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/************************************************************************
PNG image file format support.
The I/O code in this file was originally based on the example.c
skeleton code distributed with the PNG library.
$Id: raster-png.cxx 427 2004-09-27 04:45:31Z garland $
************************************************************************/
#include <vector>
#include <gfx/gfx.h>
#include <gfx/raster.h>
#ifdef HAVE_LIBPNG
#include <png.h>
namespace gfx
{
ByteRaster *read_png_image(const char *file_name)
{
FILE *fp = fopen(file_name, "rb");
if( !fp ) return NULL;
// The last three arguments can be used to set up error handling callbacks.
png_structp png_ptr =
png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
if( !png_ptr ) { fclose(fp); return NULL; }
// Allocate required structure to hold memory information.
png_infop info_ptr = png_create_info_struct(png_ptr);
if( !info_ptr )
{
fclose(fp);
png_destroy_read_struct(&png_ptr, NULL, NULL);
return NULL;
}
// Because we didn't set up any error handlers, we need to be
// prepared to handle longjmps out of the library on error
// conditions.
if( setjmp(png_ptr->jmpbuf) )
{
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
fclose(fp);
return NULL;
}
png_init_io(png_ptr, fp);
// Read in all the image information
png_read_info(png_ptr, info_ptr);
// Get the header for the first image chunk
png_uint_32 width, height;
int bit_depth, color_type, interlace_type;
png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
&interlace_type, NULL, NULL);
////////////////////////////////////////////////////////////////
// the following tell the PNG library how to transform the image
// during input
if( bit_depth == 16 )
// truncate 16 bits/pixel to 8 bits/pixel
png_set_strip_16(png_ptr);
if( color_type == PNG_COLOR_TYPE_PALETTE )
// expand paletted colors into RGB color values
png_set_expand(png_ptr);
else if( color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8 )
// expand grayscale images to full 8 bits/pixel
png_set_expand(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) )
png_set_expand(png_ptr);
// update the palette and info structure
png_read_update_info(png_ptr, info_ptr);
// read the image data
std::vector<png_bytep> row_pointers(height);
int row;
int nchan = png_get_channels(png_ptr, info_ptr);
int nbytes = png_get_rowbytes(png_ptr, info_ptr);
for (row = 0; row < height; row++)
row_pointers[row] = (png_bytep)malloc(nbytes);
png_read_image(png_ptr, &row_pointers.front());
png_read_end(png_ptr, info_ptr);
// Read it into a ByteRaster structure
ByteRaster *img = new ByteRaster(width, height, nchan);
unsigned char *pixel = img->pixel(0,0);
for(row=0; row<height; row++)
{
memcpy(pixel, row_pointers[row], nbytes);
pixel += nbytes;
}
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
for(row=0; row<height; row++) free(row_pointers[row]);
fclose(fp);
return img;
}
bool write_png_image(const char *file_name, const ByteRaster& img)
{
FILE *fp = fopen(file_name, "wb");
if( !fp ) return false;
png_structp png_ptr =
png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
if( !png_ptr ) { fclose(fp); return false; }
png_infop info_ptr = png_create_info_struct(png_ptr);
if( !info_ptr )
{
fclose(fp);
png_destroy_write_struct(&png_ptr, (png_infopp)NULL);
return false;
}
if( setjmp(png_ptr->jmpbuf) )
{
fclose(fp);
png_destroy_write_struct(&png_ptr, (png_infopp)NULL);
return false;
}
png_init_io(png_ptr, fp);
int img_type = PNG_COLOR_TYPE_RGB;
switch( img.channels() )
{
case 1: img_type=PNG_COLOR_TYPE_GRAY; break;
case 2: img_type=PNG_COLOR_TYPE_GRAY_ALPHA; break;
case 4: img_type=PNG_COLOR_TYPE_RGB_ALPHA; break;
}
png_set_IHDR(png_ptr, info_ptr,
img.width(), img.height(), 8, img_type, PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
png_write_info(png_ptr, info_ptr);
std::vector<png_bytep> row_pointers(img.height());
for(int k=0; k<img.height(); k++)
row_pointers[k] = (png_bytep)img.head() +k*img.width()*img.channels();
png_write_image(png_ptr, &row_pointers.front());
png_write_end(png_ptr, info_ptr);
png_destroy_write_struct(&png_ptr, (png_infopp)NULL);
fclose(fp);
return true;
}
} // namespace gfx
#else
namespace gfx
{
bool write_png_image(const char *, const ByteRaster&) { return false; }
ByteRaster *read_png_image(const char *) { return NULL; }
} // namespace gfx
#endif
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