/* @(#) Function to perform black level correction given black image
 * @(#) designed for PAD camera single field black to apply in blocks
 * @(#) as each is reused for higher resolution pels (eg: 6 8 for Progres)
 * @(#) IM_BANDFMT_UCHAR images only. Always writes UCHAR.
 * @(#) int im_clamp(in, w, out, hstep, vstep)
 * @(#) IMAGE *in, *w, *out;  int hstep, vstep;
 * @(#)	   - Compute clip(image - (black)) ie subtract black no negatives
 * @(#) scales for low res Progres images to replicate black value
 * @(#) Returns 0 on success and -1 on error
 * fiddle at your peril - nasty code
 * Copyright: 1993 KM
 * 20/8/93
 */

/*

	This file is part of VIPS.

	VIPS is free software; you can redistribute it and/or modify
	it under the terms of the GNU Lesser General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	02110-1301  USA

 */

/*

	These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

#include <stdio.h>
#include <stdlib.h>

#include <vips/vips.h>
#include <vips/vips7compat.h>
#include <vips/internal.h>

int
im_clamp(IMAGE *in, IMAGE *out, IMAGE *black, int hstep, int vstep)
{
	PEL *p, *blk, *bline, *bexp;
	PEL *q, *outbuf;
	int rep;
	int x, y, bnd;
	int temp, blacky, newblacky;

	if (im_iocheck(in, out))
		return -1;
	if (in->Bbits != 8 ||
		in->Coding != IM_CODING_NONE || in->BandFmt != IM_BANDFMT_UCHAR) {
		im_error("im_clamp", "%s", _("bad input format"));
		return -1;
	}
	if (black->Bbits != 8 ||
		black->Coding != IM_CODING_NONE || black->BandFmt != IM_BANDFMT_UCHAR) {
		im_error("im_clamp", "%s", _("bad black format"));
		return -1;
	}

	/* Set up the output header.
	 */
	if (im_cp_desc(out, in))
		return -1;
	if (im_setupout(out))
		return -1;

	/* Make buffer for expanded black line
	 */
	if (!(bline = (PEL *) im_malloc(out, black->Bands * hstep * in->Xsize)))
		return -1;
	/* Make buffer we write to.
	 */
	if (!(outbuf = (PEL *) im_malloc(out, out->Bands * out->Xsize)))
		return -1;
	blacky = -1;
	p = (PEL *) in->data;

	for (y = 0; y < in->Ysize; y++) {
		/* calc corresponding black line - get new one if different */
		newblacky = (vstep * black->Ysize - in->Ysize + y) / vstep;
		if (newblacky != blacky) {
			blacky = newblacky;
			/* time to expand a new black line */
			blk = (PEL *) (black->data +
				black->Xsize * black->Bands * blacky);
			for (bexp = bline, x = 0; x < black->Xsize; x++) {
				for (rep = 0; rep < hstep; rep++)
					for (q = blk, bnd = 0; bnd < in->Bands; bnd++)
						*bexp++ = *q++;
				blk += black->Bands;
			}
		}

		/* correct a line of image */
		bexp = bline;
		q = outbuf;
		for (x = 0; x < (out->Bands * out->Xsize); x++) {
			temp = ((int) *p++ - *bexp++);
			if (temp < 0)
				temp = 0;
			*q++ = (PEL) temp;
		}

		if (im_writeline(y, out, outbuf))
			return -1;
	} /* end of a line */

	return 0;
}
