/*
* 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 <http://www.gnu.org/licenses/>.
*
*/
package jjil.algorithm;
import jjil.core.Error;
import jjil.core.Gray8Image;
import jjil.core.Image;
import jjil.core.PipelineStage;
import jjil.core.RgbImage;
import jjil.core.RgbVal;
/**
* Pipeline stage converts an ARGB color image into a Gray8Image. It does
* this by averaging the R, G, and B values. Note that since the byte image
* is signed, each unsigned byte in the ARGB word is converted to a signed
* integer before doing the average. So the word 0x00FF8001 would get
* R, G, and B values 127, 0, and -126 (and the average would be 0).
* @author webb
*/
public class RgbAvgGray extends PipelineStage {
/** Creates a new instance of RgbAvgGray */
public RgbAvgGray() {
}
/** 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 jjil.core.Error if image is not an RgbImage
*/
public void push(Image image) throws jjil.core.Error {
if (!(image instanceof RgbImage)) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.IMAGE_NOT_RGBIMAGE,
image.toString(),
null,
null);
}
RgbImage rgb = (RgbImage) image;
int[] rgbData = rgb.getData();
Gray8Image gray = new Gray8Image(image.getWidth(), image.getHeight());
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.
*/
byte r = RgbVal.getR(rgbData[i]);
byte g = RgbVal.getG(rgbData[i]);
byte b = RgbVal.getB(rgbData[i]);
/* average the values to get the grayvalue
*/
grayData[i] = (byte)((r + g + b) / 3);
}
super.setOutput(gray);
}
}