/*
* Copyright 2013 Alibaba.com All right reserved. This software is the
* confidential and proprietary information of Alibaba.com ("Confidential
* Information"). You shall not disclose such Confidential Information and shall
* use it only in accordance with the terms of the license agreement you entered
* into with Alibaba.com.
*/
package com.alibaba.security.simpleimage.analyze.sift.conv;
import com.alibaba.security.simpleimage.analyze.sift.ImageMap;
/**
* 类ConvoLutionFilter.java的实现描述：TODO 类实现描述
*
* @author axman 2013-3-21 下午2:18:53
*/
public class ConvolutionFilter {
public enum Direction {
VERTICAL, HORIZONTAL
}
public static ImageMap convolve(ImageMap img, ConvLinearMask mask) {
ImageMap im1 = new ImageMap(img.xDim, img.yDim);
ImageMap im2 = new ImageMap(img.xDim, img.yDim);;
convolve1D(im1, mask, img, Direction.VERTICAL);
convolve1D(im2, mask, im1, Direction.HORIZONTAL);
return im2;
}
public static void convolve1D(ImageMap dest, ConvLinearMask mask, ImageMap src, Direction dir) {
int maxN; // outer loop max index
int maxP; // inner loop mac index
if (dir == Direction.VERTICAL) {
maxN = src.xDim;
maxP = src.yDim;
} else if (dir == Direction.HORIZONTAL) {
maxN = src.yDim;
maxP = src.xDim;
} else {
throw new java.lang.IllegalArgumentException("invalid direction");
}
for (int n = 0; n < maxN; n++) {
for (int p = 0; p < maxP; p++) {
double val = calculateConvolutionValue1D(src, mask, n, p, maxN, maxP, dir);
if (dir == Direction.VERTICAL) dest.valArr[p][n] = val;
else dest.valArr[n][p] = val;
}
}
}
private static double calculateConvolutionValue1D(ImageMap src, ConvLinearMask mask, int n, int p, int maxN,
int maxP, Direction dir) {
double sum = 0.0;
boolean isOut = false;
double outBound = 0.0;
for (int i = 0; i < mask.dim; i++) {
int curAbsP = i - mask.middle + p;
if (curAbsP < 0 || curAbsP >= maxP) {
isOut = true;
outBound += mask.mask[i];
continue;
}
if (dir == Direction.VERTICAL) sum += (mask.mask[i] * src.valArr[curAbsP][n]);
else sum += mask.mask[i] * src.valArr[n][curAbsP];
}
if (isOut) sum *= 1.0 / (1.0 - outBound);
return sum;
}
}