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/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package com.github.ojil.algorithm;

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;

/**
 * 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).
 The output image
 * replaces the input.
 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.
 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.
     * 
     * The output is an RgbImage with the HSV values stored in the corresponding
     * RGB bytes.
     * 
     * @param imageInput
     *            input RgbImage
     * @throws ImageError
     *             if input is not an RgbImage.
     */
    @Override
    public void push(final Image imageInput) throws ImageError {
        if (!(imageInput instanceof RgbImage)) {
            throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.IMAGE_NOT_RGBIMAGE, imageInput.toString(), null, null);
        }
        final RgbImage rgbInput = (RgbImage) imageInput;
        final Integer[] rgbData = rgbInput.getData();
        for (int i = 0; i < (rgbInput.getWidth() * rgbInput.getHeight()); i++) {
            final int nR = RgbVal.getR(rgbData[i]);
            final int nG = RgbVal.getG(rgbData[i]);
            final 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.
                    final int nHue = Math.min(239, nHueOffset + ((40 * (nMid - nMin)) / (nMax - nMin)));
                    // compute saturation scaled from 0-255.
                    final 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);
    }
    
}