Pillow/src/libImaging/PcdDecode.c

/*
 * The Python Imaging Library.
 * $Id$
 *
 * decoder for uncompressed PCD image data.
 *
 * history:
 *	96-05-10 fl	Created
 *	96-05-18 fl	New tables
 *	97-01-25 fl	Use PhotoYCC unpacker
 *
 * notes:
 *	This driver supports uncompressed PCD modes only
 *	(resolutions up to 768x512).
 *
 * Copyright (c) Fredrik Lundh 1996-97.
 * Copyright (c) Secret Labs AB 1997.
 *
 * See the README file for information on usage and redistribution.
 */


#include "Imaging.h"


int
ImagingPcdDecode(Imaging im, ImagingCodecState state, UINT8* buf, Py_ssize_t bytes)
{
    int x;
    int chunk;
    UINT8* out;
    UINT8* ptr;

    ptr = buf;

    chunk = 3 * state->xsize;

    for (;;) {

	/* We need data for two full lines before we can do anything */
	if (bytes < chunk)
	    return ptr - buf;

	/* Unpack first line */
	out = state->buffer;
	for (x = 0; x < state->xsize; x++) {
	    out[0] = ptr[x];
	    out[1] = ptr[(x+4*state->xsize)/2];
	    out[2] = ptr[(x+5*state->xsize)/2];
	    out += 3;
	}

	state->shuffle((UINT8*) im->image[state->y],
		       state->buffer, state->xsize);

	if (++state->y >= state->ysize)
	    return -1; /* This can hardly happen */

	/* Unpack second line */
	out = state->buffer;
	for (x = 0; x < state->xsize; x++) {
	    out[0] = ptr[x+state->xsize];
	    out[1] = ptr[(x+4*state->xsize)/2];
	    out[2] = ptr[(x+5*state->xsize)/2];
	    out += 3;
	}

	state->shuffle((UINT8*) im->image[state->y],
		       state->buffer, state->xsize);

	if (++state->y >= state->ysize)
	    return -1;

	ptr += chunk;
	bytes -= chunk;

    }
}