/src/freeimage-svn/FreeImage/trunk/Source/FreeImage/PluginPNG.cpp

Source
// ==========================================================
// PNG Loader and Writer
//
// Design and implementation by
// - Floris van den Berg (flvdberg@wxs.nl)
// - Herve Drolon (drolon@infonie.fr)
// - Detlev Vendt (detlev.vendt@brillit.de)
// - Aaron Shumate (trek@startreker.com)
// - Tanner Helland (tannerhelland@users.sf.net)
//
// This file is part of FreeImage 3
//
// COVERED CODE IS PROVIDED UNDER THIS LICENSE ON AN "AS IS" BASIS, WITHOUT WARRANTY
// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES
// THAT THE COVERED CODE IS FREE OF DEFECTS, MERCHANTABLE, FIT FOR A PARTICULAR PURPOSE
// OR NON-INFRINGING. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE COVERED
// CODE IS WITH YOU. SHOULD ANY COVERED CODE PROVE DEFECTIVE IN ANY RESPECT, YOU (NOT
// THE INITIAL DEVELOPER OR ANY OTHER CONTRIBUTOR) ASSUME THE COST OF ANY NECESSARY
// SERVICING, REPAIR OR CORRECTION. THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL
// PART OF THIS LICENSE. NO USE OF ANY COVERED CODE IS AUTHORIZED HEREUNDER EXCEPT UNDER
// THIS DISCLAIMER.
//
// Use at your own risk!
// ==========================================================

#ifdef _MSC_VER 
#pragma warning (disable : 4786) // identifier was truncated to 'number' characters
#endif

#include "FreeImage.h"
#include "Utilities.h"

#include "../Metadata/FreeImageTag.h"

// ----------------------------------------------------------

#define PNG_BYTES_TO_CHECK 8

#undef PNG_Z_DEFAULT_COMPRESSION  // already used in ../LibPNG/pnglibconf.h

// ----------------------------------------------------------

#include "../ZLib/zlib.h"
#include "../LibPNG/png.h"

// ----------------------------------------------------------

typedef struct {
    FreeImageIO *s_io;
    fi_handle    s_handle;
} fi_ioStructure, *pfi_ioStructure;

// ==========================================================
// Plugin Interface
// ==========================================================

static int s_format_id;

// ==========================================================
// libpng interface
// ==========================================================

static void
_ReadProc(png_structp png_ptr, unsigned char *data, png_size_t size) {
    pfi_ioStructure pfio = (pfi_ioStructure)png_get_io_ptr(png_ptr);
  unsigned n = pfio->s_io->read_proc(data, (unsigned int)size, 1, pfio->s_handle);
  if(size && (n == 0)) {
    throw "Read error: invalid or corrupted PNG file";
  }
}

static void
_WriteProc(png_structp png_ptr, unsigned char *data, png_size_t size) {
    pfi_ioStructure pfio = (pfi_ioStructure)png_get_io_ptr(png_ptr);
    pfio->s_io->write_proc(data, (unsigned int)size, 1, pfio->s_handle);
}

static void
_FlushProc(png_structp png_ptr) {
  (png_structp)png_ptr;
  // empty flush implementation
}

static void
error_handler(png_structp png_ptr, const char *error) {
  FreeImage_OutputMessageProc(s_format_id, error);
  png_longjmp(png_ptr, 1);
}

// in FreeImage warnings disabled

static void
warning_handler(png_structp png_ptr, const char *warning) {
  (png_structp)png_ptr;
  (char*)warning;
}

// ==========================================================
// Metadata routines
// ==========================================================

static BOOL 
ReadMetadata(png_structp png_ptr, png_infop info_ptr, FIBITMAP *dib) {
  // XMP keyword
  const char *g_png_xmp_keyword = "XML:com.adobe.xmp";

  FITAG *tag = NULL;
  png_textp text_ptr = NULL;
  png_timep mod_time = NULL;
  int num_text = 0;

  // iTXt/tEXt/zTXt chuncks
  if(png_get_text(png_ptr, info_ptr, &text_ptr, &num_text) > 0) {
    for(int i = 0; i < num_text; i++) {
      // create a tag
      tag = FreeImage_CreateTag();
      if(!tag) return FALSE;

      DWORD tag_length = (DWORD) MAX(text_ptr[i].text_length, text_ptr[i].itxt_length);

      FreeImage_SetTagLength(tag, tag_length);
      FreeImage_SetTagCount(tag, tag_length);
      FreeImage_SetTagType(tag, FIDT_ASCII);
      FreeImage_SetTagValue(tag, text_ptr[i].text);

      if(strcmp(text_ptr[i].key, g_png_xmp_keyword) == 0) {
        // store the tag as XMP
        FreeImage_SetTagKey(tag, g_TagLib_XMPFieldName);
        FreeImage_SetMetadata(FIMD_XMP, dib, FreeImage_GetTagKey(tag), tag);
      } else {
        // store the tag as a comment
        FreeImage_SetTagKey(tag, text_ptr[i].key);
        FreeImage_SetMetadata(FIMD_COMMENTS, dib, FreeImage_GetTagKey(tag), tag);
      }
      
