gtkradiant/libs/jpeg6/jpgload.cpp

    
#include "radiant_jpeglib.h"
#include "jerror.h"
#include <memory.h>

GLOBAL int LoadJPGBuff(unsigned char *fbuffer, int bufsize, unsigned char **pic, int *width, int *height ) 
{

  /* This struct contains the JPEG decompression parameters and pointers to
   * working space (which is allocated as needed by the JPEG library).
   */
  struct jpeg_decompress_struct cinfo;
  /* We use our private extension JPEG error handler.
   * Note that this struct must live as long as the main JPEG parameter
   * struct, to avoid dangling-pointer problems.
   */
  /* This struct represents a JPEG error handler.  It is declared separately
   * because applications often want to supply a specialized error handler
   * (see the second half of this file for an example).  But here we just
   * take the easy way out and use the standard error handler, which will
   * print a message on stderr and call exit() if compression fails.
   * Note that this struct must live as long as the main JPEG parameter
   * struct, to avoid dangling-pointer problems.
   */

  struct jpeg_error_mgr jerr;
  /* More stuff */
  JSAMPARRAY buffer;		/* Output row buffer */
  int row_stride;		/* physical row width in output buffer */
  unsigned char *out, *bbuf;
  int nSize;
  int jmpret;

  // Rad additions: initialize the longjmp buffer
  jmpret = setjmp( rad_loadfailed );
  if (jmpret != 0)
  {
    *pic = (unsigned char *)rad_errormsg;
    return -1;
  }

  /* Step 1: allocate and initialize JPEG decompression object */

  /* We have to set up the error handler first, in case the initialization
   * step fails.  (Unlikely, but it could happen if you are out of memory.)
   * This routine fills in the contents of struct jerr, and returns jerr's
   * address which we place into the link field in cinfo.
   */
  cinfo.err = jpeg_std_error(&jerr);

  /* Now we can initialize the JPEG decompression object. */
  jpeg_create_decompress(&cinfo);

  /* Step 2: specify data source (eg, a file) */

  jpeg_stdio_src(&cinfo, fbuffer, bufsize);

  /* Step 3: read file parameters with jpeg_read_header() */

  (void) jpeg_read_header(&cinfo, TRUE);
  /* We can ignore the return value from jpeg_read_header since
   *   (a) suspension is not possible with the stdio data source, and
   *   (b) we passed TRUE to reject a tables-only JPEG file as an error.
   * See libjpeg.doc for more info.
   */

  /* Step 4: set parameters for decompression */

  /* In this example, we don't need to change any of the defaults set by
   * jpeg_read_header(), so we do nothing here.
   */

  /* Step 5: Start decompressor */

  (void) jpeg_start_decompress(&cinfo);
  /* We can ignore the return value since suspension is not possible
   * with the stdio data source.
   */
  
  /* ydnar: radiant only handles RGB, non-progressive format jpegs */
  if( cinfo.output_components != 4 )
  {
	*pic = (unsigned char*) "Non-RGB JPEG encountered (unsupported)";
    return -1;
  }
  if( cinfo.progressive_mode )
  {
	*pic = (unsigned char*) "Progressive JPEG encountered (unsupported)";
    return -1;
  }
  
  /* We may need to do some setup of our own at this point before reading
   * the data.  After jpeg_start_decompress() we have the correct scaled
   * output image dimensions available, as well as the output colormap
   * if we asked for color quantization.
   * In this example, we need to make an output work buffer of the right size.
   */ 
  
  /* JSAMPLEs per row in output buffer */
  row_stride = cinfo.output_width * cinfo.output_components;
  nSize = cinfo.output_width*cinfo.output_height*cinfo.output_components;
  
  out = reinterpret_cast<unsigned char*>( malloc( nSize+ 1 ) );
  memset( out, 255, nSize + 1 );
  
  *pic = out;
  *width = cinfo.output_width;
  *height = cinfo.output_height;

  /* Step 6: while (scan lines remain to be read) */
  /*           jpeg_read_scanlines(...); */

  /* Here we use the library's state variable cinfo.output_scanline as the
   * loop counter, so that we don't have to keep track ourselves.
   */
  while (cinfo.output_scanline < cinfo.output_height)
  {
    /* jpeg_read_scanlines expects an array of pointers to scanlines.
     * Here the array is only one element long, but you could ask for
     * more than one scanline at a time if that's more convenient.
     */
	bbuf = out + row_stride * cinfo.output_scanline;
  	buffer = &bbuf;
    (void) jpeg_read_scanlines( &cinfo, buffer, 1 );
  }

  // clear all the alphas to 255
  {
    int i, j;
    unsigned char *buf;

    buf = *pic;

    j = cinfo.output_width * cinfo.output_height * 4;
    for ( i = 3 ; i < j ; i+=4 ) {
      buf[i] = 255;
    }
  }

  /* Step 7: Finish decompression */

  (void) jpeg_finish_decompress(&cinfo);
  /* We can ignore the return value since suspension is not possible
   * with the stdio data source.
   */

  /* Step 8: Release JPEG decompression object */

  /* This is an important step since it will release a good deal of memory. */
  jpeg_destroy_decompress(&cinfo);

  /* After finish_decompress, we can close the input file.
   * Here we postpone it until after no more JPEG errors are possible,
   * so as to simplify the setjmp error logic above.  (Actually, I don't
   * think that jpeg_destroy can do an error exit, but why assume anything...)
   */
  //free (fbuffer);

  /* At this point you may want to check to see whether any corrupt-data
   * warnings occurred (test whether jerr.pub.num_warnings is nonzero).
   */

  /* And we're done! */
  return 0;
}