* turn on interlace handling if you are not using png_write_image() */
00732    if (interlacing)
00733       number_passes = png_set_interlace_handling(png_ptr);
00734    else
00735       number_passes = 1;
00736 
00737    /* The easiest way to write the image (you may have a different memory
00738     * layout, however, so choose what fits your needs best).  You need to
00739     * use the first method if you aren't handling interlacing yourself.
00740     */
00741    png_uint_32 k, height, width;
00742    png_byte image[height][width*bytes_per_pixel];
00743    png_bytep row_pointers[height];
00744 
00745    if (height > PNG_UINT_32_MAX/png_sizeof(png_bytep))
00746      png_error (png_ptr, "Image is too tall to process in memory");
00747 
00748    for (k = 0; k < height; k++)
00749      row_pointers[k] = image + k*width*bytes_per_pixel;
00750 
00751    /* One of the following output methods is REQUIRED */
00752 #ifdef entire /* write out the entire image data in one call */
00753    png_write_image(png_ptr, row_pointers);
00754 
00755    /* the other way to write the image - deal with interlacing */
00756 
00757 #else no_entire /* write out the image data by one or more scanlines */
00758    /* The number of passes is either 1 for non-interlaced images,
00759     * or 7 for interlaced images.
00760     */
00761    for (pass = 0; pass < number_passes; pass++)
00762    {
00763       /* Write a few rows at a time. */
00764       png_write_rows(png_ptr, &row_pointers[first_row], number_of_rows);
00765 
00766       /* If you are only writing one row at a time, this works */
00767       for (y = 0; y < height; y++)
00768       {
00769          png_write_rows(png_ptr, &row_pointers[y], 1);
00770       }
00771    }
00772 #endif no_entire /* use only one output method */
00773 
00774    /* You can write optional chunks like tEXt, zTXt, and tIME at the end
00775     * as well.  Shouldn't be necessary in 1.1.0 and up as all the public
00776     * chunks are supported and you can use png_set_unknown_chunks() to
00777     * register unknown chunks into the info structure to be written out.
00778     */
00779 
00780    /* It is REQUIRED to call this to finish writing the rest of the file */
00781    png_write_end(png_ptr, info_ptr);
00782 #endif hilevel
00783 
00784    /* If you png_malloced a palette, free it here (don't free info_ptr->palette,
00785       as recommended in versions 1.0.5m and earlier of this example; if
00786       libpng mallocs info_ptr->palette, libpng will free it).  If you
00787       allocated it with malloc() instead of png_malloc(), use free() instead
00788       of png_free(). */
00789    png_free(png_ptr, palette);
00790    palette=NULL;
00791 
00792    /* Similarly, if you png_malloced any data that you passed in with
00793       png_set_something(), such as a hist or trans array, free it here,
00794       when you can be sure that libpng is through with it. */
00795    png_free(png_ptr, trans);
00796    trans=NULL;
00797 
00798    /* clean up after the write, and free any memory allocated */
00799    png_destroy_write_struct(&png_ptr, &info_ptr);
00800 
00801    /* close the file */
00802    fclose(fp);
00803 
00804    /* that's it */
00805    return (OK);
00806 }
00807 
00808 #endif /* if 0 */