      // destroy the tag
      FreeImage_DeleteTag(tag);
    }
  }

  // timestamp chunk
  if(png_get_tIME(png_ptr, info_ptr, &mod_time)) {
    char timestamp[32];
    // create a tag
    tag = FreeImage_CreateTag();
    if(!tag) return FALSE;

    // convert as 'yyyy:MM:dd hh:mm:ss'
    sprintf(timestamp, "%4d:%02d:%02d %2d:%02d:%02d", mod_time->year, mod_time->month, mod_time->day, mod_time->hour, mod_time->minute, mod_time->second);

    DWORD tag_length = (DWORD)strlen(timestamp) + 1;
    FreeImage_SetTagLength(tag, tag_length);
    FreeImage_SetTagCount(tag, tag_length);
    FreeImage_SetTagType(tag, FIDT_ASCII);
    FreeImage_SetTagID(tag, TAG_DATETIME);
    FreeImage_SetTagValue(tag, timestamp);

    // store the tag as Exif-TIFF
    FreeImage_SetTagKey(tag, "DateTime");
    FreeImage_SetMetadata(FIMD_EXIF_MAIN, dib, FreeImage_GetTagKey(tag), tag);

    // destroy the tag
    FreeImage_DeleteTag(tag);
  }

  return TRUE;
}

static BOOL 
WriteMetadata(png_structp png_ptr, png_infop info_ptr, FIBITMAP *dib) {
  // XMP keyword
  const char *g_png_xmp_keyword = "XML:com.adobe.xmp";

  FITAG *tag = NULL;
  FIMETADATA *mdhandle = NULL;
  BOOL bResult = TRUE;

  png_text text_metadata;
  png_time mod_time;

  // set the 'Comments' metadata as iTXt chuncks

  mdhandle = FreeImage_FindFirstMetadata(FIMD_COMMENTS, dib, &tag);

  if(mdhandle) {
    do {
      memset(&text_metadata, 0, sizeof(png_text));
      text_metadata.compression = 1;              // iTXt, none
      text_metadata.key = (char*)FreeImage_GetTagKey(tag);  // keyword, 1-79 character description of "text"
      text_metadata.text = (char*)FreeImage_GetTagValue(tag); // comment, may be an empty string (ie "")
      text_metadata.text_length = FreeImage_GetTagLength(tag);// length of the text string
      text_metadata.itxt_length = FreeImage_GetTagLength(tag);// length of the itxt string
      text_metadata.lang = 0;    // language code, 0-79 characters or a NULL pointer
      text_metadata.lang_key = 0;  // keyword translated UTF-8 string, 0 or more chars or a NULL pointer

      // set the tag 
      png_set_text(png_ptr, info_ptr, &text_metadata, 1);

    } while(FreeImage_FindNextMetadata(mdhandle, &tag));

    FreeImage_FindCloseMetadata(mdhandle);
    bResult &= TRUE;
  }

  // set the 'XMP' metadata as iTXt chuncks
  tag = NULL;
  FreeImage_GetMetadata(FIMD_XMP, dib, g_TagLib_XMPFieldName, &tag);
  if(tag && FreeImage_GetTagLength(tag)) {
    memset(&text_metadata, 0, sizeof(png_text));
    text_metadata.compression = 1;              // iTXt, none
    text_metadata.key = (char*)g_png_xmp_keyword;     // keyword, 1-79 character description of "text"
    text_metadata.text = (char*)FreeImage_GetTagValue(tag); // comment, may be an empty string (ie "")
    text_metadata.text_length = FreeImage_GetTagLength(tag);// length of the text string
    text_metadata.itxt_length = FreeImage_GetTagLength(tag);// length of the itxt string
    text_metadata.lang = 0;    // language code, 0-79 characters or a NULL pointer
    text_metadata.lang_key = 0;  // keyword translated UTF-8 string, 0 or more chars or a NULL pointer

    // set the tag 
    png_set_text(png_ptr, info_ptr, &text_metadata, 1);
    bResult &= TRUE;
  }

