/*
* RgbSubSample.java
*
* Created on September 2, 2006, 3:59 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.Image;
import jjil.core.PipelineStage;
import jjil.core.RgbImage;
/**
* Pipeline stage reduces an RgbImage's size by subsampling WITHOUT
* smoothing. This results in an aliased image but can be
* done very quickly and the artifacts resulting from the subsampling can
* themselves be useful for detection of certain kinds of objects such
* as barcodes. This pipeline stage should be used with caution because
* of the artifacts introduced by subsampling without smoothing.
*
* @author webb
*/
public class RgbSubSample extends PipelineStage {
private int cTargetHeight;
private int cTargetWidth;
/**
* Creates a new instance of RgbSubSample.
* @param cTargetWidth the new width
* @param cTargetHeight the new height
* @throws jjil.core.Error if the target width or height is less than or equal to zero.
*/
public RgbSubSample(int cTargetWidth, int cTargetHeight)
throws jjil.core.Error {
setTargetSize(cTargetWidth, cTargetHeight);
}
/** Reduces an RgbImage by a factor horizontally and vertically through
* averaging. The reduction factor must be an even multiple of the image
* size.
*
* @param image the input image.
* @throws jjil.core.Error if the input image is not gray, or
* the reduction factor does not evenly divide the image size.
*/
public void push(Image image) throws jjil.core.Error {
if (!(image instanceof RgbImage)) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.IMAGE_NOT_RGBIMAGE,
image.toString(),
null,
null);
}
if (image.getWidth() < this.cTargetWidth) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.SHRINK_OUTPUT_LARGER_THAN_INPUT,
image.toString(),
this.toString(),
null);
}
if (image.getHeight() < this.cTargetHeight) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.SHRINK_OUTPUT_LARGER_THAN_INPUT,
image.toString(),
this.toString(),
null);
}
// note that Java division truncates. So
// e.g. cReduceWidth * this.cTargetWidth <= image.getWidth
// This is important in the for loop below to keep from out of bounds
// array access.
int cReduceWidth = image.getWidth() / this.cTargetWidth;
int cReduceHeight = image.getHeight() / this.cTargetHeight;
RgbImage rgb = (RgbImage) image;
int[] rnIn = rgb.getData();
RgbImage result = new RgbImage(
this.cTargetWidth,
this.cTargetHeight);
int[] rnOut = result.getData();
for (int i=0; i<this.cTargetHeight; i++) {
for (int j=0; j<this.cTargetWidth; j++) {
rnOut[i*this.cTargetWidth + j] =
rnIn[(i*image.getWidth()*cReduceHeight) + (j*cReduceWidth)];
}
}
super.setOutput(result);
}
/** Returns the target height.
*
* @return the target height.
*/
public int getTargetHeight()
{
return this.cTargetHeight;
}
/** Returns the target width.
*
* @return the target width.
*/
public int getTargetWidth()
{
return this.cTargetWidth;
}
/** Sets a new width, height target size.
*
* @param cTargetWidth the target image width.
* @param cTargetHeight the target image height.
* @throws jjil.core.Error if either cTargetWidth or cTargetHeight
* is less than or equal to 0.
*/
public void setTargetSize(int cTargetWidth, int cTargetHeight)
throws jjil.core.Error {
if (cTargetWidth <= 0 || cTargetHeight <= 0) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.OUTPUT_IMAGE_SIZE_NEGATIVE,
new Integer(cTargetWidth).toString(),
new Integer(cTargetHeight).toString(),
null);
}
this.cTargetWidth = cTargetWidth;
this.cTargetHeight = cTargetHeight;
}
/** Return a string describing the reduction operation.
*
* @return the string describing the reduction operation.
*/
public String toString() {
return super.toString() + " (" + this.cTargetWidth + "," + //$NON-NLS-1$ //$NON-NLS-2$
this.cTargetHeight + ")"; //$NON-NLS-1$
}
}