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/*
 * Copyright 2007 by Jon A. Webb
 *     This program 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 3 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 Lesser GNU General Public License
 *    along with this program.  If not, see .
 *
 */

package com.github.ojil.algorithm;

import com.github.ojil.core.Error;
import com.github.ojil.core.Gray8Image;
import com.github.ojil.core.Image;
import com.github.ojil.core.PipelineStage;
import com.github.ojil.core.RgbImage;
import com.github.ojil.core.RgbVal;

/**
 * Thresholds an RgbImage based on a given RGB value and another
 * RGB value that represents the masimum RGB distance from the
 * first value that a pixel can lie in to be considered within
 * the threshold.
 * The computation is analogous to a vector distance from a given
 * point. It can be described as 

 *  (rgb - rgbTarget) · rgbVec  < threshold
 * @author webb
 */
public class RgbVecThresh extends PipelineStage {
    private int nR, nG, nB;
    private int nRVec, nGVec, nBVec;
    private int nThresh;
    private boolean bWithin;
    
    /**
     * Initialize class to filter based on given target rgb value
     * and vector distance from the target value measured along
     * a particular vector. The bWithin parameter allows the 
     * threshold test to be reversed -- bWithin = false causes
     * true (Byte.MAX_VALUE) to be output for rgb values > than
     * the test.
     * @param rgbTarget target RGB value
     * @param rgbVec direction and distance of test
     * @param nThresh threshold to compare with
     * @param bWithin if true result is true if < test; if false,
     * result is true if > than the test.
     */
    public RgbVecThresh(int rgbTarget, int rgbVec, int nThresh, boolean bWithin) {
        this.nR = RgbVal.getR(rgbTarget) - Byte.MIN_VALUE;
        this.nG = RgbVal.getG(rgbTarget) - Byte.MIN_VALUE;
        this.nB = RgbVal.getB(rgbTarget) - Byte.MIN_VALUE;
        this.nRVec = RgbVal.getR(rgbVec);
        this.nGVec = RgbVal.getG(rgbVec);
        this.nBVec = RgbVal.getB(rgbVec);
        this.nThresh = nThresh;
        this.bWithin = bWithin;
    }

    /**
     * Perform thresholding operation. Output is a gray image.
     * @param imageInput input RgbImage to be thresholded.
     * @throws com.github.ojil.core.Error if input is not an RgbImage.
     */
    public void push(Image imageInput) throws Error {
        if (!(imageInput instanceof RgbImage)) {
            throw new Error(
                            Error.PACKAGE.ALGORITHM,
                            ErrorCodes.IMAGE_NOT_RGBIMAGE,
                            imageInput.toString(),
                            null,
                            null);
        }
        RgbImage rgb = (RgbImage) imageInput;
        Integer[] nData = rgb.getData();
        Gray8Image imageResult = new Gray8Image(rgb.getWidth(), rgb.getHeight());
        Byte[] bData = imageResult.getData();
        for (int i=0; i