  // set the Exif-TIFF 'DateTime' metadata as a tIME chunk
  tag = NULL;
  FreeImage_GetMetadata(FIMD_EXIF_MAIN, dib, "DateTime", &tag);
  if(tag && FreeImage_GetTagLength(tag)) {
    int year, month, day, hour, minute, second;
    const char *value = (char*)FreeImage_GetTagValue(tag);
    if(sscanf(value, "%4d:%02d:%02d %2d:%02d:%02d", &year, &month, &day, &hour, &minute, &second) == 6) {
      mod_time.year = (png_uint_16)year;
      mod_time.month  = (png_byte)month;
      mod_time.day  = (png_byte)day;
      mod_time.hour = (png_byte)hour;
      mod_time.minute = (png_byte)minute;
      mod_time.second = (png_byte)second;
      png_set_tIME (png_ptr, info_ptr, &mod_time);
    }
  }

  return bResult;
}

// ==========================================================
// Plugin Implementation
// ==========================================================

static const char * DLL_CALLCONV
Format() {
  return "PNG";
}

static const char * DLL_CALLCONV
Description() {
  return "Portable Network Graphics";
}

static const char * DLL_CALLCONV
Extension() {
  return "png";
}

static const char * DLL_CALLCONV
RegExpr() {
  return "^.PNG\r";
}

static const char * DLL_CALLCONV
MimeType() {
  return "image/png";
}

static BOOL DLL_CALLCONV
Validate(FreeImageIO *io, fi_handle handle) {
  BYTE png_signature[8] = { 137, 80, 78, 71, 13, 10, 26, 10 };
  BYTE signature[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };

  io->read_proc(&signature, 1, 8, handle);

  return (memcmp(png_signature, signature, 8) == 0);
}

static BOOL DLL_CALLCONV
SupportsExportDepth(int depth) {
  return (
      (depth == 1) ||
      (depth == 4) ||
      (depth == 8) ||
      (depth == 24) ||
      (depth == 32)
    );
}

static BOOL DLL_CALLCONV 
SupportsExportType(FREE_IMAGE_TYPE type) {
  return (
    (type == FIT_BITMAP) ||
    (type == FIT_UINT16) ||
    (type == FIT_RGB16) ||
    (type == FIT_RGBA16)
  );
}

static BOOL DLL_CALLCONV
SupportsICCProfiles() {
  return TRUE;
}

static BOOL DLL_CALLCONV
SupportsNoPixels() {
  return TRUE;
}

// --------------------------------------------------------------------------

/**
Configure the decoder so that decoded pixels are compatible with a FREE_IMAGE_TYPE format. 
Set conversion instructions as needed. 
@param png_ptr PNG handle
@param info_ptr PNG info handle
@param flags Decoder flags
@param output_image_type Returned FreeImage converted image type
@return Returns TRUE if successful, returns FALSE otherwise
@see png_read_update_info
*/
static BOOL 
ConfigureDecoder(png_structp png_ptr, png_infop info_ptr, int flags, FREE_IMAGE_TYPE *output_image_type) {
  // get original image info
  const int color_type = png_get_color_type(png_ptr, info_ptr);
  const int bit_depth = png_get_bit_depth(png_ptr, info_ptr);
  const int pixel_depth = bit_depth * png_get_channels(png_ptr, info_ptr);

  FREE_IMAGE_TYPE image_type = FIT_BITMAP;  // assume standard image type

  // check for transparency table or single transparent color
  BOOL bIsTransparent = png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS) == PNG_INFO_tRNS ? TRUE : FALSE;

  // check allowed combinations of colour type and bit depth
  // then get converted FreeImage type

  switch(color_type) {
    case PNG_COLOR_TYPE_GRAY:   // color type '0', bitdepth = 1, 2, 4, 8, 16
      switch(bit_depth) {
        case 1:
        case 2:
        case 4:
        case 8:
          // expand grayscale images to the full 8-bit from 2-bit/pixel
          if (pixel_depth == 2) {
            png_set_expand_gray_1_2_4_to_8(png_ptr);
          }

          // if a tRNS chunk is provided, we must also expand the grayscale data to 8-bits,
          // this allows us to make use of the transparency table with existing FreeImage methods
          if (bIsTransparent && (pixel_depth < 8)) {
            png_set_expand_gray_1_2_4_to_8(png_ptr);
          }
          break;

        case 16:
          image_type = (pixel_depth == 16) ? FIT_UINT16 : FIT_UNKNOWN;

          // 16-bit grayscale images can contain a transparent value (shade)
          // if found, expand the transparent value to a full alpha channel
          if (bIsTransparent && (image_type != FIT_UNKNOWN)) {
            // expand tRNS to a full alpha channel
            png_set_tRNS_to_alpha(png_ptr);
            
