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src/Source/LibPNG/example.c  view on Meta::CPAN

    * background (not recommended).
    */
   png_set_strip_alpha(png_ptr);

   /* Extract multiple pixels with bit depths of 1, 2, and 4 from a single
    * byte into separate bytes (useful for paletted and grayscale images).
    */
   png_set_packing(png_ptr);

   /* Change the order of packed pixels to least significant bit first
    * (not useful if you are using png_set_packing). */
   png_set_packswap(png_ptr);

   /* Expand paletted colors into true RGB triplets */
   if (color_type == PNG_COLOR_TYPE_PALETTE)
      png_set_palette_to_rgb(png_ptr);

   /* Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */
   if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
      png_set_expand_gray_1_2_4_to_8(png_ptr);

   /* Expand paletted or RGB images with transparency to full alpha channels
    * so the data will be available as RGBA quartets.
    */
   if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS) != 0)
      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) != 0)
      png_set_background(png_ptr, image_background,
                         PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
   else
      png_set_background(png_ptr, &my_background,
                         PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);

   /* Some suggestions as to how to get a screen gamma value
    *
    * Note that screen gamma is the display_exponent, which includes
    * the CRT_exponent and any correction for viewing conditions
    */
   if (/* We have a user-defined screen gamma value */)
   {
      screen_gamma = user-defined screen_gamma;
   }
   /* This is one way that applications share the same screen gamma value */
   else if ((gamma_str = getenv("SCREEN_GAMMA")) != NULL)
   {
      screen_gamma = atof(gamma_str);
   }
   /* If we don't have another value */
   else
   {
      screen_gamma = PNG_DEFAULT_sRGB;  /* A good guess for a PC monitor
                                           in a dimly lit room */
      screen_gamma = PNG_GAMMA_MAC_18 or 1.0; /* Good guesses for Mac systems */
   }

   /* Tell libpng to handle the gamma conversion for you.  The final call
    * is a good guess for PC generated images, but it should be configurable
    * by the user at run time by the user.  It is strongly suggested that
    * your application support gamma correction.
    */

   int intent;

   if (png_get_sRGB(png_ptr, info_ptr, &intent) != 0)
      png_set_gamma(png_ptr, screen_gamma, PNG_DEFAULT_sRGB);
   else
   {
      double image_gamma;
      if (png_get_gAMA(png_ptr, info_ptr, &image_gamma) != 0)
         png_set_gamma(png_ptr, screen_gamma, image_gamma);
      else
         png_set_gamma(png_ptr, screen_gamma, 0.45455);
   }

#ifdef PNG_READ_QUANTIZE_SUPPORTED
   /* Quantize RGB files down to 8 bit palette or reduce palettes
    * to the number of colors available on your screen.
    */
   if ((color_type & PNG_COLOR_MASK_COLOR) != 0)
   {
      int num_palette;
      png_colorp palette;

      /* This reduces the image to the application supplied palette */
      if (/* We have our own palette */)
      {
         /* An array of colors to which the image should be quantized */
         png_color std_color_cube[MAX_SCREEN_COLORS];

         png_set_quantize(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
            MAX_SCREEN_COLORS, NULL, 0);
      }
      /* This reduces the image to the palette supplied in the file */
      else if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette) != 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 */
   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) != 0)
   {
      png_color_8p sig_bit_p;

      png_get_sBIT(png_ptr, info_ptr, &sig_bit_p);

src/Source/LibPNG/example.c  view on Meta::CPAN

   /* Set up the output control if you are using standard C streams */
   png_init_io(png_ptr, fp);

#else no_streams /* I/O initialization method 2 */
   /* If you are using replacement write functions, instead of calling
    * png_init_io() here you would call
    */
   png_set_write_fn(png_ptr, (void *)user_io_ptr, user_write_fn,
      user_IO_flush_function);
   /* where user_io_ptr is a structure you want available to the callbacks */
#endif no_streams /* Only use one initialization method */

#ifdef hilevel
   /* This is the easy way.  Use it if you already have all the
    * image info living in the structure.  You could "|" many
    * PNG_TRANSFORM flags into the png_transforms integer here.
    */
   png_write_png(png_ptr, info_ptr, png_transforms, NULL);

