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package jjil.algorithm;
import jjil.core.Error;
import jjil.core.Image;
import jjil.core.PipelineStage;
import jjil.core.RgbImage;
import jjil.core.RgbVal;
/**
* Converts an RGB image to an HSV image. The HSV values are
* scaled to fit in a byte and are stored in a packed word
* like RGB with the bytes in the same order and position.
* (H→R, S→G, V→B).</br>
* The output image replaces the input.</br>
* Hue runs from Byte.MIN_VALUE to Byte.MIN_VALUE + 239. Hue
* is divided into 3 80-value ranges in the order red, green, blue.
* Saturation and value run from Byte.MIN_VALUE to Byte.MAX_VALUE.</br>
* The code here was adapted from
* http://ilab.usc.edu/wiki/index.php/HSV_And_H2SV_Color_Space
* with changes to scale everything so it fit in byte values.
* @author webb
*/
public class RgbHsv extends PipelineStage {
/**
* Converts an input RGB image into an HSV image. The input is replaced
* by the output.<p>
* The output is an RgbImage with the HSV values stored in the corresponding
* RGB bytes.
* @param imageInput input RgbImage
* @throws jjil.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 rgbInput = (RgbImage) imageInput;
int[] rgbData = rgbInput.getData();
for (int i=0; i<rgbInput.getWidth()*rgbInput.getHeight(); i++) {
int nR = RgbVal.getR(rgbData[i]);
int nG = RgbVal.getG(rgbData[i]);
int nB = RgbVal.getB(rgbData[i]);
int nMax, nMid, nMin;
int nHueOffset;
// determine color order
if (nR > nG && nR > nB) {
// red is max
nMax = nR;
nHueOffset = 0;
if (nG > nB) {
nMid = nG;
nMin = nB;
} else {
nMid = nB;
nMin = nG;
}
} else if (nG > nR && nG > nB) {
// green is max
nMax = nG;
nHueOffset = 80;
if (nR > nB) {
nMid = nR;
nMin = nB;
} else {
nMid = nB;
nMin = nR;
}
} else {
// blue is max
nMax = nB;
nHueOffset = 160;
if (nR > nG) {
nMid = nR;
nMin = nG;
} else {
nMid = nG;
nMin = nR;
}
}
// if the max value is Byte.MIN_VALUE the RGB value
// = 0 so the HSV value = 0 and needs no change.
if (nMax > Byte.MIN_VALUE) {
if (nMax == nMin) {
// color is gray. Hue, saturation are 0.
rgbData[i] = RgbVal.toRgb(
Byte.MIN_VALUE,
Byte.MIN_VALUE,
(byte) nMax);
} else {
// compute hue scaled from 0-240.
int nHue = Math.min(239, nHueOffset + (40 * (nMid - nMin))
/ (nMax - nMin));
// compute saturation scaled from 0-255.
int nSat = Math.min(255, (256 * (nMax - nMin))
/ (nMax - Byte.MIN_VALUE));
rgbData[i] = RgbVal.toRgb(
(byte) (nHue + Byte.MIN_VALUE),
(byte) (nSat + Byte.MIN_VALUE),
(byte) nMax);
}
}
}
super.setOutput(rgbInput);
}
}