            // expand new 16-bit gray + 16-bit alpha to full 64-bit RGBA
            png_set_gray_to_rgb(png_ptr);

            image_type = FIT_RGBA16;
          }
          break;

        default:
          image_type = FIT_UNKNOWN;
          break;
      }
      break;

    case PNG_COLOR_TYPE_RGB:   // color type '2', bitdepth = 8, 16
      switch(bit_depth) {
        case 8:
          image_type = (pixel_depth == 24) ? FIT_BITMAP : FIT_UNKNOWN;
          break;
        case 16:
          image_type = (pixel_depth == 48) ? FIT_RGB16 : FIT_UNKNOWN;
          break;
        default:
          image_type = FIT_UNKNOWN;
          break;
      }
      // sometimes, 24- or 48-bit images may contain transparency information
      // check for this use case and convert to an alpha-compatible format
      if (bIsTransparent && (image_type != FIT_UNKNOWN)) {
        // if the image is 24-bit RGB, mark it as 32-bit; if it is 48-bit, mark it as 64-bit
        image_type = (pixel_depth == 24) ? FIT_BITMAP : (pixel_depth == 48) ? FIT_RGBA16 : FIT_UNKNOWN;
        // expand tRNS chunk to alpha channel
        png_set_tRNS_to_alpha(png_ptr);
      }
      break;

    case PNG_COLOR_TYPE_PALETTE: // color type '3', bitdepth = 1, 2, 4, 8
      switch(bit_depth) {
        case 1:
        case 2:
        case 4:
        case 8:
          // expand palette images to the full 8 bits from 2 bits/pixel
          if (pixel_depth == 2) {
            png_set_packing(png_ptr);
          }

          // if a tRNS chunk is provided, we must also expand the palletized data to 8-bits,
          // this allows us to make use of the transparency table with existing FreeImage methods
          if (bIsTransparent && (pixel_depth < 8)) {
            png_set_packing(png_ptr);
          }
          break;

        default:
          image_type = FIT_UNKNOWN;
          break;
      }
      break;

    case PNG_COLOR_TYPE_GRAY_ALPHA: // color type '4', bitdepth = 8, 16
      switch(bit_depth) {
        case 8:
          // 8-bit grayscale + 8-bit alpha => convert to 32-bit RGBA
          image_type = (pixel_depth == 16) ? FIT_BITMAP : FIT_UNKNOWN;
          break;
        case 16:
          // 16-bit grayscale + 16-bit alpha => convert to 64-bit RGBA
          image_type = (pixel_depth == 32) ? FIT_RGBA16 : FIT_UNKNOWN;
          break;
        default:
          image_type = FIT_UNKNOWN;
          break;
      }
      // expand 8-bit greyscale + 8-bit alpha to 32-bit
      // expand 16-bit greyscale + 16-bit alpha to 64-bit
      png_set_gray_to_rgb(png_ptr);
      break;

    case PNG_COLOR_TYPE_RGB_ALPHA: // color type '6', bitdepth = 8, 16
      switch(bit_depth) {
        case 8:
          break;
        case 16:
          image_type = (pixel_depth == 64) ? FIT_RGBA16 : FIT_UNKNOWN;
          break;
        default:
          image_type = FIT_UNKNOWN;
          break;
      }
      break;
  }

  // check for unknown or invalid formats
  if(image_type == FIT_UNKNOWN) {
    *output_image_type = image_type;
    return FALSE;
  }

#ifndef FREEIMAGE_BIGENDIAN
  if((image_type == FIT_UINT16) || (image_type == FIT_RGB16) || (image_type == FIT_RGBA16)) {
    // turn on 16-bit byte swapping
    png_set_swap(png_ptr);
  }
#endif            

#if FREEIMAGE_COLORORDER == FREEIMAGE_COLORORDER_BGR
  if((image_type == FIT_BITMAP) && ((color_type == PNG_COLOR_TYPE_RGB) || (color_type == PNG_COLOR_TYPE_RGB_ALPHA))) {
    // flip the RGB pixels to BGR (or RGBA to BGRA)
    png_set_bgr(png_ptr);
  }
#endif

  // gamma correction
  // unlike the example in the libpng documentation, we have *no* idea where
  // this file may have come from--so if it doesn't have a file gamma, don't
  // do any correction ("do no harm")

  if (png_get_valid(png_ptr, info_ptr, PNG_INFO_gAMA)) {
    double gamma = 0;
    double screen_gamma = 2.2;

    if (png_get_gAMA(png_ptr, info_ptr, &gamma) && ( flags & PNG_IGNOREGAMMA ) != PNG_IGNOREGAMMA) {
      png_set_gamma(png_ptr, screen_gamma, gamma);
    }
  }

  // all transformations have been registered; now update info_ptr data   
  png_read_update_info(png_ptr, info_ptr);

  // return the output image type
  *output_image_type = image_type;

  return TRUE;
}

static FIBITMAP * DLL_CALLCONV
Load(FreeImageIO *io, fi_handle handle, int page, int flags, void *data) {
  png_structp png_ptr = NULL;
  png_infop info_ptr = NULL;
  png_uint_32 width, height;
  int color_type;
  int bit_depth;
  int pixel_depth = 0;  // pixel_depth = bit_depth * channels

