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src/Source/LibJPEG/rdtarga.c  view on Meta::CPAN

/*
 * rdtarga.c
 *
 * Copyright (C) 1991-1996, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains routines to read input images in Targa format.
 *
 * These routines may need modification for non-Unix environments or
 * specialized applications.  As they stand, they assume input from
 * an ordinary stdio stream.  They further assume that reading begins
 * at the start of the file; start_input may need work if the
 * user interface has already read some data (e.g., to determine that
 * the file is indeed Targa format).
 *
 * Based on code contributed by Lee Daniel Crocker.
 */

#include "cdjpeg.h"		/* Common decls for cjpeg/djpeg applications */

#ifdef TARGA_SUPPORTED


/* Macros to deal with unsigned chars as efficiently as compiler allows */

#ifdef HAVE_UNSIGNED_CHAR
typedef unsigned char U_CHAR;
#define UCH(x)	((int) (x))
#else /* !HAVE_UNSIGNED_CHAR */
#ifdef CHAR_IS_UNSIGNED
typedef char U_CHAR;
#define UCH(x)	((int) (x))
#else
typedef char U_CHAR;
#define UCH(x)	((int) (x) & 0xFF)
#endif
#endif /* HAVE_UNSIGNED_CHAR */


#define	ReadOK(file,buffer,len)	(JFREAD(file,buffer,len) == ((size_t) (len)))


/* Private version of data source object */

typedef struct _tga_source_struct * tga_source_ptr;

typedef struct _tga_source_struct {
  struct cjpeg_source_struct pub; /* public fields */

  j_compress_ptr cinfo;		/* back link saves passing separate parm */

  JSAMPARRAY colormap;		/* Targa colormap (converted to my format) */

  jvirt_sarray_ptr whole_image;	/* Needed if funny input row order */
  JDIMENSION current_row;	/* Current logical row number to read */

  /* Pointer to routine to extract next Targa pixel from input file */
  JMETHOD(void, read_pixel, (tga_source_ptr sinfo));

  /* Result of read_pixel is delivered here: */
  U_CHAR tga_pixel[4];

  int pixel_size;		/* Bytes per Targa pixel (1 to 4) */

  /* State info for reading RLE-coded pixels; both counts must be init to 0 */
  int block_count;		/* # of pixels remaining in RLE block */
  int dup_pixel_count;		/* # of times to duplicate previous pixel */

  /* This saves the correct pixel-row-expansion method for preload_image */
  JMETHOD(JDIMENSION, get_pixel_rows, (j_compress_ptr cinfo,
				       cjpeg_source_ptr sinfo));
} tga_source_struct;


/* For expanding 5-bit pixel values to 8-bit with best rounding */

static const UINT8 c5to8bits[32] = {
    0,   8,  16,  25,  33,  41,  49,  58,
   66,  74,  82,  90,  99, 107, 115, 123,
  132, 140, 148, 156, 165, 173, 181, 189,
  197, 206, 214, 222, 230, 239, 247, 255
};