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// Copyright (C) 2010 Davis E. King (davis@dlib.net), Nils Labugt
// License: Boost Software License See LICENSE.txt for the full license.
#ifndef DLIB_JPEG_LOADER_CPp_
#define DLIB_JPEG_LOADER_CPp_
// only do anything with this file if DLIB_JPEG_SUPPORT is defined
#ifdef DLIB_JPEG_SUPPORT
#include "../array2d.h"
#include "../pixel.h"
#include "../dir_nav.h"
#include "jpeg_loader.h"
#include <stdio.h>
#include <jpeglib.h>
#include <sstream>
#include <setjmp.h>
namespace dlib
{
// ----------------------------------------------------------------------------------------
jpeg_loader::
jpeg_loader( const char* filename ) : height_( 0 ), width_( 0 ), output_components_(0)
{
read_image( filename );
}
// ----------------------------------------------------------------------------------------
jpeg_loader::
jpeg_loader( const std::string& filename ) : height_( 0 ), width_( 0 ), output_components_(0)
{
read_image( filename.c_str() );
}
// ----------------------------------------------------------------------------------------
jpeg_loader::
jpeg_loader( const dlib::file& f ) : height_( 0 ), width_( 0 ), output_components_(0)
{
read_image( f.full_name().c_str() );
}
// ----------------------------------------------------------------------------------------
bool jpeg_loader::is_gray() const
{
return (output_components_ == 1);
}
// ----------------------------------------------------------------------------------------
bool jpeg_loader::is_rgb() const
{
return (output_components_ == 3);
}
// ----------------------------------------------------------------------------------------
struct jpeg_loader_error_mgr
{
jpeg_error_mgr pub; /* "public" fields */
jmp_buf setjmp_buffer; /* for return to caller */
};
void jpeg_loader_error_exit (j_common_ptr cinfo)
{
/* cinfo->err really points to a jpeg_loader_error_mgr struct, so coerce pointer */
jpeg_loader_error_mgr* myerr = (jpeg_loader_error_mgr*) cinfo->err;
/* Return control to the setjmp point */
longjmp(myerr->setjmp_buffer, 1);
}
// ----------------------------------------------------------------------------------------
void jpeg_loader::read_image( const char* filename )
{
if ( filename == NULL )
{
throw image_load_error("jpeg_loader: invalid filename, it is NULL");
}
FILE *fp = fopen( filename, "rb" );
if ( !fp )
{
throw image_load_error(std::string("jpeg_loader: unable to open file ") + filename);
}
jpeg_decompress_struct cinfo;
jpeg_loader_error_mgr jerr;
cinfo.err = jpeg_std_error(&jerr.pub);
jerr.pub.error_exit = jpeg_loader_error_exit;
/* Establish the setjmp return context for my_error_exit to use. */
if (setjmp(jerr.setjmp_buffer))
{
/* If we get here, the JPEG code has signaled an error.
* We need to clean up the JPEG object, close the input file, and return.
*/
jpeg_destroy_decompress(&cinfo);
fclose(fp);
throw image_load_error(std::string("jpeg_loader: error while reading ") + filename);
}
jpeg_create_decompress(&cinfo);
jpeg_stdio_src(&cinfo, fp);
jpeg_read_header(&cinfo, TRUE);
jpeg_start_decompress(&cinfo);
height_ = cinfo.output_height;
width_ = cinfo.output_width;
output_components_ = cinfo.output_components;
if (output_components_ != 1 &&
output_components_ != 3)
{
fclose( fp );
jpeg_destroy_decompress(&cinfo);
std::ostringstream sout;
sout << "jpeg_loader: Unsupported number of colors (" << output_components_ << ") in file " << filename;
throw image_load_error(sout.str());
}
std::vector<unsigned char*> rows;
rows.resize(height_);
// size the image buffer
data.resize(height_*width_*output_components_);
// setup pointers to each row
for (unsigned long i = 0; i < rows.size(); ++i)
rows[i] = &data[i*width_*output_components_];
// read the data into the buffer
while (cinfo.output_scanline < cinfo.output_height)
{
jpeg_read_scanlines(&cinfo, &rows[cinfo.output_scanline], 100);
}
jpeg_finish_decompress(&cinfo);
jpeg_destroy_decompress(&cinfo);
fclose( fp );
}
// ----------------------------------------------------------------------------------------
}
#endif // DLIB_JPEG_SUPPORT
#endif // DLIB_JPEG_LOADER_CPp_
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