  FIBITMAP *dib = NULL;
  png_bytepp row_pointers = NULL;

    fi_ioStructure fio;
    fio.s_handle = handle;
  fio.s_io = io;
    
  if (handle) {
    BOOL header_only = (flags & FIF_LOAD_NOPIXELS) == FIF_LOAD_NOPIXELS;

    try {   
      // check to see if the file is in fact a PNG file

      BYTE png_check[PNG_BYTES_TO_CHECK];

      io->read_proc(png_check, PNG_BYTES_TO_CHECK, 1, handle);

      if (png_sig_cmp(png_check, (png_size_t)0, PNG_BYTES_TO_CHECK) != 0) {
        return NULL; // Bad signature
      }
      
      // create the chunk manage structure

      png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, (png_voidp)NULL, error_handler, warning_handler);

      if (!png_ptr) {
        return NULL;     
      }

      // create the info structure

        info_ptr = png_create_info_struct(png_ptr);

      if (!info_ptr) {
        png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
        return NULL;
      }

      // init the IO

      png_set_read_fn(png_ptr, &fio, _ReadProc);            
      
      // PNG errors will be redirected here

      if (setjmp(png_jmpbuf(png_ptr))) {
        // assume error_handler was called before by the PNG library
        throw((const char*)NULL);
      }

      // because we have already read the signature...

      png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK);

      // read the IHDR chunk

      png_read_info(png_ptr, info_ptr);
      png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, NULL, NULL, NULL);

      // configure the decoder

      FREE_IMAGE_TYPE image_type = FIT_BITMAP;

      if(!ConfigureDecoder(png_ptr, info_ptr, flags, &image_type)) {
        throw FI_MSG_ERROR_UNSUPPORTED_FORMAT;
      }

      // update image info

      color_type = png_get_color_type(png_ptr, info_ptr);
      bit_depth = png_get_bit_depth(png_ptr, info_ptr);
      pixel_depth = bit_depth * png_get_channels(png_ptr, info_ptr);

      // create a dib and write the bitmap header
      // set up the dib palette, if needed

      switch (color_type) {
        case PNG_COLOR_TYPE_RGB:
        case PNG_COLOR_TYPE_RGB_ALPHA:
          dib = FreeImage_AllocateHeaderT(header_only, image_type, width, height, pixel_depth, FI_RGBA_RED_MASK, FI_RGBA_GREEN_MASK, FI_RGBA_BLUE_MASK);
          break;

        case PNG_COLOR_TYPE_PALETTE:
          dib = FreeImage_AllocateHeaderT(header_only, image_type, width, height, pixel_depth, FI_RGBA_RED_MASK, FI_RGBA_GREEN_MASK, FI_RGBA_BLUE_MASK);
          if(dib) {
            png_colorp png_palette = NULL;
            int palette_entries = 0;

            png_get_PLTE(png_ptr,info_ptr, &png_palette, &palette_entries);

            palette_entries = MIN((unsigned)palette_entries, FreeImage_GetColorsUsed(dib));

            // store the palette

            RGBQUAD *palette = FreeImage_GetPalette(dib);
            for(int i = 0; i < palette_entries; i++) {
              palette[i].rgbRed   = png_palette[i].red;
              palette[i].rgbGreen = png_palette[i].green;
              palette[i].rgbBlue  = png_palette[i].blue;
            }
          }
          break;

        case PNG_COLOR_TYPE_GRAY:
          dib = FreeImage_AllocateHeaderT(header_only, image_type, width, height, pixel_depth, FI_RGBA_RED_MASK, FI_RGBA_GREEN_MASK, FI_RGBA_BLUE_MASK);

          if(dib && (pixel_depth <= 8)) {
            RGBQUAD *palette = FreeImage_GetPalette(dib);
            const int palette_entries = 1 << pixel_depth;

            for(int i = 0; i < palette_entries; i++) {
              palette[i].rgbRed   =
              palette[i].rgbGreen =
              palette[i].rgbBlue  = (BYTE)((i * 255) / (palette_entries - 1));
            }
          }
          break;

        default:
          throw FI_MSG_ERROR_UNSUPPORTED_FORMAT;
      }

      if(!dib) {
        throw FI_MSG_ERROR_DIB_MEMORY;
      }

      // store the transparency table

      if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
        // array of alpha (transparency) entries for palette
        png_bytep trans_alpha = NULL;
        // number of transparent entries
        int num_trans = 0;            
        // graylevel or color sample values of the single transparent color for non-paletted images
        png_color_16p trans_color = NULL;

        png_get_tRNS(png_ptr, info_ptr, &trans_alpha, &num_trans, &trans_color);

        if((color_type == PNG_COLOR_TYPE_GRAY) && trans_color) {
          // single transparent color
          if (trans_color->gray < 256) { 
            BYTE table[256]; 
            memset(table, 0xFF, 256); 
            table[trans_color->gray] = 0; 
            FreeImage_SetTransparencyTable(dib, table, 256); 
          }
          // check for a full transparency table, too
          else if ((trans_alpha) && (pixel_depth <= 8)) {
            FreeImage_SetTransparencyTable(dib, (BYTE *)trans_alpha, num_trans);
          }

