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/*
 * RgbSubSample.java
 *
 * Created on September 2, 2006, 3:59 PM
 *
 * 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.Image;
import com.github.ojil.core.ImageError;
import com.github.ojil.core.PipelineStage;
import com.github.ojil.core.RgbImage;

/**
 * Pipeline stage reduces an RgbImage's size by subsampling WITHOUT smoothing.
 * This results in an aliased image but can be done very quickly and the
 * artifacts resulting from the subsampling can themselves be useful for
 * detection of certain kinds of objects such as barcodes. This pipeline stage
 * should be used with caution because of the artifacts introduced by
 * subsampling without smoothing.
 *
 * @author webb
 */
public class RgbSubSample extends PipelineStage {
    private int cTargetHeight;
    private int cTargetWidth;
    
    /**
     * Creates a new instance of RgbSubSample.
     * 
     * @param cTargetWidth
     *            the new width
     * @param cTargetHeight
     *            the new height
     * @throws ImageError
     *             if the target width or height is less than or equal to zero.
     */
    public RgbSubSample(final int cTargetWidth, final int cTargetHeight) throws ImageError {
        setTargetSize(cTargetWidth, cTargetHeight);
    }
    
    /**
     * Reduces an RgbImage by a factor horizontally and vertically through
     * averaging. The reduction factor must be an even multiple of the image
     * size.
     *
     * @param image
     *            the input image.
     * @throws ImageError
     *             if the input image is not gray, or the reduction factor does
     *             not evenly divide the image size.
     */
    @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);
        }
        if (image.getWidth() < cTargetWidth) {
            throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.SHRINK_OUTPUT_LARGER_THAN_INPUT, image.toString(), toString(), null);
        }
        if (image.getHeight() < cTargetHeight) {
            throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.SHRINK_OUTPUT_LARGER_THAN_INPUT, image.toString(), toString(), null);
        }
        // note that Java division truncates. So
        // e.g. cReduceWidth * this.cTargetWidth <= image.getWidth
        // This is important in the for loop below to keep from out of bounds
        // array access.
        final int cReduceWidth = image.getWidth() / cTargetWidth;
        final int cReduceHeight = image.getHeight() / cTargetHeight;
        final RgbImage rgb = (RgbImage) image;
        final Integer[] rnIn = rgb.getData();
        final RgbImage result = new RgbImage<>(cTargetWidth, cTargetHeight);
        final Integer[] rnOut = result.getData();
        for (int i = 0; i < cTargetHeight; i++) {
            for (int j = 0; j < cTargetWidth; j++) {
                rnOut[(i * cTargetWidth) + j] = rnIn[(i * image.getWidth() * cReduceHeight) + (j * cReduceWidth)];
            }
        }
        super.setOutput(result);
    }
    
    /**
     * Returns the target height.
     *
     * @return the target height.
     */
    public int getTargetHeight() {
        return cTargetHeight;
    }
    
    /**
     * Returns the target width.
     *
     * @return the target width.
     */
    public int getTargetWidth() {
        return cTargetWidth;
    }
    
    /**
     * Sets a new width, height target size.
     *
     * @param cTargetWidth
     *            the target image width.
     * @param cTargetHeight
     *            the target image height.
     * @throws ImageError
     *             if either cTargetWidth or cTargetHeight is less than or equal
     *             to 0.
     */
    public void setTargetSize(final int cTargetWidth, final int cTargetHeight) throws ImageError {
        if ((cTargetWidth <= 0) || (cTargetHeight <= 0)) {
            throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.OUTPUT_IMAGE_SIZE_NEGATIVE, new Integer(cTargetWidth).toString(), new Integer(cTargetHeight).toString(), null);
        }
        this.cTargetWidth = cTargetWidth;
        this.cTargetHeight = cTargetHeight;
    }
    
    /**
     * Return a string describing the reduction operation.
     *
     * @return the string describing the reduction operation.
     */
    @Override
    public String toString() {
        return super.toString() + " (" + cTargetWidth + "," + //$NON-NLS-1$ //$NON-NLS-2$
                cTargetHeight + ")"; //$NON-NLS-1$
    }
}