/* Turn scRGB into greyscale.
 *
 * 17/4/15
 * 	- from scRGB2BW.c
 */

/*

	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 <math.h>

#include <vips/vips.h>

#include "pcolour.h"

/* We can't use VipsColourCode as our parent class. We want to handle
 * alpha ourselves so we can get 16 -> 8 bit conversion right.
 */

typedef struct _VipsscRGB2BW {
	VipsOperation parent_instance;

	VipsImage *in;
	VipsImage *out;
	int depth;
} VipsscRGB2BW;

typedef VipsOperationClass VipsscRGB2BWClass;

G_DEFINE_TYPE(VipsscRGB2BW, vips_scRGB2BW, VIPS_TYPE_OPERATION);

/* Process a buffer of data.
 */
static void
vips_scRGB2BW_line_8(VipsPel *restrict q, float *restrict p,
	int extra_bands, int width)
{
	int i, j;

	for (i = 0; i < width; i++) {
		float R = p[0];
		float G = p[1];
		float B = p[2];

		int g;
		int og;

		vips_col_scRGB2BW_8(R, G, B, &g, &og);

		p += 3;

		q[0] = g;

		q += 1;

		for (j = 0; j < extra_bands; j++)
			q[j] = VIPS_CLIP(0, (int) (p[j] * 255.0), UCHAR_MAX);
		p += extra_bands;
		q += extra_bands;
	}
}

static void
vips_scRGB2BW_line_16(unsigned short *restrict q, float *restrict p,
	int extra_bands, int width)
{
	int i, j;

	for (i = 0; i < width; i++) {
		float R = p[0];
		float G = p[1];
		float B = p[2];

		int g;
		int og;

		vips_col_scRGB2BW_16(R, G, B, &g, &og);

		p += 3;

		q[0] = g;

		q += 1;

		for (j = 0; j < extra_bands; j++)
			q[j] = VIPS_CLIP(0, (int) (p[j] * 65535.0), USHRT_MAX);
		p += extra_bands;
		q += extra_bands;
	}
}

static int
vips_scRGB2BW_gen(VipsRegion *out_region,
	void *seq, void *a, void *b, gboolean *stop)
{
	VipsRegion *ir = (VipsRegion *) seq;
	VipsscRGB2BW *scRGB2BW = (VipsscRGB2BW *) b;
	VipsRect *r = &out_region->valid;
	VipsImage *in = ir->im;

	int y;

	if (vips_region_prepare(ir, r))
		return -1;

	VIPS_GATE_START("vips_scRGB2BW_gen: work");

	for (y = 0; y < r->height; y++) {
		float *p = (float *)
			VIPS_REGION_ADDR(ir, r->left, r->top + y);
		VipsPel *q = (VipsPel *)
			VIPS_REGION_ADDR(out_region, r->left, r->top + y);

		if (scRGB2BW->depth == 16)
			vips_scRGB2BW_line_16((unsigned short *) q, p,
				in->Bands - 3, r->width);
		else
			vips_scRGB2BW_line_8(q, p,
				in->Bands - 3, r->width);
	}

	VIPS_GATE_STOP("vips_scRGB2BW_gen: work");

	return 0;
}

static int
vips_scRGB2BW_build(VipsObject *object)
{
	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS(object);
	VipsscRGB2BW *scRGB2BW = (VipsscRGB2BW *) object;

	VipsImage **t = (VipsImage **) vips_object_local_array(object, 2);

	VipsImage *in;
	VipsBandFormat format;
	VipsInterpretation interpretation;
	VipsImage *out;

	if (VIPS_OBJECT_CLASS(vips_scRGB2BW_parent_class)->build(object))
		return -1;

	in = scRGB2BW->in;
	if (vips_check_bands_atleast(class->nickname, in, 3))
		return -1;

	switch (scRGB2BW->depth) {
	case 16:
		interpretation = VIPS_INTERPRETATION_GREY16;
		format = VIPS_FORMAT_USHORT;
		break;

	case 8:
		interpretation = VIPS_INTERPRETATION_B_W;
		format = VIPS_FORMAT_UCHAR;
		break;

	default:
		vips_error(class->nickname,
			"%s", _("depth must be 8 or 16"));
		return -1;
	}

	if (vips_cast_float(in, &t[0], NULL))
		return -1;
	in = t[0];

	out = vips_image_new();
	if (vips_image_pipelinev(out,
			VIPS_DEMAND_STYLE_THINSTRIP, in, NULL)) {
		g_object_unref(out);
		return -1;
	}
	out->Type = interpretation;
	out->BandFmt = format;
	out->Bands = in->Bands - 2;

	if (vips_image_generate(out,
			vips_start_one, vips_scRGB2BW_gen, vips_stop_one,
			in, scRGB2BW)) {
		g_object_unref(out);
		return -1;
	}

	g_object_set(object, "out", out, NULL);

	return 0;
}

static void
vips_scRGB2BW_class_init(VipsscRGB2BWClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *object_class = (VipsObjectClass *) class;
	VipsOperationClass *operation_class = VIPS_OPERATION_CLASS(class);

	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	object_class->nickname = "scRGB2BW";
	object_class->description = _("convert scRGB to BW");
	object_class->build = vips_scRGB2BW_build;

	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;

	VIPS_ARG_IMAGE(class, "in", 1,
		_("Input"),
		_("Input image"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsscRGB2BW, in));

	VIPS_ARG_IMAGE(class, "out", 100,
		_("Output"),
		_("Output image"),
		VIPS_ARGUMENT_REQUIRED_OUTPUT,
		G_STRUCT_OFFSET(VipsscRGB2BW, out));

	VIPS_ARG_INT(class, "depth", 130,
		_("Depth"),
		_("Output device space depth in bits"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsscRGB2BW, depth),
		8, 16, 8);
}

static void
vips_scRGB2BW_init(VipsscRGB2BW *scRGB2BW)
{
	scRGB2BW->depth = 8;
}

/**
 * vips_scRGB2BW: (method)
 * @in: input image
 * @out: (out): output image
 * @...: %NULL-terminated list of optional named arguments
 *
 * Optional arguments:
 *
 * * @depth: depth of output image in bits
 *
 * Convert an scRGB image to greyscale. Set @depth to 16 to get 16-bit output.
 *
 * If @depth is 16, any extra channels after RGB are
 * multiplied by 256.
 *
 * See also: vips_LabS2LabQ(), vips_sRGB2scRGB(), vips_rad2float().
 *
 * Returns: 0 on success, -1 on error.
 */
int
vips_scRGB2BW(VipsImage *in, VipsImage **out, ...)
{
	va_list ap;
	int result;

	va_start(ap, out);
	result = vips_call_split("scRGB2BW", ap, in, out);
	va_end(ap);

	return result;
}