        } else if((color_type == PNG_COLOR_TYPE_PALETTE) && trans_alpha) {
          // transparency table
          FreeImage_SetTransparencyTable(dib, (BYTE *)trans_alpha, num_trans);
        }
      }

      // store the background color (only supported for FIT_BITMAP types)

      if ((image_type == FIT_BITMAP) && png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD)) {
        // Get the background color to draw transparent and alpha images over.
        // 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_16p image_background = NULL;
        RGBQUAD rgbBkColor;

        if (png_get_bKGD(png_ptr, info_ptr, &image_background)) {
          rgbBkColor.rgbRed      = (BYTE)image_background->red;
          rgbBkColor.rgbGreen    = (BYTE)image_background->green;
          rgbBkColor.rgbBlue     = (BYTE)image_background->blue;
          rgbBkColor.rgbReserved = 0;

          FreeImage_SetBackgroundColor(dib, &rgbBkColor);
        }
      }

      // get physical resolution

      if (png_get_valid(png_ptr, info_ptr, PNG_INFO_pHYs)) {
        png_uint_32 res_x, res_y;
        
        // we'll overload this var and use 0 to mean no phys data,
        // since if it's not in meters we can't use it anyway

        int res_unit_type = PNG_RESOLUTION_UNKNOWN;

        png_get_pHYs(png_ptr,info_ptr, &res_x, &res_y, &res_unit_type);

        if (res_unit_type == PNG_RESOLUTION_METER) {
          FreeImage_SetDotsPerMeterX(dib, res_x);
          FreeImage_SetDotsPerMeterY(dib, res_y);
        }
      }

      // get possible ICC profile

      if (png_get_valid(png_ptr, info_ptr, PNG_INFO_iCCP)) {
        png_charp profile_name = NULL;
        png_bytep profile_data = NULL;
        png_uint_32 profile_length = 0;
        int  compression_type;

        png_get_iCCP(png_ptr, info_ptr, &profile_name, &compression_type, &profile_data, &profile_length);

        // copy ICC profile data (must be done after FreeImage_AllocateHeader)

        FreeImage_CreateICCProfile(dib, profile_data, profile_length);
      }

      // --- header only mode => clean-up and return

      if (header_only) {
        // get possible metadata (it can be located both before and after the image data)
        ReadMetadata(png_ptr, info_ptr, dib);
        if (png_ptr) {
          // clean up after the read, and free any memory allocated - REQUIRED
          png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
        }
        return dib;
      }

      // set the individual row_pointers to point at the correct offsets

      row_pointers = (png_bytepp)malloc(height * sizeof(png_bytep));

      if (!row_pointers) {
        png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
        FreeImage_Unload(dib);
        return NULL;
      }

      // read in the bitmap bits via the pointer table
      // allow loading of PNG with minor errors (such as images with several IDAT chunks)

      for (png_uint_32 k = 0; k < height; k++) {
        row_pointers[height - 1 - k] = FreeImage_GetScanLine(dib, k);
      }

      png_set_benign_errors(png_ptr, 1);
      png_read_image(png_ptr, row_pointers);

      // check if the bitmap contains transparency, if so enable it in the header

      if (FreeImage_GetBPP(dib) == 32) {
        if (FreeImage_GetColorType(dib) == FIC_RGBALPHA) {
          FreeImage_SetTransparent(dib, TRUE);
        } else {
          FreeImage_SetTransparent(dib, FALSE);
        }
      }
        
      // cleanup

      if (row_pointers) {
        free(row_pointers);
        row_pointers = NULL;
      }

      // read the rest of the file, getting any additional chunks in info_ptr

      png_read_end(png_ptr, info_ptr);

      // get possible metadata (it can be located both before and after the image data)

      ReadMetadata(png_ptr, info_ptr, dib);

      if (png_ptr) {
        // clean up after the read, and free any memory allocated - REQUIRED
        png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
      }

      return dib;

    } catch (const char *text) {
      if (png_ptr) {
        png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
      }
      if (row_pointers) {
        free(row_pointers);
      }
      if (dib) {
        FreeImage_Unload(dib);
      }
      if (NULL != text) {
        FreeImage_OutputMessageProc(s_format_id, text);
      }
      
      return NULL;
    }
  }     

  return NULL;
}

// --------------------------------------------------------------------------

static BOOL DLL_CALLCONV
Save(FreeImageIO *io, FIBITMAP *dib, fi_handle handle, int page, int flags, void *data) {
  png_structp png_ptr;
  png_infop info_ptr;
  png_colorp palette = NULL;
  png_uint_32 width, height;
  BOOL has_alpha_channel = FALSE;

