source/graphics/image_png.cpp

   1 #ifdef WITH_LIBPNG
   2 #include <png.h>
   3 #include "image_png.h"
   4 #include "image_private.h"
   5
   6 namespace {
   7
   8 void read(png_struct *png, png_byte *data, png_size_t size)
   9 {
  10         Msp::IO::Base *in = reinterpret_cast<Msp::IO::Base *>(png_get_io_ptr(png));
  11         in->read(reinterpret_cast<char *>(data), size);
  12 }
  13
  14 }
  15
  16
  17 namespace Msp {
  18 namespace Graphics {
  19
  20 bool is_png(const void *buf, unsigned len)
  21 {
  22         return !png_sig_cmp(reinterpret_cast<png_byte *>(const_cast<void *>(buf)), 0, len);
  23 }
  24
  25 void load_png(IO::Base &in, Image::Private &priv)
  26 {
  27         png_struct *png = 0;
  28         png_info *info = 0;
  29         priv.data = 0;
  30
  31         try
  32         {
  33                 png = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
  34                 info = png_create_info_struct(png);
  35
  36                 if(setjmp(png_jmpbuf(png)))
  37                         throw bad_image_data("PNG error");
  38
  39                 png_set_read_fn(png, &in, read);
  40                 png_read_info(png, info);
  41                 png_uint_32 width;
  42                 png_uint_32 height;
  43                 int depth;
  44                 int color;
  45                 png_get_IHDR(png, info, &width, &height, &depth, &color, 0, 0, 0);
  46                 priv.width = width;
  47                 priv.height = height;
  48                 if(depth!=8)
  49                         throw unsupported_image_format("depth!=8");
  50                 switch(color)
  51                 {
  52                 case PNG_COLOR_TYPE_PALETTE:    priv.fmt = COLOR_INDEX; break;
  53                 case PNG_COLOR_TYPE_GRAY:       priv.fmt = LUMINANCE; break;
  54                 case PNG_COLOR_TYPE_GRAY_ALPHA: priv.fmt = LUMINANCE_ALPHA; break;
  55                 case PNG_COLOR_TYPE_RGB:        priv.fmt = RGB; break;
  56                 case PNG_COLOR_TYPE_RGB_ALPHA:  priv.fmt = RGBA; break;
  57                 default: throw unsupported_image_format("unknown color type");
  58                 }
  59
  60                 unsigned nchans = png_get_channels(png, info);
  61                 if(nchans==4 && priv.fmt==RGB)
  62                         png_set_strip_alpha(png);
  63
  64                 unsigned rowstride = priv.width*nchans;
  65                 priv.data = new char[rowstride*priv.height];
  66                 for(unsigned y=0; y<priv.height; ++y)
  67                         png_read_row(png, reinterpret_cast<png_byte *>(priv.data+rowstride*(priv.height-1-y)), 0);
  68
  69                 png_read_end(png, 0);
  70                 png_destroy_read_struct(&png, &info, 0);
  71         }
  72         catch(...)
  73         {
  74                 png_destroy_read_struct(&png, &info, 0);
  75                 delete[] priv.data;
  76                 throw;
  77         }
  78 }
  79
  80 } // namespace Graphics
  81 } // namespace Msp
  82 #endif