Converting a color image to grayscale is one of the most fundamental image processing operations. The human eye perceives different colors with varying sensitivity, so a simple average of RGB channels does not produce a perceptually accurate grayscale image. Instead, a weighted sum based on human vision is used.

Given a color image represented as a 3D array (H × W × 3 with RGB channels), convert it to a grayscale image (H × W) using the luminance formula.

Algorithm

For each pixel, compute the grayscale intensity using the ITU-R BT.601 luminance weights:

These weights reflect the human eye's greater sensitivity to green light, moderate sensitivity to red, and lower sensitivity to blue.

Return an H by W list of grayscale floats.