Black and White Image Converter - Grayscale Image Online

What the Black & White Converter Does

This tool decodes your image onto an in-browser canvas and rewrites every pixel, replacing its red, green, and blue values with a single gray value. The interesting part is how that one value gets calculated, because there is no single correct answer and the four options here produce visibly different pictures from the same source. Luminance uses the BT.601 weighting, 0.299 red plus 0.587 green plus 0.114 blue. Green carries more than half the weight because the human eye is far more sensitive to green light than to red or blue, so this formula tracks how bright each color actually looks. BT.709 does the same job with weights tuned for the primaries of modern HDTV and sRGB displays, 0.2126 red, 0.7152 green, 0.0722 blue — greens get lighter still and reds go noticeably darker. Average simply divides the sum of the three channels by three; it ignores perception entirely, so saturated reds and deep blues come out brighter than they appear to the eye, and skies often look washed out. Lightness takes the midpoint between the brightest and darkest channel, which discards hue information altogether and tends to flatten the image into a narrower band of mid-grays. After the gray value is chosen, brightness shifts it by a flat offset and contrast applies the standard factor curve around mid-gray. The sepia option multiplies the finished gray by fixed per-channel coefficients to produce a warm brown tint. Alpha is copied through untouched, so a transparent PNG stays transparent.