source/graphics/png/pngloader.cpp

   1 #include <png.h>
   2 #include "pngloader.h"
   3
   4 using namespace std;
   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 void error(png_struct *png, const char *msg)
  15 {
  16         string *message = reinterpret_cast<string *>(png_get_error_ptr(png));
  17         *message = msg;
  18         longjmp(png_jmpbuf(png), 1);
  19 }
  20
  21 } // namespace
  22
  23
  24 namespace Msp {
  25 namespace Graphics {
  26
  27 struct PngLoader::Private
  28 {
  29         std::string message;
  30         png_struct *png;
  31         png_info *info;
  32         int interlace;
  33 };
  34
  35
  36 PngLoader::PngLoader(IO::Base &io, unsigned sig_bytes):
  37         priv(new Private)
  38 {
  39         priv->png = png_create_read_struct(PNG_LIBPNG_VER_STRING, &priv->message, error, 0);
  40         priv->info = png_create_info_struct(priv->png);
  41
  42         // These probably won't give any errors
  43         png_set_read_fn(priv->png, &io, read);
  44         png_set_sig_bytes(priv->png, sig_bytes);
  45 }
  46
  47 PngLoader::~PngLoader()
  48 {
  49         png_destroy_read_struct(&priv->png, &priv->info, 0);
  50         delete priv;
  51 }
  52
  53 bool PngLoader::detect(const std::string &sig)
  54 {
  55         return !png_sig_cmp(reinterpret_cast<png_byte *>(const_cast<char*>(sig.data())), 0, sig.size());
  56 }
  57
  58 void PngLoader::load_headers_(Image::Data &data)
  59 {
  60         if(setjmp(png_jmpbuf(priv->png)))
  61         {
  62                 throw bad_image_data(priv->message);
  63         }
  64
  65         png_read_info(priv->png, priv->info);
  66         png_uint_32 width;
  67         png_uint_32 height;
  68         int depth;
  69         int color;
  70         png_get_IHDR(priv->png, priv->info, &width, &height, &depth, &color, &priv->interlace, 0, 0);
  71         unsigned nchans = png_get_channels(priv->png, priv->info);
  72
  73         if(depth!=8)
  74                 throw unsupported_image_format("depth!=8");
  75
  76         data.width = width;
  77         data.height = height;
  78         data.stride = data.width*nchans;
  79
  80         switch(color)
  81         {
  82         case PNG_COLOR_TYPE_PALETTE:    data.fmt = COLOR_INDEX; break;
  83         case PNG_COLOR_TYPE_GRAY:       data.fmt = LUMINANCE; break;
  84         case PNG_COLOR_TYPE_GRAY_ALPHA: data.fmt = LUMINANCE_ALPHA; break;
  85         case PNG_COLOR_TYPE_RGB:        data.fmt = (nchans==4 ? RGBX : RGB); break;
  86         case PNG_COLOR_TYPE_RGB_ALPHA:  data.fmt = RGBA; break;
  87         default: throw unsupported_image_format("unknown color type");
  88         }
  89 }
  90
  91 void PngLoader::load_pixels_(Image::Data &data)
  92 {
  93         png_byte **rows = 0;
  94
  95         if(setjmp(png_jmpbuf(priv->png)))
  96         {
  97                 delete[] rows;
  98                 throw bad_image_data(priv->message);
  99         }
 100
 101         if(priv->interlace==PNG_INTERLACE_ADAM7)
 102         {
 103                 // ADAM7 requires all rows to be loaded at once
 104                 unsigned n_passes = png_set_interlace_handling(priv->png);
 105                 rows = new png_byte *[data.height];
 106                 for(unsigned y=0; y<data.height; ++y)
 107                         rows[y] = reinterpret_cast<png_byte *>(data.pixels+data.stride*(data.height-1-y));
 108
 109                 for(unsigned i=0; i<n_passes; ++i)
 110                         png_read_rows(priv->png, rows, 0, data.height);
 111
 112                 delete[] rows;
 113                 rows = 0;
 114         }
 115         else
 116         {
 117                 for(unsigned y=0; y<data.height; ++y)
 118                         png_read_row(priv->png, reinterpret_cast<png_byte *>(data.pixels+data.stride*(data.height-1-y)), 0);
 119         }
 120
 121         png_read_end(priv->png, 0);
 122 }
 123
 124 } // namespace Graphics
 125 } // namespace Msp