/*
* Complex32IFft.java
*
* Created on October 31, 2007, 5:02 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 <http://www.gnu.org/licenses/>.
*
*/
package jjil.algorithm;
import jjil.core.Complex;
import jjil.core.Complex32Image;
import jjil.core.Error;
import jjil.core.Gray32Image;
import jjil.core.Gray8Image;
import jjil.core.Image;
import jjil.core.PipelineStage;
/**
* Computes the inverse FFT of the input Complex32Image. The output is a Gray8Image,
* which is the magnitude of the inverse FFT. The output can be scaled so the
* maximum and minimum values of the magnitude are mapped to Byte.MAX_VALUE and
* Byte.MIN_VALUE.
* @author webb
*/
public class Complex32IFft extends PipelineStage {
private boolean bScale;
private Fft1d fft = null;
/**
* Creates a new instance of Complex32IFft
* @param bScale Whether or not to scale the output before converting it to a byte.
*/
public Complex32IFft(boolean bScale) {
this.bScale = bScale;
}
/**
* Perform the inverse FFT on the input Complex32Image, producing a Gray8Image.
* @param im Input image. Must be a power of 2 in size and of type Complex32Image.
* @throws jjil.core.Error if the input is not a power of 2 in size or not a Complex32Image.
*/
public void push(Image im) throws jjil.core.Error {
if (!(im instanceof Complex32Image)) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.IMAGE_NOT_COMPLEX32IMAGE,
im.toString(),
null,
null);
}
// make sure the image width and height are powers of two
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));
}
// get access to the complex image
Complex32Image cxmIn = (Complex32Image) im;
Complex data[] = cxmIn.getData();
// create output
Complex32Image cxmResult = new Complex32Image(nWidth, nHeight);
// take inverse FFT of each row
Complex cxRow[] = new Complex[nWidth];
for (int i=0; i<nHeight; i++) {
System.arraycopy(data, i*nWidth, cxRow, 0, nWidth);
// compute inverse FFT
Complex cxResult[] = this.fft.ifft(cxRow);
// save result
System.arraycopy(cxResult, 0, cxmResult.getData(), i*nWidth, nWidth);
}
// take inverse FFT of each column
Complex cxCol[] = new Complex[nHeight];
for (int j=0; j<nWidth; j++) {
// copy column into a 1-D array
for (int i=0; i<nHeight; i++) {
cxCol[i] = cxmResult.getData()[i*nWidth+j];
}
// compute inverse FFT
Complex cxResult[] = this.fft.ifft(cxCol);
// save result back into column
for (int i=0; i<nHeight; i++) {
cxmResult.getData()[i*nWidth+j] = cxResult[i];
}
}
// convert back to a gray image
// first convert it to an integer image
Gray32Image imInteger = new Gray32Image(nWidth, nHeight);
Complex cxData[] = cxmResult.getData();
int nData[] = imInteger.getData();
int nMinVal = Integer.MAX_VALUE;
int nMaxVal = Integer.MIN_VALUE;
for (int i = 0; i < nWidth * nHeight; i++) {
// magnitude is always guaranteed to be >= 0 so we only have to clamp
// below Byte.MAX_VALUE
nData[i] = cxData[i].rsh(Gray8Fft.SCALE).magnitude();
if (this.bScale) {
nMinVal = Math.min(nMinVal, nData[i]);
nMaxVal = Math.max(nMaxVal, nData[i]);
}
}
// compute range of values in image and avoid division by 0 later
int nDiff = Math.max(nMaxVal - nMinVal, 1);
// this inverts the operation in Gray8Fft. The two must be kept in sync.
Gray8Image imResult = new Gray8Image(nWidth, nHeight);
byte bData[] = imResult.getData();
if (bScale) {
for (int i = 0; i < nWidth * nHeight; i++) {
// magnitude is always guaranteed to be >= 0 so we only have to clamp
// below Byte.MAX_VALUE
bData[i] = (byte)
(((nData[i] - nMinVal) * (Byte.MAX_VALUE - Byte.MIN_VALUE)) /
nDiff + Byte.MIN_VALUE);
}
} else {
for (int i = 0; i < nWidth * nHeight; i++) {
// magnitude is always guaranteed to be >= 0 so we only have to clamp
// below Byte.MAX_VALUE
bData[i] = (byte) Math.min(Byte.MAX_VALUE, nData[i] + Byte.MIN_VALUE);
}
}
super.setOutput(imResult);
}
}