gl2png.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 "gl2png.h"
 
#if !defined(HAVE_LIBPNG)
 
void create_png(FILE *file, PixelBuffer *buffer, int quality)
{
  Msg::Error("This version of Gmsh was compiled without PNG support");
}
 
#else
 
#include <png.h>
 
#ifndef png_jmpbuf
#define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf)
#endif
 
void create_png(FILE *file, PixelBuffer *buffer, int quality)
{
  if((buffer->getFormat() != GL_RGB && buffer->getFormat() != GL_RGBA) ||
     buffer->getType() != GL_UNSIGNED_BYTE) {
    Msg::Error("PNG only implemented for GL_RGB/GL_RGBA and GL_UNSIGNED_BYTE");
    return;
  }
 
  png_structp png_ptr =
    png_create_write_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
 
  if(png_ptr == nullptr) {
    Msg::Error("Could not create PNG write struct");
    return;
  }
 
  png_infop info_ptr = png_create_info_struct(png_ptr);
 
  if(info_ptr == nullptr) {
    png_destroy_write_struct(&png_ptr, nullptr);
    Msg::Error("Could not create PNG info struct");
    return;
  }
 
  if(setjmp(png_jmpbuf(png_ptr))) {
    png_destroy_write_struct(&png_ptr, &info_ptr);
    Msg::Error("Could not setjmp in PNG");
    return;
  }
 
  png_init_io(png_ptr, file);
 
  int height = buffer->getHeight();
  int width = buffer->getWidth();
  int numcomp = buffer->getNumComp();
 
  // png_set_compression_level(png_ptr, 5);
  png_set_IHDR(png_ptr, info_ptr, width, height, 8,
               (numcomp == 3) ? PNG_COLOR_TYPE_RGB : PNG_COLOR_TYPE_RGBA,
               PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE,
               PNG_FILTER_TYPE_BASE);
  time_t now;
  time(&now);
  png_text text_ptr[10];
  text_ptr[0].key = (char *)"Creator";
  text_ptr[0].text = (char *)"Gmsh";
  text_ptr[0].compression = PNG_TEXT_COMPRESSION_NONE;
  text_ptr[1].key = (char *)"Date";
  text_ptr[1].text = ctime(&now);
  text_ptr[1].compression = PNG_TEXT_COMPRESSION_NONE;
  png_set_text(png_ptr, info_ptr, text_ptr, 2);
  png_write_info(png_ptr, info_ptr);
 
  unsigned char *pixels = (unsigned char *)buffer->getPixels();
  for(int row = height - 1; row >= 0; row--) {
    unsigned char *row_pointer = &pixels[row * width * numcomp];
    png_write_row(png_ptr, (png_bytep)row_pointer);
  }
  png_write_end(png_ptr, info_ptr);
  png_destroy_write_struct(&png_ptr, &info_ptr);
}
 
#endif