  RGBQUAD *pal;         // pointer to dib palette
  int bit_depth, pixel_depth;   // pixel_depth = bit_depth * channels
  int palette_entries;
  int interlace_type;

  fi_ioStructure fio;
    fio.s_handle = handle;
  fio.s_io = io;

  if ((dib) && (handle)) {
    try {
      // create the chunk manage structure

      png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, (png_voidp)NULL, error_handler, warning_handler);

      if (!png_ptr)  {
        return FALSE;
      }

      // allocate/initialize the image information data.

      info_ptr = png_create_info_struct(png_ptr);

      if (!info_ptr)  {
        png_destroy_write_struct(&png_ptr,  (png_infopp)NULL);
        return FALSE;
      }

      // 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

        png_destroy_write_struct(&png_ptr, &info_ptr);

        return FALSE;
      }

      // init the IO
            
      png_set_write_fn(png_ptr, &fio, _WriteProc, _FlushProc);

      // set physical resolution

      png_uint_32 res_x = (png_uint_32)FreeImage_GetDotsPerMeterX(dib);
      png_uint_32 res_y = (png_uint_32)FreeImage_GetDotsPerMeterY(dib);

      if ((res_x > 0) && (res_y > 0))  {
        png_set_pHYs(png_ptr, info_ptr, res_x, res_y, PNG_RESOLUTION_METER);
      }
  
      // 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

      width = FreeImage_GetWidth(dib);
      height = FreeImage_GetHeight(dib);
      pixel_depth = FreeImage_GetBPP(dib);

      BOOL bInterlaced = FALSE;
      if( (flags & PNG_INTERLACED) == PNG_INTERLACED) {
        interlace_type = PNG_INTERLACE_ADAM7;
        bInterlaced = TRUE;
      } else {
        interlace_type = PNG_INTERLACE_NONE;
      }

      // set the ZLIB compression level or default to PNG default compression level (ZLIB level = 6)
      int zlib_level = flags & 0x0F;
      if((zlib_level >= 1) && (zlib_level <= 9)) {
        png_set_compression_level(png_ptr, zlib_level);
      } else if((flags & PNG_Z_NO_COMPRESSION) == PNG_Z_NO_COMPRESSION) {
        png_set_compression_level(png_ptr, Z_NO_COMPRESSION);
      }

      // filtered strategy works better for high color images
      if(pixel_depth >= 16){
        png_set_compression_strategy(png_ptr, Z_FILTERED);
        png_set_filter(png_ptr, 0, PNG_FILTER_NONE|PNG_FILTER_SUB|PNG_FILTER_PAETH);
      } else {
        png_set_compression_strategy(png_ptr, Z_DEFAULT_STRATEGY);
      }

      FREE_IMAGE_TYPE image_type = FreeImage_GetImageType(dib);
      if(image_type == FIT_BITMAP) {
        // standard image type
        bit_depth = (pixel_depth > 8) ? 8 : pixel_depth;
      } else {
        // 16-bit greyscale or 16-bit RGB(A)
        bit_depth = 16;
      }

      // check for transparent images
      BOOL bIsTransparent = 
        (image_type == FIT_BITMAP) && FreeImage_IsTransparent(dib) && (FreeImage_GetTransparencyCount(dib) > 0) ? TRUE : FALSE;

      switch (FreeImage_GetColorType(dib)) {
        case FIC_MINISWHITE:
          if(!bIsTransparent) {
            // Invert monochrome files to have 0 as black and 1 as white (no break here)
            png_set_invert_mono(png_ptr);
          }
          // (fall through)

        case FIC_MINISBLACK:
          if(!bIsTransparent) {
            png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, 
              PNG_COLOR_TYPE_GRAY, interlace_type, 
              PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
            break;
          }
          // If a monochrome image is transparent, save it with a palette
          // (fall through)

        case FIC_PALETTE:
        {
          png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, 
            PNG_COLOR_TYPE_PALETTE, interlace_type, 
            PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);

          // set the palette

          palette_entries = 1 << bit_depth;
          palette = (png_colorp)png_malloc(png_ptr, palette_entries * sizeof (png_color));
          pal = FreeImage_GetPalette(dib);

          for (int i = 0; i < palette_entries; i++) {
            palette[i].red   = pal[i].rgbRed;
            palette[i].green = pal[i].rgbGreen;
            palette[i].blue  = pal[i].rgbBlue;
          }
          
          png_set_PLTE(png_ptr, info_ptr, palette, palette_entries);

          // 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.

          break;
        }

        case FIC_RGBALPHA :
          has_alpha_channel = TRUE;

          png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, 
            PNG_COLOR_TYPE_RGBA, interlace_type, 
            PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);

