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/*
 * Gray3Bands2Rgb.java
 *   Takes 3 gray images and combines them to make an RGB image.
 *   This is not a pipeline stage.
 *
 * Created on August 27, 2006, 9:02 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.ImageError;
import com.github.ojil.core.RgbImage;

/**
 * Gray3Bands2Rgb converts three 8-bit gray images to RGB by copying the three
 * input gray values into R, G, and B. The signed byte values in the gray image
 * are changed into unsigned byte values in the ARGB word.
 *
 * @author webb
 */
public class Gray3Bands2Rgb {
    
    /**
     * Converts 3 8-bit gray images into an RGB image by combining the R, G, and
     * B values. Also changes the data range of the bytes from -128->127 to
     * 0->255 since the bit shift in Java would treat them as signed values
     * otherwise.
     * 
     * @param imRed
     *            the input red image.
     * @param imGreen
     *            the input green image.
     * @param imBlue
     *            the input blue image.
     * @return the color image
     * @throws ImageError
     *             if the input sizes do not match
     */
    static public RgbImage push(final Gray8Image imRed, final Gray8Image imGreen, final Gray8Image imBlue) throws ImageError {
        if ((imRed.getWidth() != imGreen.getWidth()) || (imGreen.getWidth() != imBlue.getWidth()) || (imRed.getHeight() != imGreen.getHeight()) || (imGreen.getHeight() != imBlue.getHeight())) {
            throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.IMAGE_SIZES_DIFFER, imRed.toString(), imGreen.toString(), imBlue.toString());
        }
        final RgbImage rgb = new RgbImage<>(imRed.getWidth(), imRed.getHeight());
        final Byte[] redData = imRed.getData();
        final Byte[] greenData = imGreen.getData();
        final Byte[] blueData = imBlue.getData();
        final Integer[] rgbData = rgb.getData();
        for (int i = 0; i < (imRed.getWidth() * imRed.getHeight()); i++) {
            /*
             * Convert from signed byte value to unsigned byte for storage in
             * the RGB image.
             */
            final int redUnsigned = (redData[i]) - Byte.MIN_VALUE;
            final int greenUnsigned = (greenData[i]) - Byte.MIN_VALUE;
            final int blueUnsigned = (blueData[i]) - Byte.MIN_VALUE;
            /* Create ARGB word */
            rgbData[i] = (0xFF000000) | // mask is off
                    ((redUnsigned) << 16) | ((greenUnsigned) << 8) | blueUnsigned;
        }
        return rgb;
    }
}