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 using namespace std;
   7
   8 namespace {
   9
  10 struct ErrorInfo
  11 {
  12         string msg;
  13 };
  14
  15 void read(png_struct *png, png_byte *data, png_size_t size)
  16 {
  17         Msp::IO::Base *in = reinterpret_cast<Msp::IO::Base *>(png_get_io_ptr(png));
  18         in->read(reinterpret_cast<char *>(data), size);
  19 }
  20
  21 void error(png_struct *png, const char *msg)
  22 {
  23         ErrorInfo *error_info = reinterpret_cast<ErrorInfo *>(png_get_error_ptr(png));
  24         error_info->msg = msg;
  25         longjmp(png_jmpbuf(png), 1);
  26 }
  27
  28 }
  29
  30
  31 namespace Msp {
  32 namespace Graphics {
  33
  34 bool is_png(const char *buf, unsigned len)
  35 {
  36         return !png_sig_cmp(reinterpret_cast<png_byte *>(const_cast<char*>(buf)), 0, len);
  37 }
  38
  39 void load_png(IO::Base &in, Image::Private &priv, const char *, unsigned sig_len)
  40 {
  41         png_struct *png = 0;
  42         png_info *info = 0;
  43         priv.data = 0;
  44
  45         try
  46         {
  47                 ErrorInfo error_info;
  48                 png = png_create_read_struct(PNG_LIBPNG_VER_STRING, &error_info, error, 0);
  49                 info = png_create_info_struct(png);
  50
  51                 if(setjmp(png_jmpbuf(png)))
  52                         throw bad_image_data(error_info.msg);
  53
  54                 png_set_read_fn(png, &in, read);
  55                 png_set_sig_bytes(png, sig_len);
  56                 png_read_info(png, info);
  57                 png_uint_32 width;
  58                 png_uint_32 height;
  59                 int depth;
  60                 int color;
  61                 png_get_IHDR(png, info, &width, &height, &depth, &color, 0, 0, 0);
  62                 priv.width = width;
  63                 priv.height = height;
  64                 if(depth!=8)
  65                         throw unsupported_image_format("depth!=8");
  66                 switch(color)
  67                 {
  68                 case PNG_COLOR_TYPE_PALETTE:    priv.fmt = COLOR_INDEX; break;
  69                 case PNG_COLOR_TYPE_GRAY:       priv.fmt = LUMINANCE; break;
  70                 case PNG_COLOR_TYPE_GRAY_ALPHA: priv.fmt = LUMINANCE_ALPHA; break;
  71                 case PNG_COLOR_TYPE_RGB:        priv.fmt = RGB; break;
  72                 case PNG_COLOR_TYPE_RGB_ALPHA:  priv.fmt = RGBA; break;
  73                 default: throw unsupported_image_format("unknown color type");
  74                 }
  75
  76                 unsigned nchans = png_get_channels(png, info);
  77                 if(nchans==4 && priv.fmt==RGB)
  78                         png_set_strip_alpha(png);
  79
  80                 unsigned rowstride = priv.width*nchans;
  81                 priv.data = new char[rowstride*priv.height];
  82                 for(unsigned y=0; y<priv.height; ++y)
  83                         png_read_row(png, reinterpret_cast<png_byte *>(priv.data+rowstride*(priv.height-1-y)), 0);
  84
  85                 png_read_end(png, 0);
  86                 png_destroy_read_struct(&png, &info, 0);
  87         }
  88         catch(...)
  89         {
  90                 png_destroy_read_struct(&png, &info, 0);
  91                 delete[] priv.data;
  92                 throw;
  93         }
  94 }
  95
  96 } // namespace Graphics
  97 } // namespace Msp
  98 #endif