#if FREEIMAGE_COLORORDER == FREEIMAGE_COLORORDER_BGR
          // flip BGR pixels to RGB
          if(image_type == FIT_BITMAP) {
            png_set_bgr(png_ptr);
          }
#endif
          break;
  
        case FIC_RGB:
          png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, 
            PNG_COLOR_TYPE_RGB, interlace_type, 
            PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);

#if FREEIMAGE_COLORORDER == FREEIMAGE_COLORORDER_BGR
          // flip BGR pixels to RGB
          if(image_type == FIT_BITMAP) {
            png_set_bgr(png_ptr);
          }
#endif
          break;
          
        case FIC_CMYK:
          break;
      }

      // write possible ICC profile

      FIICCPROFILE *iccProfile = FreeImage_GetICCProfile(dib);
      if (iccProfile->size && iccProfile->data) {
        // skip ICC profile check
        png_set_option(png_ptr, PNG_SKIP_sRGB_CHECK_PROFILE, 1);
        png_set_iCCP(png_ptr, info_ptr, "Embedded Profile", 0, (png_const_bytep)iccProfile->data, iccProfile->size);
      }

      // write metadata

      WriteMetadata(png_ptr, info_ptr, dib);

      // 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);

      // set the transparency table

      if (bIsTransparent) {
        png_set_tRNS(png_ptr, info_ptr, FreeImage_GetTransparencyTable(dib), FreeImage_GetTransparencyCount(dib), NULL);
      }

      // set the background color

      if(FreeImage_HasBackgroundColor(dib)) {
        png_color_16 image_background;
        RGBQUAD rgbBkColor;

        FreeImage_GetBackgroundColor(dib, &rgbBkColor);
        memset(&image_background, 0, sizeof(png_color_16));
        image_background.blue  = rgbBkColor.rgbBlue;
        image_background.green = rgbBkColor.rgbGreen;
        image_background.red   = rgbBkColor.rgbRed;
        image_background.index = rgbBkColor.rgbReserved;

        png_set_bKGD(png_ptr, info_ptr, &image_background);
      }
      
      // Write the file header information.

      png_write_info(png_ptr, info_ptr);

      // write out the image data

#ifndef FREEIMAGE_BIGENDIAN
      if (bit_depth == 16) {
        // turn on 16 bit byte swapping
        png_set_swap(png_ptr);
      }
#endif

      int number_passes = 1;
      if (bInterlaced) {
        number_passes = png_set_interlace_handling(png_ptr);
      }

      if ((pixel_depth == 32) && (!has_alpha_channel)) {
        BYTE *buffer = (BYTE *)malloc(width * 3);

        // transparent conversion to 24-bit
        // the number of passes is either 1 for non-interlaced images, or 7 for interlaced images
        for (int pass = 0; pass < number_passes; pass++) {
          for (png_uint_32 k = 0; k < height; k++) {
            FreeImage_ConvertLine32To24(buffer, FreeImage_GetScanLine(dib, height - k - 1), width);
            png_write_row(png_ptr, buffer);
          }
        }
        free(buffer);
      } else {
        // the number of passes is either 1 for non-interlaced images, or 7 for interlaced images
        for (int pass = 0; pass < number_passes; pass++) {
          for (png_uint_32 k = 0; k < height; k++) {
            png_write_row(png_ptr, FreeImage_GetScanLine(dib, height - k - 1));
          }
        }
      }

      // It is REQUIRED to call this to finish writing the rest of the file
      // Bug with png_flush

      png_write_end(png_ptr, info_ptr);

      // clean up after the write, and free any memory allocated
      if (palette) {
        png_free(png_ptr, palette);
      }

      png_destroy_write_struct(&png_ptr, &info_ptr);

      return TRUE;

    } catch (const char *text) {
      if(png_ptr) {
        png_destroy_write_struct(&png_ptr, &info_ptr);
      }
      FreeImage_OutputMessageProc(s_format_id, text);
    }
  }

  return FALSE;
}

// ==========================================================
//   Init
// ==========================================================

void DLL_CALLCONV
InitPNG(Plugin *plugin, int format_id) {
  s_format_id = format_id;

  plugin->format_proc = Format;
  plugin->description_proc = Description;
  plugin->extension_proc = Extension;
  plugin->regexpr_proc = RegExpr;
  plugin->open_proc = NULL;
  plugin->close_proc = NULL;
  plugin->pagecount_proc = NULL;
  plugin->pagecapability_proc = NULL;
  plugin->load_proc = Load;
  plugin->save_proc = Save;
  plugin->validate_proc = Validate;
  plugin->mime_proc = MimeType;
  plugin->supports_export_bpp_proc = SupportsExportDepth;
  plugin->supports_export_type_proc = SupportsExportType;
  plugin->supports_icc_profiles_proc = SupportsICCProfiles;
  plugin->supports_no_pixels_proc = SupportsNoPixels;
}

Coverage Report

Created: 2025-12-02 06:51