Peak Signal-to-Noise Ratio (PSNR)

The Peak Signal-to-Noise Ratio (PSNR) is a non-linear full-reference metric that compares the pixel values of the original reference image to the values of the degraded image. PSNR is a long established image quality metric, most commonly used to compare the compression of different codecs, such as image compression.

Example: An engineer is creating a new image compression technique. To prove its effectiveness, they'd use PSNR as an objective yardstick. They'd take a pristine, uncompressed picture and process it with their new method and a competitor's. After calculating the PSNR for both resulting images, they can directly compare the scores. For example, if their new method achieves a score of 35 dB while the old one only reaches 30 dB, they have clear evidence that their algorithm provides superior image quality for the same file size.