gl2jpeg.cpp

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// Gmsh - Copyright (C) 1997-2022 C. Geuzaine, J.-F. Remacle
//
// See the LICENSE.txt file in the Gmsh root directory for license information.
// Please report all issues on https://gitlab.onelab.info/gmsh/gmsh/issues.
 
#include "GmshConfig.h"
#include "gl2jpeg.h"
#undef EXTERN
 
#if !defined(HAVE_LIBJPEG)
 
void create_jpeg(FILE *outfile, PixelBuffer *buffer, int quality, int smoothing)
{
  Msg::Error("This version of Gmsh was compiled without JPEG support");
}
 
#else
 
extern "C" {
#include <jpeglib.h>
#include <jerror.h>
}
 
static void my_output_message(j_common_ptr cinfo)
{
  char buffer[JMSG_LENGTH_MAX];
 
  (*cinfo->err->format_message)(cinfo, buffer);
 
  Msg::Debug("%s", buffer);
}
 
void create_jpeg(FILE *outfile, PixelBuffer *buffer, int quality, int smoothing)
{
  if(buffer->getFormat() != GL_RGB || buffer->getType() != GL_UNSIGNED_BYTE) {
    Msg::Error("JPEG only implemented for GL_RGB and GL_UNSIGNED_BYTE");
    return;
  }
 
  struct jpeg_compress_struct cinfo;
  struct jpeg_error_mgr jerr;
  cinfo.err = jpeg_std_error(&jerr);
  cinfo.err->output_message = my_output_message;
 
  jpeg_create_compress(&cinfo);
  jpeg_stdio_dest(&cinfo, outfile);
  cinfo.image_width = buffer->getWidth();
  cinfo.image_height = buffer->getHeight();
  cinfo.input_components = 3;
  cinfo.in_color_space = JCS_RGB;
  jpeg_set_defaults(&cinfo);
  jpeg_set_quality(&cinfo, quality, TRUE);
  cinfo.optimize_coding = TRUE;
  cinfo.smoothing_factor = smoothing;
  jpeg_start_compress(&cinfo, TRUE);
 
  unsigned char *pixels = (unsigned char *)buffer->getPixels();
  JSAMPROW row_pointer[1];
  int row_stride = cinfo.image_width * cinfo.input_components;
  int i = cinfo.image_height - 1;
  while(i >= 0) {
    row_pointer[0] = &pixels[i * row_stride];
    (void)jpeg_write_scanlines(&cinfo, row_pointer, 1);
    i--;
  }
  jpeg_finish_compress(&cinfo);
  jpeg_destroy_compress(&cinfo);
}
 
#endif