com.github.ojil.algorithm.Gray8Shrink Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of ojil-core Show documentation
Open Java Imaging Library.
There is a newer version: 0.0.11
/*
 * Gray8Shrink.java.
 *    Reduces an image to a new size by averaging the pixels nearest each
 * target pixel's pre-image. This is done in two passes, first averaging
 * horizontally and then vertically. The horizontal average is done with the
 * pixel values shifted 8 bits for accuracy.
 *
 * Created on October 13, 2007, 2:21 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.Gray32Image;
import com.github.ojil.core.Gray8Image;
import com.github.ojil.core.Image;
import com.github.ojil.core.ImageError;
import com.github.ojil.core.PipelineStage;

/**
 * Shrinks an input Gray8Image to a given new size. The shrinking is done with
 * proper averaging so each output pixel is the average of the corresponding
 * rectangular region in the input.
 * 
 * @author webb
 */
public class Gray8Shrink extends PipelineStage {
    private int cHeight;
    private int cWidth;
    
    /**
     * Creates a new instance of GrayRectStretch.
     *
     * @param cWidth
     *            new image width
     * @param cHeight
     *            new image height
     * @throws ImageError
     *             if either is less than or equal to zero.
     */
    public Gray8Shrink(final int cWidth, final int cHeight) throws ImageError {
        setWidth(cWidth);
        setHeight(cHeight);
    }
    
    /**
     * Gets current target height
     *
     * @return current height
     */
    public int getHeight() {
        return cHeight;
    }
    
    /**
     * Gets current target width
     *
     * @return current width
     */
    public int getWidth() {
        return cWidth;
    }
    
    /**
     * Process an input Gray8Image, producing a new shrunk output image.
     * 
     * @param image
     *            The input Gray8Image.
     * @throws ImageError
     *             if input is not a Gray8Image, or the input image size is
     *             smaller (either horizontally or vertically) than the desired
     *             size.
     */
    @Override
    public void push(final Image image) throws ImageError {
        if (!(image instanceof Gray8Image)) {
            throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.IMAGE_NOT_GRAY8IMAGE, image.toString(), null, null);
        }
        if ((image.getWidth() < cWidth) || (image.getHeight() < cHeight)) {
            throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.SHRINK_OUTPUT_LARGER_THAN_INPUT, image.toString(), toString(), null);
        }
        final Gray8Image input = (Gray8Image) image;
        /* horizontal shrink */
        final Gray32Image horiz = shrinkHoriz(input);
        /* vertical shrink */
        final Gray8Image result = shrinkVert(horiz);
        super.setOutput(result);
    }
    
    /**
     * Changes target height
     * 
     * @param cHeight
     *            the new target height.
     * @throws ImageError
     *             if height is not positive
     */
    public void setHeight(final int cHeight) throws ImageError {
        if (cHeight <= 0) {
            throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.OUTPUT_IMAGE_SIZE_NEGATIVE, new Integer(cHeight).toString(), toString(), null);
        }
        this.cHeight = cHeight;
    }
    
    /**
     * Changes target width
     * 
     * @param cWidth
     *            the new target width.
     * @throws ImageError
     *             if height is not positive
     */
    public void setWidth(final int cWidth) throws ImageError {
        if (cWidth <= 0) {
            throw new ImageError(ImageError.PACKAGE.ALGORITHM, AlgorithmErrorCodes.OUTPUT_IMAGE_SIZE_NEGATIVE, new Integer(cWidth).toString(), toString(), null);
        }
        this.cWidth = cWidth;
    }
    
    /**
     * Horizontal shrink. Shrinks the input from
     * (input.getWidth(),input.getHeight()) to (this.cWidth,input.getHeight())
     * by averaging the pixels that are nearest each target pixel's pre-image.
     * The mapping is x -> x * this.cWidth / input.getWidth() or in inverse y ->
     * y * input.getWidth() / this.cWidth
     *
     * @param input
     *            the input image
     * @return the shrunk image
     */
    private Gray32Image shrinkHoriz(final Gray8Image input) {
        /* horizontal shrink */
        final Gray32Image horiz = new Gray32Image<>(cWidth, input.getHeight());
        final Byte[] inData = input.getData();
        final Integer[] outData = horiz.getData();
        final Integer[] nPixelSum = new Integer[input.getHeight()];
        for (int i = 0; i < input.getHeight(); i++) {
            nPixelSum[i] = 0;
        }
        int nPos = 0;
        int nNextPos = (input.getWidth() * 256) / cWidth;
        int nCount = 0;
        for (int j = 0; (j < input.getWidth()) && (nPos < cWidth); j++) {
            for (int i = 0; i < input.getHeight(); i++) {
                nPixelSum[i] += inData[(i * input.getWidth()) + j] - Byte.MIN_VALUE;
            }
            nCount += 1;
            if (((j + 1) * 256) >= nNextPos) {
                for (int i = 0; i < input.getHeight(); i++) {
                    outData[(i * cWidth) + nPos] = (nPixelSum[i] * 256) / nCount;
                    nPixelSum[i] = 0;
                }
                nPos += 1;
                nNextPos += (input.getWidth() * 256) / cWidth;
                nCount = 0;
            }
        }
        return horiz;
    }
    
    /**
     * Vertical shrink. Shrinks an image from (this.cWidth,input.getHeight()) to
     * (this.cWidth,this.cHeight) by averaging the pixels that are nearest each
     * target pixel's pre-image. The mapping is x -> x * this.cHeight /
     * input.getHeight() or in inverse y -> y * input.getHeight() / this.cHeight
     *
     * @param input
     *            the input image.
     * @returns the shrunk image.
     */
    private Gray8Image shrinkVert(final Gray32Image input) {
        /* vertical shrink */
        final Gray8Image vert = new Gray8Image<>(input.getWidth(), cHeight);
        final Integer[] inData = input.getData();
        final Byte[] outData = vert.getData();
        final Integer[] nPixelSum = new Integer[input.getWidth()];
        for (int i = 0; i < input.getWidth(); i++) {
            nPixelSum[i] = 0;
        }
        int nPos = 0;
        int nNextPos = (input.getHeight() * 256) / cHeight;
        int nCount = 0;
        for (int j = 0; (j < input.getHeight()) && (nPos < input.getHeight()); j++) {
            for (int i = 0; i < input.getWidth(); i++) {
                nPixelSum[i] += inData[(j * input.getWidth()) + i];
            }
            nCount += 1;
            if (((j + 1) * 256) >= nNextPos) {
                for (int i = 0; i < input.getWidth(); i++) {
                    outData[(nPos * input.getWidth()) + i] = (byte) ((nPixelSum[i] / nCount / 256) + Byte.MIN_VALUE);
                    nPixelSum[i] = 0;
                }
                nPos += 1;
                if (nPos >= cHeight) {
                    break;
                }
                nNextPos += (input.getHeight() * 256) / cHeight;
                nCount = 0;
            }
        }
        return vert;
    }
    
    /**
     * Return a string describing the shrinking operation.
     *
     * @return the string describing the shrinking operation.
     */
    @Override
    public String toString() {
        return super.toString() + " (" + cWidth + "," + cHeight + ")"; //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
    }
}