/*
* 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 <http://www.gnu.org/licenses/>.
*
*/
package jjil.algorithm;
import jjil.core.Error;
import jjil.core.Gray32Image;
import jjil.core.Gray8Image;
import jjil.core.Image;
import jjil.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 jjil.core.Error if either is less than or equal to zero.
*/
public Gray8Shrink(int cWidth, int cHeight)
throws jjil.core.Error {
setWidth(cWidth);
setHeight(cHeight);
}
/** Gets current target height
*
* @return current height
*/
public int getHeight() {
return this.cHeight;
}
/** Gets current target width
*
* @return current width
*/
public int getWidth() {
return this.cWidth;
}
/**
* Process an input Gray8Image, producing a new shrunk output image.
* @param image The input Gray8Image.
* @throws jjil.core.Error if input is not a Gray8Image, or the input image size is smaller (either
* horizontally or vertically) than the desired size.
*/
public void push(Image image) throws jjil.core.Error {
if (!(image instanceof Gray8Image)) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.IMAGE_NOT_GRAY8IMAGE,
image.toString(),
null,
null);
}
if (image.getWidth() < this.cWidth || image.getHeight() < this.cHeight) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.SHRINK_OUTPUT_LARGER_THAN_INPUT,
image.toString(),
this.toString(),
null);
}
Gray8Image input = (Gray8Image) image;
/* horizontal shrink */
Gray32Image horiz = shrinkHoriz(input);
/* vertical shrink */
Gray8Image result = shrinkVert(horiz);
super.setOutput(result);
}
/** Changes target height
*
* @param cHeight the new target height.
* @throws jjil.core.Error if height is not positive
*/
public void setHeight(int cHeight) throws jjil.core.Error {
if (cHeight <= 0) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.OUTPUT_IMAGE_SIZE_NEGATIVE,
new Integer(cHeight).toString(),
this.toString(),
null);
}
this.cHeight = cHeight;
}
/** Changes target width
*
* @param cWidth the new target width.
* @throws jjil.core.Error if height is not positive
*/
public void setWidth(int cWidth) throws jjil.core.Error {
if (cWidth <= 0) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.OUTPUT_IMAGE_SIZE_NEGATIVE,
new Integer(cWidth).toString(),
this.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(Gray8Image input) {
/* horizontal shrink */
Gray32Image horiz = new Gray32Image(this.cWidth, input.getHeight());
byte[] inData = input.getData();
int[] outData = horiz.getData();
int[] nPixelSum = new int[input.getHeight()];
for (int i=0; i<input.getHeight(); i++) {
nPixelSum[i] = 0;
}
int nPos = 0;
int nNextPos = input.getWidth() * 256 / this.cWidth;
int nCount = 0;
for (int j=0; j<input.getWidth() && nPos < this.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*this.cWidth + nPos] = nPixelSum[i] * 256 / nCount;
nPixelSum[i] = 0;
}
nPos += 1;
nNextPos += input.getWidth() * 256 / this.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(Gray32Image input) {
/* vertical shrink */
Gray8Image vert = new Gray8Image(input.getWidth(), this.cHeight);
int[] inData = input.getData();
byte[] outData = vert.getData();
int[] nPixelSum = new int[input.getWidth()];
for (int i=0; i<input.getWidth(); i++) {
nPixelSum[i] = 0;
}
int nPos = 0;
int nNextPos = input.getHeight() * 256 / this.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 >= this.cHeight) {
break;
}
nNextPos += input.getHeight() * 256 / this.cHeight;
nCount = 0;
}
}
return vert;
}
/** Return a string describing the shrinking operation.
*
* @return the string describing the shrinking operation.
*/
public String toString() {
return super.toString() + " (" + this.cWidth + "," + this.cHeight + ")"; //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
}
}