/*
* MaskedGray8SubImgGen.java
*
* Given a target image size and a horizontal and vertical offset
* generates a series of subimages within the input image,
* each subimage offset by an integral multiple of the
* offset with size equal to the target size and lying
* entirely within the original image. The offset of the
* subimage in the input image is given in the subimage class.
* In this masked version only subimages whose center is not a masked
* point (mask image value = 0) will be generated.
*
* Created on July 1, 2007, 1:51 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.Gray8MaskedImage;
import jjil.core.Gray8OffsetImage;
import jjil.core.Image;
import jjil.core.PipelineStage;
/**
* Generates subimages from a source Gray8Image, using a mask. In a normal
* subimage generator subimages are generated evenly spaced across the input
* image. Here, the subimage is generated only if is center point is not masked.
* This can increase processing speed in hierarchical detection operations since features
* detected at coarser resolution don't have to be redetected at finer resolution.
* @author webb
*/
public class MaskedGray8SubImgGen extends PipelineStage {
Gray8MaskedImage imageInput; // input image
boolean oSubImageReady; // true if sub image position is OK
int nHeight; // target height
int nHorizLimit = 0; // number of subimages generated horizontally
int nVertLimit = 0; // number of subimages generated vertically
int nHorizIndex = 0; // current subimiage index, horizontal
int nVertIndex = 0; // current subimage index, vertical
int nWidth; // target width
int nXOffset; // x offset multiple for subimages
int nYOffset; // y offset multiple for subimages
/**
* Creates a new instance of MaskedGray8SubImgGen.
* @param nWidth the width of the generated subimage.
* @param nHeight the height of the generated subimage.
* @param nXOffset the horizontal offset between subimages.
* @param nYOffset the vertical offset between subimages.
*/
public MaskedGray8SubImgGen(int nWidth, int nHeight, int nXOffset, int nYOffset) {
this.nWidth = nWidth;
this.nHeight = nHeight;
this.nXOffset = nXOffset;
this.nYOffset = nYOffset;
this.oSubImageReady = false;
// create an output image. We'll reuse this
// image, changing the contents and offset,
// for every Gray8OffsetImage we output.
super.imageOutput = new Gray8OffsetImage(
this.nWidth,
this.nHeight,
0,
0);
}
/** advanceToNextSubImage advances to the next position for generating
* a subimage. It returns true iff there is a non-masked position within
* the image where a subimage can be generated.
*/
private boolean advanceToNextSubImage() {
if (oSubImageReady) {
return this.nVertIndex <= this.nVertLimit;
}
// advance to next subimage position
this.nHorizIndex ++;
if (this.nHorizIndex > this.nHorizLimit) {
this.nVertIndex ++;
this.nHorizIndex = 0;
}
// nPos is the byte address that we will test in the mask image
// to see if it is OK to generate a subimage. It is the midpoint
// of the subimage.
int nPos = (this.nHeight / 2 +
this.nVertIndex * this.nYOffset) * this.imageInput.getWidth() +
this.nWidth / 2 + this.nHorizIndex * this.nXOffset;
// starting at the current position, search forward for a position
// that is not masked.
while (this.nVertIndex <= this.nVertLimit) {
while (this.nHorizIndex <= this.nHorizLimit) {
if (this.imageInput.getMaskData()[nPos] == Byte.MIN_VALUE) {
// found it
oSubImageReady = true;
return true;
}
this.nHorizIndex ++;
nPos += this.nWidth;
}
this.nHorizIndex = 0;
this.nVertIndex ++;
// reset nPos for next row of subimages
nPos = (this.nHeight / 2 +
this.nVertIndex * this.nYOffset) * this.imageInput.getWidth() +
this.nWidth / 2;
}
this.oSubImageReady = true;
return false;
}
// We are done producing images when the advance returns no more images
/**
* Returns true iff there is another image available from getFront().
* Note that the existence of another image from
* MaskedGray8SubImgGen depends on the mask image so there's no way to guarantee
* there will be even one subimage generated for a particular input. You must
* always call isEmpty().
* @return true iff there is another image available from getFront().
*/
public boolean isEmpty() {
return !advanceToNextSubImage();
}
// Return the next subimage and increment the indices
/**
* Returns the next subimage generated. The subimage will have its offset
* set to indicate where it was generated in the input image.
* @return a MaskedGray8SubImage that is the next subimage in the input Gray8Image to
* be processed.
* @throws jjil.core.Error if no subimage is available (you have to call isEmpty() to determine if
* a subimage is available. As few as 0 subimage can be generated for a
* given input if the entire image is masked.) Also throws if the output
* image (stored in the superclass) has been changed in type.
*/
public Image getFront() throws jjil.core.Error
{
// reuse output image
// check to make sure nobody damaged it somehow
if (!(super.imageOutput instanceof Gray8OffsetImage)) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.OBJECT_NOT_EXPECTED_TYPE,
imageOutput.toString(),
"Gray8SubImage",
null);
}
if (!advanceToNextSubImage()) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.SUBIMAGE_NO_IMAGE_AVAILABLE,
this.toString(),
null,
null);
}
byte[] dataIn = this.imageInput.getData();
// offset of first pixel of the subimage within the
// larget image.
int nHOffset = this.nXOffset * this.nHorizIndex;
int nVOffset = this.nYOffset * this.nVertIndex;
Gray8OffsetImage imageResult = (Gray8OffsetImage) super.imageOutput;
imageResult.setXOffset(nHOffset);
imageResult.setYOffset(nVOffset);
byte[] dataOut = imageResult.getData();
// don't access outside the image
int nLimitY = Math.min(this.imageInput.getHeight() - nVOffset, this.nHeight);
int nLimitX = Math.min(this.imageInput.getWidth() - nHOffset, this.nWidth);
for (int i=0; i<nLimitY; i++) {
int nVInLoc = i + nVOffset;
System.arraycopy(
dataIn,
nVInLoc*this.imageInput.getWidth() + nHOffset,
dataOut,
i*this.nWidth,
nLimitX);
}
this.oSubImageReady = false;
return imageResult;
}
/**
* Accepts a new MaskedGray8Image and initializes all the generator indices.
* @param image The input MaskedGray8Image.
* @throws jjil.core.Error if the input is not of type MaskedGray8Image or is smaller than the
* subimages to be generated.
*/
public void push(Image image) throws jjil.core.Error {
if (!(image instanceof Gray8MaskedImage)) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.OBJECT_NOT_EXPECTED_TYPE,
image.toString(),
"Gray8MaskedImage",
null);
}
if (image.getWidth() < this.nWidth || image.getHeight() < this.nHeight) {
throw new Error(
Error.PACKAGE.ALGORITHM,
ErrorCodes.IMAGE_TOO_SMALL,
image.toString(),
new Integer(this.nWidth).toString(),
new Integer(this.nHeight).toString());
}
this.imageInput = (Gray8MaskedImage) image;
// we want to find the largest integer l such that
// (l-1) * w + w <= iw
// where l = computed limit on index
// w = subimage width or height
// iw = image width or height
// or l = (iw - w) / w + 1 (truncated)
// Java division truncates
this.nHorizLimit = (image.getWidth() - this.nWidth) / this.nXOffset;
this.nVertLimit = (image.getHeight() - this.nHeight) / this.nYOffset;
this.nHorizIndex = -1; // first time through increments
this.nVertIndex = 0;
this.oSubImageReady = false;
}
}