IMAGE PROCESSING REFERENCE
Calculate how an RGB pixel changes when a saturation adjustment is applied. This page documents the formula used by FileTools' browser image processor.
Grayscale value: 150.66
Saturation multiplier: 1.50×
Adjusted RGB: (105, 195, 45)
For each pixel, the processor calculates grayscale intensity as 0.299R + 0.587G + 0.114B. It then applies the saturation factor to each colour channel.
factor = 1 + amount output = clamp(gray + (channel - gray) × factor, 0, 255)The clamp keeps every output channel inside the 8-bit RGB range. An amount of 0 therefore has a factor of 1 and leaves the channel unchanged.
| Amount | Multiplier |
|---|---|
| -1.00 | 0.00× |
| -0.75 | 0.25× |
| -0.50 | 0.50× |
| -0.25 | 0.75× |
| 0.00 | 1.00× |
| 0.25 | 1.25× |
| 0.50 | 1.50× |
| 1.00 | 2.00× |
| 2.00 | 3.00× |
| 3.00 | 4.00× |
Negative values move RGB channels toward grayscale. Positive values increase their distance from grayscale. Strong positive values can cause channel clipping.
This page describes FileTools' RGB-channel adjustment, not an HSL or HSV conversion. Different image editors can therefore produce different results for the same saturation percentage.
When you are ready to edit a real image, use the free image saturation editor. The processing runs locally in your browser.