gd_jpeg.c

Linux/Unix下的绘图函数库（Graphic Drawing Library）

	    {
	      fprintf (stderr, "gd-jpeg: error: jpeg_read_scanlines"
		       " returns %u, expected 1\n", nrows);
	      goto error;
	    }
	  for (j = 0; j < cinfo.output_width; j++, currow += 4, tpix++)
	    {
	      *tpix =
		CMYKToRGB (currow[0], currow[1], currow[2], currow[3],
			   inverted);
	    }
	}
    }
  else
    {
      for (i = 0; i < cinfo.output_height; i++)
	{
	  register JSAMPROW currow = row;
	  register int *tpix = im->tpixels[i];
	  nrows = jpeg_read_scanlines (&cinfo, rowptr, 1);
	  if (nrows != 1)
	    {
	      fprintf (stderr, "gd-jpeg: error: jpeg_read_scanlines"
		       " returns %u, expected 1\n", nrows);
	      goto error;
	    }
	  for (j = 0; j < cinfo.output_width; j++, currow += 3, tpix++)
	    {
	      *tpix = gdTrueColor (currow[0], currow[1], currow[2]);
	    }
	}
    }
  if (jpeg_finish_decompress (&cinfo) != TRUE)
    fprintf (stderr, "gd-jpeg: warning: jpeg_finish_decompress"
	     " reports suspended data source\n");
  /* TBB 2.0.29: we should do our best to read whatever we can read, and a 
    warning is a warning. A fatal error on warnings doesn't make sense. */
#if 0
  /* This was originally added by Truxton Fulton */
  if (cinfo.err->num_warnings > 0)
    goto error;
#endif

  jpeg_destroy_decompress (&cinfo);
  gdFree (row);
  return im;

error:
  jpeg_destroy_decompress (&cinfo);
  if (row)
    gdFree (row);
  if (im)
    gdImageDestroy (im);
  return 0;
}

/* A very basic conversion approach, TBB */

static int
CMYKToRGB (int c, int m, int y, int k, int inverted)
{
  if (inverted)
    {
      c = 255 - c;
      m = 255 - m;
      y = 255 - y;
      k = 255 - k;
    }
  return gdTrueColor ((255 - c) * (255 - k) / 255,
		      (255 - m) * (255 - k) / 255,
		      (255 - y) * (255 - k) / 255);
#if 0
  if (inverted)
    {
      c = 255 - c;
      m = 255 - m;
      y = 255 - y;
      k = 255 - k;
    }
  c = c * (255 - k) / 255 + k;
  if (c > 255)
    {
      c = 255;
    }
  if (c < 0)
    {
      c = 0;
    }
  m = m * (255 - k) / 255 + k;
  if (m > 255)
    {
      m = 255;
    }
  if (m < 0)
    {
      m = 0;
    }
  y = y * (255 - k) / 255 + k;
  if (y > 255)
    {
      y = 255;
    }
  if (y < 0)
    {
      y = 0;
    }
  c = 255 - c;
  m = 255 - m;
  y = 255 - y;
  return gdTrueColor (c, m, y);
#endif
}

/*

 * gdIOCtx JPEG data sources and sinks, T. Boutell
 * almost a simple global replace from T. Lane's stdio versions.
 *
 */

/* Different versions of libjpeg use either 'jboolean' or 'boolean', and
   some platforms define 'boolean', and so forth. Deal with this
   madness by typedeffing 'safeboolean' to 'boolean' if HAVE_BOOLEAN
   is already set, because this is the test that libjpeg uses.
   Otherwise, typedef it to int, because that's what libjpeg does
   if HAVE_BOOLEAN is not defined. -TBB */

#ifdef HAVE_BOOLEAN
typedef boolean safeboolean;
#else
typedef int safeboolean;
#endif /* HAVE_BOOLEAN */

/* Expanded data source object for gdIOCtx input */

typedef struct
{
  struct jpeg_source_mgr pub;	/* public fields */

  gdIOCtx *infile;		/* source stream */
  unsigned char *buffer;	/* start of buffer */
  safeboolean start_of_file;	/* have we gotten any data yet? */

}
my_source_mgr;

typedef my_source_mgr *my_src_ptr;

#define INPUT_BUF_SIZE  4096	/* choose an efficiently fread'able size */

/*
 * Initialize source --- called by jpeg_read_header
 * before any data is actually read.
 */

void
init_source (j_decompress_ptr cinfo)
{
  my_src_ptr src = (my_src_ptr) cinfo->src;

  /* We reset the empty-input-file flag for each image,
   * but we don't clear the input buffer.
   * This is correct behavior for reading a series of images from one source.
   */
  src->start_of_file = TRUE;
}