#else
   /* This is the hard way */

   /* Set the image information here.  Width and height are up to 2^31,
    * bit_depth is one of 1, 2, 4, 8, or 16, but valid values also depend on
    * the color_type selected. color_type is one of PNG_COLOR_TYPE_GRAY,
    * PNG_COLOR_TYPE_GRAY_ALPHA, PNG_COLOR_TYPE_PALETTE, PNG_COLOR_TYPE_RGB,
    * or PNG_COLOR_TYPE_RGB_ALPHA.  interlace is either PNG_INTERLACE_NONE or
    * PNG_INTERLACE_ADAM7, and the compression_type and filter_type MUST
    * currently be PNG_COMPRESSION_TYPE_BASE and PNG_FILTER_TYPE_BASE. REQUIRED
    */
   png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, PNG_COLOR_TYPE_???,
      PNG_INTERLACE_????, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);

   /* Set the palette if there is one.  REQUIRED for indexed-color images */
   palette = (png_colorp)png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH
             * (sizeof (png_color)));
   /* ... Set palette colors ... */
   png_set_PLTE(png_ptr, info_ptr, palette, PNG_MAX_PALETTE_LENGTH);
   /* You must not free palette here, because png_set_PLTE only makes a link to
    * the palette that you malloced.  Wait until you are about to destroy
    * the png structure.
    */

   /* Optional significant bit (sBIT) chunk */
   png_color_8 sig_bit;

   /* If we are dealing with a grayscale image then */
   sig_bit.gray = true_bit_depth;

   /* Otherwise, if we are dealing with a color image then */
   sig_bit.red = true_red_bit_depth;
   sig_bit.green = true_green_bit_depth;
   sig_bit.blue = true_blue_bit_depth;

   /* If the image has an alpha channel then */
   sig_bit.alpha = true_alpha_bit_depth;

   png_set_sBIT(png_ptr, info_ptr, &sig_bit);


   /* Optional gamma chunk is strongly suggested if you have any guess
    * as to the correct gamma of the image.
    */
   png_set_gAMA(png_ptr, info_ptr, gamma);

   /* Optionally write comments into the image */
   {
      png_text text_ptr[3];

      char key0[]="Title";
      char text0[]="Mona Lisa";
      text_ptr[0].key = key0;
      text_ptr[0].text = text0;
      text_ptr[0].compression = PNG_TEXT_COMPRESSION_NONE;
      text_ptr[0].itxt_length = 0;
      text_ptr[0].lang = NULL;
      text_ptr[0].lang_key = NULL;

      char key1[]="Author";
      char text1[]="Leonardo DaVinci";
      text_ptr[1].key = key1;
      text_ptr[1].text = text1;
      text_ptr[1].compression = PNG_TEXT_COMPRESSION_NONE;
      text_ptr[1].itxt_length = 0;
      text_ptr[1].lang = NULL;
      text_ptr[1].lang_key = NULL;

      char key2[]="Description";
      char text2[]="<long text>";
      text_ptr[2].key = key2;
      text_ptr[2].text = text2;
      text_ptr[2].compression = PNG_TEXT_COMPRESSION_zTXt;
      text_ptr[2].itxt_length = 0;
      text_ptr[2].lang = NULL;
      text_ptr[2].lang_key = NULL;

      png_set_text(write_ptr, write_info_ptr, text_ptr, 3);
   }

   /* Other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs */

   /* Note that if sRGB is present the gAMA and cHRM chunks must be ignored
    * on read and, if your application chooses to write them, they must
    * be written in accordance with the sRGB profile
    */

   /* Write the file header information.  REQUIRED */
   png_write_info(png_ptr, info_ptr);

   /* If you want, you can write the info in two steps, in case you need to
    * write your private chunk ahead of PLTE:
    *
    *   png_write_info_before_PLTE(write_ptr, write_info_ptr);
    *   write_my_chunk();
    *   png_write_info(png_ptr, info_ptr);
    *
    * However, given the level of known- and unknown-chunk support in 1.2.0
    * and up, this should no longer be necessary.
    */

   /* Once we write out the header, the compression type on the text