java 突出图像之间的差异
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Highlight differences between images
提问by user3078335
There is this image comparison code I am supposed to modify to highlight/point out the difference between two images. Is there a way to modify this code so as to highlight the differences in images. If not any suggestion on how to go about it would be greatly appreciated.
我应该修改此图像比较代码以突出显示/指出两个图像之间的差异。有没有办法修改此代码以突出图像中的差异。如果没有关于如何进行的任何建议，将不胜感激。
int width1 = img1.getWidth(null);
int width2 = img2.getWidth(null);
int height1 = img1.getHeight(null);
int height2 = img2.getHeight(null);
if ((width1 != width2) || (height1 != height2)) {
System.err.println("Error: Images dimensions mismatch");
System.exit(1);
}
long diff = 0;
for (int i = 0; i < height1; i++) {
for (int j = 0; j < width1; j++) {
int rgb1 = img1.getRGB(j, i);
int rgb2 = img2.getRGB(j, i);
int r1 = (rgb1 >> 16) & 0xff;
int g1 = (rgb1 >> 8) & 0xff;
int b1 = (rgb1) & 0xff;
int r2 = (rgb2 >> 16) & 0xff;
int g2 = (rgb2 >> 8) & 0xff;
int b2 = (rgb2) & 0xff;
diff += Math.abs(r1 - r2);
diff += Math.abs(g1 - g2);
diff += Math.abs(b1 - b2);
}
}
double n = width1 * height1 * 3;
double p = diff / n / 255.0;
return (p * 100.0);
回答by Nick Grealy
This solution did the trick for me. It highlights differences, and has the best performance out of the methods I've tried. (Assumptions: images are the same size. This method hasn't been tested with transparencies.)
这个解决方案对我有用。它突出了差异，并且在我尝试过的方法中具有最佳性能。（假设：图像大小相同。此方法尚未使用透明胶片进行测试。）
Average time to compare a 1600x860 PNG image 50 times (on same machine):
比较 1600x860 PNG 图像 50 次的平均时间（在同一台机器上）：
- JDK7 ~178 milliseconds
- JDK8 ~139 milliseconds
- JDK7 ~178 毫秒
- JDK8 ~139 毫秒
Does anyone have a better/faster solution?
有没有人有更好/更快的解决方案？
public static BufferedImage getDifferenceImage(BufferedImage img1, BufferedImage img2) {
// convert images to pixel arrays...
final int w = img1.getWidth(),
h = img1.getHeight(),
highlight = Color.MAGENTA.getRGB();
final int[] p1 = img1.getRGB(0, 0, w, h, null, 0, w);
final int[] p2 = img2.getRGB(0, 0, w, h, null, 0, w);
// compare img1 to img2, pixel by pixel. If different, highlight img1's pixel...
for (int i = 0; i < p1.length; i++) {
if (p1[i] != p2[i]) {
p1[i] = highlight;
}
}
// save img1's pixels to a new BufferedImage, and return it...
// (May require TYPE_INT_ARGB)
final BufferedImage out = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
out.setRGB(0, 0, w, h, p1, 0, w);
return out;
}
Usage:
用法：
import javax.imageio.ImageIO;
import java.io.File;
ImageIO.write(
getDifferenceImage(
ImageIO.read(new File("a.png")),
ImageIO.read(new File("b.png"))),
"png",
new File("output.png"));
回答by rayryeng
What I would do is set each pixel to be the difference between one pixel in one image and the corresponding pixel in the other image. The difference that is being calculated in your original code is based on the L1norm. This is also called the sum of absolute differencestoo. In any case, write a method that would take in your two images, and return an image of the same size that sets each location to be the difference for each pair of pixels that share the same location in the final image. Basically, this will give you an indication as to which pixels are different. The whiter the pixel, the more difference there is between these two corresponding locations.
我要做的是将每个像素设置为一张图像中的一个像素与另一张图像中的相应像素之间的差值。在您的原始代码中计算的差异基于L 1norm。这也称为绝对差的总和。在任何情况下，编写一个方法来接收您的两个图像，并返回一个相同大小的图像，该图像将每个位置设置为最终图像中共享相同位置的每对像素的差异。基本上，这将为您提供有关哪些像素不同的指示。像素越白，这两个对应位置之间的差异越大。
I'm also going to assume you're using a BufferedImageclass, as getRGB()methods are used and you are bit-shifting to access individual channels. In other words, make a method that looks like this:
我还将假设您正在使用一个BufferedImage类，因为使用了getRGB()方法并且您正在位移以访问单个频道。换句话说，创建一个如下所示的方法：
public static BufferedImage getDifferenceImage(BufferedImage img1, BufferedImage img2) {
int width1 = img1.getWidth(); // Change - getWidth() and getHeight() for BufferedImage
int width2 = img2.getWidth(); // take no arguments
int height1 = img1.getHeight();
int height2 = img2.getHeight();
if ((width1 != width2) || (height1 != height2)) {
System.err.println("Error: Images dimensions mismatch");
System.exit(1);
}
// NEW - Create output Buffered image of type RGB
BufferedImage outImg = new BufferedImage(width1, height1, BufferedImage.TYPE_INT_RGB);
// Modified - Changed to int as pixels are ints
int diff;
int result; // Stores output pixel
for (int i = 0; i < height1; i++) {
for (int j = 0; j < width1; j++) {
int rgb1 = img1.getRGB(j, i);
int rgb2 = img2.getRGB(j, i);
int r1 = (rgb1 >> 16) & 0xff;
int g1 = (rgb1 >> 8) & 0xff;
int b1 = (rgb1) & 0xff;
int r2 = (rgb2 >> 16) & 0xff;
int g2 = (rgb2 >> 8) & 0xff;
int b2 = (rgb2) & 0xff;
diff = Math.abs(r1 - r2); // Change
diff += Math.abs(g1 - g2);
diff += Math.abs(b1 - b2);
diff /= 3; // Change - Ensure result is between 0 - 255
// Make the difference image gray scale
// The RGB components are all the same
result = (diff << 16) | (diff << 8) | diff;
outImg.setRGB(j, i, result); // Set result
}
}
// Now return
return outImg;
}
To call this method, simply do:
要调用此方法，只需执行以下操作：
outImg = getDifferenceImage(img1, img2);
This is assuming that you are calling this within a method of your class. Have fun and good luck!
这是假设您在类的方法中调用它。玩得开心，祝你好运！
