计算图像的峰值信噪比(PSNR)——科普文章
引言
在数字图像处理中,峰值信噪比(Peak Signal-to-Noise Ratio,PSNR)是一种用于评估图像质量的指标。PSNR通常用于比较原始图像和压缩后的图像之间的差异,或者用于评估图像恢复算法的效果。在本文中,我们将了解PSNR的基本概念,并使用Java编写一个可以计算PSNR的示例代码。
PSNR的定义
峰值信噪比是通过计算信号的峰值功率和均方根误差之间的比值来衡量图像质量的指标。PSNR的公式如下:
 {
String originalImagePath = "original.png";
String comparedImagePath = "compared.png";
try {
BufferedImage originalImage = ImageIO.read(new File(originalImagePath));
BufferedImage comparedImage = ImageIO.read(new File(comparedImagePath));
double mse = calculateMeanSquareError(originalImage, comparedImage);
double psnr = calculatePSNR(mse);
System.out.println("PSNR: " + psnr + " dB");
} catch (IOException e) {
e.printStackTrace();
}
}
private static double calculateMeanSquareError(BufferedImage originalImage, BufferedImage comparedImage) {
int width = originalImage.getWidth();
int height = originalImage.getHeight();
long squareError = 0;
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++) {
int originalPixel = originalImage.getRGB(x, y);
int comparedPixel = comparedImage.getRGB(x, y);
int originalRed = (originalPixel >> 16) & 0xff;
int originalGreen = (originalPixel >> 8) & 0xff;
int originalBlue = originalPixel & 0xff;
int comparedRed = (comparedPixel >> 16) & 0xff;
int comparedGreen = (comparedPixel >> 8) & 0xff;
int comparedBlue = comparedPixel & 0xff;
int redDiff = originalRed - comparedRed;
int greenDiff = originalGreen - comparedGreen;
int blueDiff = originalBlue - comparedBlue;
squareError += redDiff * redDiff + greenDiff * greenDiff + blueDiff * blueDiff;
}
}
return (double) squareError / (width * height * 3);
}
private static double calculatePSNR(double meanSquareError) {
double maxPixelValue = 255;
return 10 * Math.log10(maxPixelValue * maxPixelValue / meanSquareError);
}
}
上述代码首先通过ImageIO
类读取原始图像和待比较图像,然后使用calculateMeanSquareError
方法计算均方误差,最后通过calculatePSNR
方法计算PSNR值,并输出结果。
序列图
下面是计算PSNR的示例代码的序列图:
sequenceDiagram
participant User
participant PSNRCalculator
participant ImageIO
participant BufferedImage
participant File
User->>PSNRCalculator: 执行计算PSNR
PSNRCalculator->>ImageIO: 读取原始图像