/*
 * Copyright 2011, Blender Foundation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU 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 General Public License for more details.
 *
 * You should have received a copy of the GNU 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.
 *
 * Contributor: 
 *		Jeroen Bakker 
 *		Monique Dewanchand
 */

#include "COM_DifferenceMatteOperation.h"
#include "BLI_math.h"

DifferenceMatteOperation::DifferenceMatteOperation() : NodeOperation()
{
	addInputSocket(COM_DT_COLOR);
	addInputSocket(COM_DT_COLOR);
	addOutputSocket(COM_DT_VALUE);

	this->m_inputImage1Program = NULL;
	this->m_inputImage2Program = NULL;
}

void DifferenceMatteOperation::initExecution()
{
	this->m_inputImage1Program = this->getInputSocketReader(0);
	this->m_inputImage2Program = this->getInputSocketReader(1);
}
void DifferenceMatteOperation::deinitExecution()
{
	this->m_inputImage1Program = NULL;
	this->m_inputImage2Program = NULL;
}

void DifferenceMatteOperation::executePixel(float output[4], float x, float y, PixelSampler sampler)
{
	float inColor1[4];
	float inColor2[4];

	const float tolerance = this->m_settings->t1;
	const float falloff = this->m_settings->t2;
	float difference;
	float alpha;

	this->m_inputImage1Program->read(inColor1, x, y, sampler);
	this->m_inputImage2Program->read(inColor2, x, y, sampler);

	difference = (fabsf(inColor2[0] - inColor1[0]) +
	              fabsf(inColor2[1] - inColor1[1]) +
	              fabsf(inColor2[2] - inColor1[2]));

	/* average together the distances */
	difference = difference / 3.0f;

	/* make 100% transparent */
	if (difference < tolerance) {
		output[0] = 0.0f;
	}
	/*in the falloff region, make partially transparent */
	else if (difference < falloff + tolerance) {
		difference = difference - tolerance;
		alpha = difference / falloff;
		/*only change if more transparent than before */
		if (alpha < inColor1[3]) {
			output[0] = alpha;
		}
		else { /* leave as before */
			output[0] = inColor1[3];
		}
	}
	else {
		/* foreground object */
		output[0] = inColor1[3];
	}
}

