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/*
 * RgbAvgGray.java
 *
 * Created on August 27, 2006, 8:28 AM
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 *
 * 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.Gray8Image;
import com.github.ojil.core.Image;
import com.github.ojil.core.ImageError;
import com.github.ojil.core.PipelineStage;
import com.github.ojil.core.RgbImage;
import com.github.ojil.core.RgbVal;

/**
 * Pipeline stage converts an ARGB color image into a Gray8Image by measuring
 * difference from a defined color. Pixels equal to the defined color get value
 * Byte.MIN_VALUE. Other pixels get sum of absolute difference between their
 * color and the defined color.
 * 

* For use when looking for objects of a given color. Thresholding or edge * detection should isolate the object. * * @author webb */ public class RgbAbsDiffGray extends PipelineStage { int nR, nG, nB; /** Creates a new instance of RgbAvgGray */ public RgbAbsDiffGray(final int nRGB) { nR = RgbVal.getR(nRGB); nG = RgbVal.getG(nRGB); nB = RgbVal.getB(nRGB); } /** * Implementation of push operation from PipelineStage. Averages the R, G, * and B values to create a gray image of the same size. Note that the * RGB->Gray conversion involves changing the data range of each pixel from * 0->255 to -128->127 because byte is a signed type. * * @param image * the input image * @throws ImageError * if image is not an RgbImage */ @Override public void push(final Image image) throws ImageError { if (!(image instanceof RgbImage)) { throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.IMAGE_NOT_RGBIMAGE, image.toString(), null, null); } final RgbImage rgb = (RgbImage) image; final Integer[] rgbData = rgb.getData(); final Gray8Image gray = new Gray8Image<>(image.getWidth(), image.getHeight()); final Byte[] grayData = gray.getData(); for (int i = 0; i < (image.getWidth() * image.getHeight()); i++) { /* * get individual r, g, and b values, unmasking them from the ARGB * word. */ final byte r = RgbVal.getR(rgbData[i]); final byte g = RgbVal.getG(rgbData[i]); final byte b = RgbVal.getB(rgbData[i]); /* * average the values to get the grayvalue */ grayData[i] = (byte) (Math.min(Byte.MAX_VALUE, ((Math.abs(r - nR) + Math.abs(g - nG) + Math.abs(b - nB)) / 3) + Byte.MIN_VALUE)); } super.setOutput(gray); } }





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