/*
 * Fill the input buffer --- called whenever buffer is emptied.
 *
 * In typical applications, this should read fresh data into the buffer
 * (ignoring the current state of next_input_byte & bytes_in_buffer),
 * reset the pointer & count to the start of the buffer, and return TRUE
 * indicating that the buffer has been reloaded.  It is not necessary to
 * fill the buffer entirely, only to obtain at least one more byte.
 *
 * There is no such thing as an EOF return.  If the end of the file has been
 * reached, the routine has a choice of ERREXIT() or inserting fake data into
 * the buffer.  In most cases, generating a warning message and inserting a
 * fake EOI marker is the best course of action --- this will allow the
 * decompressor to output however much of the image is there.  However,
 * the resulting error message is misleading if the real problem is an empty
 * input file, so we handle that case specially.
 *
 * In applications that need to be able to suspend compression due to input
 * not being available yet, a FALSE return indicates that no more data can be
 * obtained right now, but more may be forthcoming later.  In this situation,
 * the decompressor will return to its caller (with an indication of the
 * number of scanlines it has read, if any).  The application should resume
 * decompression after it has loaded more data into the input buffer.  Note
 * that there are substantial restrictions on the use of suspension --- see
 * the documentation.
 *
 * When suspending, the decompressor will back up to a convenient restart point
 * (typically the start of the current MCU). next_input_byte & bytes_in_buffer
 * indicate where the restart point will be if the current call returns FALSE.
 * Data beyond this point must be rescanned after resumption, so move it to
 * the front of the buffer rather than discarding it.
 */

#define END_JPEG_SEQUENCE "\r\n[*]--:END JPEG:--[*]\r\n"
safeboolean
fill_input_buffer (j_decompress_ptr cinfo)
{
  my_src_ptr src = (my_src_ptr) cinfo->src;
  /* 2.0.12: signed size. Thanks to Geert Jansen */
  /* 2.0.14: some platforms (mingw-msys) don't have ssize_t. Call 
     an int an int. */
  int nbytes = 0;
  memset (src->buffer, 0, INPUT_BUF_SIZE);

  while (nbytes < INPUT_BUF_SIZE)
    {

      int got = gdGetBuf (src->buffer + nbytes,
			  INPUT_BUF_SIZE - nbytes,
			  src->infile);

      if ((got == EOF) || (got == 0))
	{

	  /* EOF or error. If we got any data, don't worry about it.
	     If we didn't, then this is unexpected. */
	  if (!nbytes)
	    {

	      nbytes = -1;

	    }

	  break;

	}

      nbytes += got;

    }

  if (nbytes <= 0)
    {
      if (src->start_of_file)	/* Treat empty input file as fatal error */
	ERREXIT (cinfo, JERR_INPUT_EMPTY);
      WARNMS (cinfo, JWRN_JPEG_EOF);
      /* Insert a fake EOI marker */
      src->buffer[0] = (unsigned char) 0xFF;
      src->buffer[1] = (unsigned char) JPEG_EOI;
      nbytes = 2;
    }

  src->pub.next_input_byte = src->buffer;
  src->pub.bytes_in_buffer = nbytes;
  src->start_of_file = FALSE;

  return TRUE;
}


/*
 * Skip data --- used to skip over a potentially large amount of
 * uninteresting data (such as an APPn marker).
 *
 * Writers of suspendable-input applications must note that skip_input_data
 * is not granted the right to give a suspension return.  If the skip extends
 * beyond the data currently in the buffer, the buffer can be marked empty so
 * that the next read will cause a fill_input_buffer call that can suspend.
 * Arranging for additional bytes to be discarded before reloading the input
 * buffer is the application writer's problem.
 */

void
skip_input_data (j_decompress_ptr cinfo, long num_bytes)
{
  my_src_ptr src = (my_src_ptr) cinfo->src;

  /* Just a dumb implementation for now. Not clear that being smart is worth
   * any trouble anyway --- large skips are infrequent.
   */
  if (num_bytes > 0)
    {
      while (num_bytes > (long) src->pub.bytes_in_buffer)
	{
	  num_bytes -= (long) src->pub.bytes_in_buffer;
	  (void) fill_input_buffer (cinfo);
	  /* note we assume that fill_input_buffer will never return FALSE,
	   * so suspension need not be handled.
	   */
	}
      src->pub.next_input_byte += (size_t) num_bytes;
      src->pub.bytes_in_buffer -= (size_t) num_bytes;
    }
}


/*
 * An additional method that can be provided by data source modules is the
 * resync_to_restart method for error recovery in the presence of RST markers.
 * For the moment, this source module just uses the default resync method
 * provided by the JPEG library.  That method assumes that no backtracking
 * is possible.
 */


/*
 * Terminate source --- called by jpeg_finish_decompress
 * after all data has been read.  Often a no-op.
 *
 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
 * application must deal with any cleanup that should happen even
 * for error exit.
 */

void
term_source (j_decompress_ptr cinfo)
{

#if 0
/* never used */
  my_src_ptr src = (my_src_ptr) cinfo->src;

#endif
}


/*
 * Prepare for input from a gdIOCtx stream.
 * The caller must have already opened the stream, and is responsible
 * for closing it after finishing decompression.
 */

void
jpeg_gdIOCtx_src (j_decompress_ptr cinfo, gdIOCtx * infile)
{
  my_src_ptr src;

