www.pudn.com > ilib > IJPEG.c

/*
 * IJPEGC.c
 *
 * Image library
 *
 * Description:
 *	JPEG reading and writing
 *	Most of this code was created from the example.c file provided
 *	in the JPEG distribution.
 *
 *	Get the JPEG distribution at:
 *		ftp://ftp.uu.net/graphics/jpeg/
 *	
 *
 * History:
 *	22-Jul-99	Craig Knudsen	cknudsen@radix.net
 *			Created
 *
 ****************************************************************************/

#ifdef HAVE_JPEGLIB

#include 
#include 
#include 
#include 

#include 
#include 

#include "Ilib.h"
#include "IlibP.h"

#define DEFAULT_JPEG_QUALITY	75


IError _IWriteJPEG ( fp, image, options )
FILE *fp;
IImageP *image;
IOptions options;
{
  struct jpeg_compress_struct cinfo;
  struct jpeg_error_mgr jerr;
  JSAMPROW row_pointer[1];
  int loop;

  /* Step 1: allocate and initialize JPEG compression object */
  cinfo.err = jpeg_std_error ( &jerr );
  jpeg_create_compress ( &cinfo );

  /* Step 2: specify data destination (eg, a file) */
  jpeg_stdio_dest ( &cinfo, fp );

  /* Step 3: set parameters for compression */
  cinfo.image_width = image->width;
  cinfo.image_height = image->height;
  if ( image->greyscale ) {
    cinfo.input_components = 1; /* # of color components per pixel */
    cinfo.in_color_space = JCS_GRAYSCALE; /* colorspace of input image */
  } else {
    cinfo.input_components = 3; /* # of color components per pixel */
    cinfo.in_color_space = JCS_RGB; /* colorspace of input image */
  }

  jpeg_set_defaults ( &cinfo );
  jpeg_set_quality ( &cinfo, DEFAULT_JPEG_QUALITY, TRUE );

  /* Step 4: Start compressor */
  jpeg_start_compress ( &cinfo, TRUE );

  /* Step 5: while (scan lines remain to be written) */
  for ( loop = 0; loop < image->height; loop++ ) {
    row_pointer[0] = &image->data[loop * image->width * cinfo.input_components];
    (void) jpeg_write_scanlines ( &cinfo, row_pointer, 1 );
  }

  /* Step 6: Finish compression */
  jpeg_finish_compress ( &cinfo );

  /* Step 7: release JPEG compression object */
  jpeg_destroy_compress ( &cinfo );

  return ( INoError );
}





IError _IReadJPEG ( fp, options, image_return )
FILE *fp;
IOptions options;
IImageP **image_return;
{
  IImageP *image;
  struct jpeg_decompress_struct cinfo;
  struct jpeg_error_mgr jerr;
  JSAMPROW row_pointer[1];
  int loop;
  
  /* We set up the normal JPEG error routines */
  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, fp );

  /* Step 3: read file parameters with jpeg_read_header() */
  (void) jpeg_read_header ( &cinfo, TRUE );

  /* Step 5: Start decompressor */
  (void) jpeg_start_decompress ( &cinfo );

  /* allocate Ilib image as either grayscale or rgb */
  image = (IImageP *) ICreateImage ( cinfo.output_width, cinfo.output_height,
    cinfo.output_components == 1 ? IOPTION_GREYSCALE : IOPTION_NONE );
  image->comments = (char *) malloc ( strlen ( IDEFAULT_COMMENT ) + 1 );
  strcpy ( image->comments, IDEFAULT_COMMENT );

  /* Step 6: while (scan lines remain to be read) */
  for ( loop = 0; loop < cinfo.output_height; loop++ ) {
    row_pointer[0] = &image->data[loop * cinfo.output_width *
      cinfo.output_components];
    (void) jpeg_read_scanlines ( &cinfo, row_pointer, 1 );
  }

  /* Step 7: Finish decompression */
  (void) jpeg_finish_decompress ( &cinfo );

  /* Step 8: Release JPEG decompression object */
  jpeg_destroy_decompress ( &cinfo );

  *image_return = image;

  return ( INoError );
}

#endif