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/*
 * Gray8Fft.java
 *
 * Created on October 31, 2007, 4:02 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.Complex;
import com.github.ojil.core.Complex32Image;
import com.github.ojil.core.Error;
import com.github.ojil.core.Gray8Image;
import com.github.ojil.core.Image;
import com.github.ojil.core.PipelineStage;

/**
 * Takes the fast Fourier transform of the input Gray8Image. The output image
 * is a Complex32Image. The image size must be a power of 2.
 * @author webb
 */
public class Gray8Fft extends PipelineStage {
    /**
     * Defines the scale factor applied to the image as a power of two, for accuracy.
     */
    public static int SCALE = 8;
    
    private Fft1d fft = null;
    
    /**
     * Creates a new instance of Gray8Fft.
     */
    public Gray8Fft() {
    }
    
    /**
     * Performs the fast Fourier transform on an image. The input image is a Gray8Image,
     * and the output is a Complex32Image. The input is scaled by shifting left SCALE
     * bits before the transformation, for accuracy.
     * @param im Input image. Must be a Gray8Image.
     * @throws com.github.ojil.core.Error if the input is not a Gray8Image or is not a power of two in width and 
     * height.
     */
    public void push(Image im) throws com.github.ojil.core.Error {
        if (!(im instanceof Gray8Image)) {
            throw new Error(
            				Error.PACKAGE.ALGORITHM,
            				ErrorCodes.IMAGE_NOT_GRAY8IMAGE,
            				im.toString(),
            				null,
            				null);
        }
        int nWidth = im.getWidth();
        int nHeight = im.getHeight();
        if ((nWidth & (nWidth-1)) != 0) {
            throw new Error(
            				Error.PACKAGE.ALGORITHM,
            				ErrorCodes.FFT_SIZE_NOT_POWER_OF_2,
            				im.toString(),
            				null,
            				null);
        }
        if ((nHeight & (nHeight-1)) != 0) {
            throw new Error(
            				Error.PACKAGE.ALGORITHM,
            				ErrorCodes.FFT_SIZE_NOT_POWER_OF_2,
            				im.toString(),
            				null,
            				null);
        }
        // initialize FFT
        if (this.fft == null) {
            this.fft = new Fft1d(Math.max(nWidth, nHeight));
        } else {
            this.fft.setMaxWidth(Math.max(nWidth, nHeight));
        }
        
        Gray8Image gray = (Gray8Image) im;
        Byte data[] = gray.getData();
        // create output
        Complex32Image cxmResult = new Complex32Image(nWidth, nHeight);
        // take FFT of each row
        int nIndex = 0;
        Complex cxRow[] = new Complex[nWidth];
        for (int i=0; i