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/*
 * Gray8RectStretch.java
 *
 * Created on September 9, 2006, 8:08 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.Image;
import com.github.ojil.core.ImageError;
import com.github.ojil.core.PipelineStage;

/**
 * Pipeline stage stretches an image to a larger rectangular size with bilinear
 * interpolation. For more information on this and other image warps, see George
 * Wolberg's excellent book, "Digital Image Warping", Wiley-IEEE Computer
 * Society Press, 1990.
 * 
 * @author webb
 */
public class Gray8RectStretch extends PipelineStage {
    private int cHeight;
    private int cWidth;
    
    /**
     * Creates a new instance of Gray8RectStretch.
     *
     * @param cWidth
     *            new image width
     * @param cHeight
     *            new image height
     * @throws ImageError
     *             if either is less than or equal to zero.
     */
    public Gray8RectStretch(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;
    }
    
    /**
     * Bilinear interpolation to stretch image to (cWidth, cHeight). Does this
     * in two passes, for more efficient computation.
     * 
     * @param image
     *            the input image
     * @throws ImageError
     *             if input image is not gray 8 bits, or the input image size is
     *             larger than the target size. This class does not do
     *             subsampling, only interpolation.
     */
    @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.STRETCH_OUTPUT_SMALLER_THAN_INPUT, image.toString(), new Integer(cWidth).toString(), new Integer(cHeight).toString());
        }
        final Gray8Image input = (Gray8Image) image;
        /**
         * we do the stretch in to passes, one horizontal and the other
         * vertical. This leads to less computation than doing it in one pass,
         * because the calculation of the interpolation weights has to happen
         * only once.
         */
        /* horizontal stretch */
        final Gray8Image horiz = stretchHoriz(input);
        final Gray8Image result = stretchVert(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(), null, 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(), null, null);
        }
        this.cWidth = cWidth;
    }
    
    /**
     * Horizontal stretch. Stretches the input from
     * (input.getWidth(),input.getHeight()) to (this.cWidth,input.getHeight())
     *
     * @param input
     *            the input image
     * @return the stretched image
     */
    private Gray8Image stretchHoriz(final Gray8Image input) {
        /* horizontal stretch */
        final Gray8Image horiz = new Gray8Image<>(cWidth, input.getHeight());
        final Byte[] inData = input.getData();
        final Byte[] outData = horiz.getData();
        for (int j = 0; j < cWidth; j++) {
            /*
             * the interpolated position is j*input.getWidth()/this.cWidth.
             * Compute the remainder of this division.
             */
            final int cMod = (j * input.getWidth()) % cWidth;
            /* compute the left integral pixel position */
            int cX = ((j * input.getWidth()) - cMod) / cWidth;
            if (cX < (input.getWidth() - 1)) {
                /*
                 * compute the fractional position in that pixel (* 256 so the
                 * computation can be done in integer
                 */
                final int cFrac = (cMod << 8) / cWidth;
                for (int i = 0; i < input.getHeight(); i++) {
                    /* interpolate */
                    outData[(i * cWidth) + j] = (byte) (((inData[(i * input.getWidth()) + cX] * (256 - cFrac)) + (inData[(i * input.getWidth()) + cX + 1] * cFrac)) >> 8);
                }
            } else {
                /*
                 * adjust cX so we will use the last column of the input image
                 * for interpolating beyond its right edge, without accessing a
                 * value outside the array bounds. In other words, for
                 * fractional input positions beyond input.getWidth()-1 we use
                 * input.getWidth()-1 as the column.
                 */
                cX = input.getWidth() - 2;
                for (int i = 0; i < input.getHeight(); i++) {
                    /* interpolate */
                    outData[(i * cWidth) + j] = inData[(i * input.getWidth()) + cX + 1];
                }
            }
        }
        return horiz;
    }
    
    /**
     * Vertical stretch. Stretches an image from (this.cWidth,input.getHeight())
     * to (this.cWidth,this.cHeight)
     *
     * @param input
     *            the input image.
     * @returns the stretched image.
     */
    private Gray8Image stretchVert(final Gray8Image input) {
        final Byte[] inData = input.getData();
        final Gray8Image vert = new Gray8Image<>(cWidth, cHeight);
        final Byte[] outData = vert.getData();
        for (int i = 0; i < cHeight; i++) {
            /* remainder */
            final int cMod = (i * input.getHeight()) % cHeight;
            /* top integral position */
            int cY = ((i * input.getHeight()) - cMod) / cHeight;
            if (cY < (input.getHeight() - 1)) {
                /* fractional position, times 256 */
                final int cFrac = (cMod << 8) / cHeight;
                for (int j = 0; j < input.getWidth(); j++) {
                    /* interpolate */
                    outData[(i * cWidth) + j] = (byte) (((inData[(cY * cWidth) + j] * (256 - cFrac)) + (inData[((cY + 1) * cWidth) + j] * cFrac)) >> 8);
                }
            } else {
                /*
                 * adjust cX so we will use the last row of the input image for
                 * interpolating beyond its bottom edge, without accessing a
                 * value outside the array bounds. In other words, for
                 * fractional input positions beyond input.getHeight()-1 we use
                 * input.getHeight()-1 as the row.
                 */
                cY = input.getHeight() - 2;
                for (int j = 0; j < input.getWidth(); j++) {
                    /* interpolate */
                    outData[(i * cWidth) + j] = (inData[((cY + 1) * cWidth) + j]);
                }
            }
        }
        return vert;
    }
    
    /**
     * Return a string describing the stretching operation.
     *
     * @return the string describing the stretching operation.
     */
    @Override
    public String toString() {
        return super.toString() + " (" + cWidth + "," + cHeight + ")"; //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
    }
}