  /* The source object and input buffer are made permanent so that a series
   * of JPEG images can be read from the same file by calling jpeg_gdIOCtx_src
   * only before the first one.  (If we discarded the buffer at the end of
   * one image, we'd likely lose the start of the next one.)
   * This makes it unsafe to use this manager and a different source
   * manager serially with the same JPEG object.  Caveat programmer.
   */
  if (cinfo->src == NULL)
    {				/* first time for this JPEG object? */
      cinfo->src = (struct jpeg_source_mgr *)
	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
				    sizeof (my_source_mgr));
      src = (my_src_ptr) cinfo->src;
      src->buffer = (unsigned char *)
	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
				    INPUT_BUF_SIZE * sizeof (unsigned char));

    }

  src = (my_src_ptr) cinfo->src;
  src->pub.init_source = init_source;
  src->pub.fill_input_buffer = fill_input_buffer;
  src->pub.skip_input_data = skip_input_data;
  src->pub.resync_to_restart = jpeg_resync_to_restart;	/* use default method */
  src->pub.term_source = term_source;
  src->infile = infile;
  src->pub.bytes_in_buffer = 0;	/* forces fill_input_buffer on first read */
  src->pub.next_input_byte = NULL;	/* until buffer loaded */
}

/* Expanded data destination object for stdio output */

typedef struct
{
  struct jpeg_destination_mgr pub;	/* public fields */
  gdIOCtx *outfile;		/* target stream */
  unsigned char *buffer;	/* start of buffer */
}
my_destination_mgr;

typedef my_destination_mgr *my_dest_ptr;

#define OUTPUT_BUF_SIZE  4096	/* choose an efficiently fwrite'able size */

/*
 * Initialize destination --- called by jpeg_start_compress
 * before any data is actually written.
 */

void
init_destination (j_compress_ptr cinfo)
{
  my_dest_ptr dest = (my_dest_ptr) cinfo->dest;

  /* Allocate the output buffer --- it will be released when done with image */
  dest->buffer = (unsigned char *)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				OUTPUT_BUF_SIZE * sizeof (unsigned char));

  dest->pub.next_output_byte = dest->buffer;
  dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
}


/*
 * Empty the output buffer --- called whenever buffer fills up.
 *
 * In typical applications, this should write the entire output buffer
 * (ignoring the current state of next_output_byte & free_in_buffer),
 * reset the pointer & count to the start of the buffer, and return TRUE
 * indicating that the buffer has been dumped.
 *
 * In applications that need to be able to suspend compression due to output
 * overrun, a FALSE return indicates that the buffer cannot be emptied now.
 * In this situation, the compressor will return to its caller (possibly with
 * an indication that it has not accepted all the supplied scanlines).  The
 * application should resume compression after it has made more room in the
 * output buffer.  Note that there are substantial restrictions on the use of
 * suspension --- see the documentation.
 *
 * When suspending, the compressor will back up to a convenient restart point
 * (typically the start of the current MCU). next_output_byte & free_in_buffer
 * indicate where the restart point will be if the current call returns FALSE.
 * Data beyond this point will be regenerated after resumption, so do not
 * write it out when emptying the buffer externally.
 */

safeboolean
empty_output_buffer (j_compress_ptr cinfo)
{
  my_dest_ptr dest = (my_dest_ptr) cinfo->dest;

  if (gdPutBuf (dest->buffer, OUTPUT_BUF_SIZE, dest->outfile) !=
      (size_t) OUTPUT_BUF_SIZE)
    ERREXIT (cinfo, JERR_FILE_WRITE);

  dest->pub.next_output_byte = dest->buffer;
  dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;

  return TRUE;
}


/*
 * Terminate destination --- called by jpeg_finish_compress
 * after all data has been written.  Usually needs to flush buffer.
 *
 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
 * application must deal with any cleanup that should happen even
 * for error exit.
 */

void
term_destination (j_compress_ptr cinfo)
{
  my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
  size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer;

  /* Write any data remaining in the buffer */
  if (datacount > 0)
    {
      if (gdPutBuf (dest->buffer, datacount, dest->outfile) != datacount)
	ERREXIT (cinfo, JERR_FILE_WRITE);
    }
}


/*
 * Prepare for output to a stdio stream.
 * The caller must have already opened the stream, and is responsible
 * for closing it after finishing compression.
 */

void
jpeg_gdIOCtx_dest (j_compress_ptr cinfo, gdIOCtx * outfile)
{
  my_dest_ptr dest;

  /* The destination object is made permanent so that multiple JPEG images
   * can be written to the same file without re-executing jpeg_stdio_dest.
   * This makes it dangerous to use this manager and a different destination
   * manager serially with the same JPEG object, because their private object
   * sizes may be different.  Caveat programmer.
   */
  if (cinfo->dest == NULL)
    {				/* first time for this JPEG object? */
      cinfo->dest = (struct jpeg_destination_mgr *)
	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
				    sizeof (my_destination_mgr));
    }

  dest = (my_dest_ptr) cinfo->dest;
  dest->pub.init_destination = init_destination;
  dest->pub.empty_output_buffer = empty_output_buffer;
  dest->pub.term_destination = term_destination;
  dest->outfile = outfile;
}

#endif /* HAVE_LIBJPEG */