图像处理之图像梯度效果
基本思想：
利用X方向与Y方向分别实现一阶微分，求取振幅，实现图像梯度效果。关于如何计算图像
一阶微分参见这里：http://blog.csdn.net/jia20003/article/details/7562092
使用的两种微分算子分别为Prewitt与Sobel，其中Soble在X, Y两个方向算子分别为：
Prewitt在X, Y方向上梯度算子分别为：
二：程序思路及实现
梯度滤镜提供了两个参数：
– 方向，用来要决定图像完成X方向梯度计算， Y方向梯度计算，或者是振幅计算
– 算子类型，用来决定是使用sobel算子或者是prewitt算子。
计算振幅的公式可以参见以前《图像处理之一阶微分应用》的文章
三：运行效果
原图像如下：
基于Prewitt与sobel算子的XY方向振幅效果如下：
该滤镜的源代码如下：
package com.process.blur.study; import java.awt.image.BufferedImage; /** * * @author gloomy-fish * @date 2012-06-11 * * prewitt operator * X-direction * -1, 0, 1 * -1, 0, 1 * -1, 0, 1 * * Y-direction * -1, -1, -1 * 0, 0, 0 * 1, 1, 1 * * sobel operator * X-direction * -1, 0, 1 * -2, 0, 2 * -1, 0, 1 * * Y-direction * -1, -2, -1 * 0, 0, 0 * 1, 2, 1 * */ public class GradientFilter extends AbstractBufferedImageOp { // prewitt operator public final static int[][] PREWITT_X = new int[][]{{-1, 0, 1}, {-1, 0, 1}, {-1, 0, 1}}; public final static int[][] PREWITT_Y = new int[][]{{-1, -1, -1}, {0, 0, 0}, {1, 1, 1}}; // sobel operator public final static int[][] SOBEL_X = new int[][]{{-1, 0, 1}, {-2, 0, 2}, {-1, 0, 1}}; public final static int[][] SOBEL_Y = new int[][]{{-1, -2, -1}, {0, 0, 0}, {1, 2, 1}}; // direction parameter public final static int X_DIRECTION = 0; public final static int Y_DIRECTION = 2; public final static int XY_DIRECTION = 4; private int direction; private boolean isSobel; public GradientFilter() { direction = XY_DIRECTION; isSobel = true; } public void setSoble(boolean sobel) { this.isSobel = sobel; } public int getDirection() { return direction; } public void setDirection(int direction) { this.direction = direction; } @Override public BufferedImage filter(BufferedImage src, BufferedImage dest) { int width = src.getWidth(); int height = src.getHeight(); if (dest == null ) dest = createCompatibleDestImage( src, null ); int[] inPixels = new int[width*height]; int[] outPixels = new int[width*height]; getRGB( src, 0, 0, width, height, inPixels ); int index = 0, index2 = 0; double xred = 0, xgreen = 0, xblue = 0; double yred = 0, ygreen = 0, yblue = 0; int newRow, newCol; for(int row=0; row= height) { newRow = row; } if(newCol < 0 || newCol >= width) { newCol = col; } index2 = newRow * width + newCol; tr = (inPixels[index2] >> 16) & 0xff; tg = (inPixels[index2] >> 8) & 0xff; tb = inPixels[index2] & 0xff; if(isSobel) { xred += (SOBEL_X[subrow + 1][subcol + 1] * tr); xgreen +=(SOBEL_X[subrow + 1][subcol + 1] * tg); xblue +=(SOBEL_X[subrow + 1][subcol + 1] * tb); yred += (SOBEL_Y[subrow + 1][subcol + 1] * tr); ygreen +=(SOBEL_Y[subrow + 1][subcol + 1] * tg); yblue +=(SOBEL_Y[subrow + 1][subcol + 1] * tb); } else { xred += (PREWITT_X[subrow + 1][subcol + 1] * tr); xgreen +=(PREWITT_X[subrow + 1][subcol + 1] * tg); xblue +=(PREWITT_X[subrow + 1][subcol + 1] * tb); yred += (PREWITT_Y[subrow + 1][subcol + 1] * tr); ygreen +=(PREWITT_Y[subrow + 1][subcol + 1] * tg); yblue +=(PREWITT_Y[subrow + 1][subcol + 1] * tb); } } } double mred = Math.sqrt(xred * xred + yred * yred); double mgreen = Math.sqrt(xgreen * xgreen + ygreen * ygreen); double mblue = Math.sqrt(xblue * xblue + yblue * yblue); if(XY_DIRECTION == direction) { outPixels[index] = (ta << 24) | (clamp((int)mred) << 16) | (clamp((int)mgreen) << 8) | clamp((int)mblue); } else if(X_DIRECTION == direction) { outPixels[index] = (ta << 24) | (clamp((int)yred) << 16) | (clamp((int)ygreen) << 8) | clamp((int)yblue); } else if(Y_DIRECTION == direction) { outPixels[index] = (ta << 24) | (clamp((int)xred) << 16) | (clamp((int)xgreen) << 8) | clamp((int)xblue); } else { // as default, always XY gradient outPixels[index] = (ta << 24) | (clamp((int)mred) << 16) | (clamp((int)mgreen) << 8) | clamp((int)mblue); } // cleanup for next loop newRow = newCol = 0; xred = xgreen = xblue = 0; yred = ygreen = yblue = 0; } } setRGB(dest, 0, 0, width, height, outPixels ); return dest; } public static int clamp(int value) { return value < 0 ? 0 : (value > 255 ? 255 : value); } }
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