Calculate NPCR between Images

Calculate the NPCR (Normalized Pixel Change Rate) between images

In the field of image processing, NPCR is a commonly used performance evaluation metric that measures the degree of pixel variation between two images. By counting the number of different pixels in the images, the NPCR value can be determined. When calculating NPCR, the pixel values of two images are typically compared, and the differences between them are computed. This difference can be expressed as a percentage or specific numerical value to indicate the degree of variation between the two images. Therefore, by calculating NPCR, we can quantify differences between images and evaluate the performance of image processing algorithms.

From a code implementation perspective, NPCR calculation typically involves iterating through corresponding pixels in two images and applying a threshold-based comparison. The standard formula is: NPCR = (Σ D(i,j) / (M × N)) × 100%, where D(i,j) = 0 if pixels are identical, D(i,j) = 1 if different; M and N represent image dimensions. Key implementation steps include reading images, converting to grayscale if necessary, comparing pixel values using a tolerance threshold, and summing differences. Common programming approaches utilize nested loops or vectorized operations for efficient pixel-wise comparison.