Photo Filters

Apply grayscale, sepia, invert and brightness/contrast, then export. Free, runs entirely in your browser — no signup, and nothing you paste in is uploaded.

The classics are small matrix operations. Grayscale weights the channels by perceived luminance — green counts for most, blue for least — which is why a naive average of the three produces a flat, wrong-looking result. Sepia is a similar matrix that tints while it desaturates, and invert simply subtracts each channel from its maximum.

Brightness and contrast are different in kind. Brightness adds a constant and clips at the ends, so pushing it far enough destroys detail in the highlights permanently. Contrast pivots values around the midpoint, expanding the middle of the range at the cost of both ends.