Replace colour

Replace colour swaps one colour in an image for another: click the colour you want gone, choose what takes its place, and set how close a match has to be to count. Up to eight replacements run together in a single pass, each measured against the pixel as it arrived rather than against what an earlier pair wrote, so red-to-blue followed by blue-to-green cannot quietly turn the reds green. Preserve lightness keeps every pixel's own brightness and takes only the hue and saturation of the new colour, so the shading that told you the logo was a sphere survives.

How it works

  1. Drop in one image This tool works on one image at a time. Drop several and the first is kept, with a note saying so.
  2. Click the colour you want to replace Move the pointer over the image to read the colour under it, then click to pick that colour into the selected replacement. You can also type a hex value into the swatch.
  3. Set the replacement, tolerance and softness Tolerance is how far a pixel may sit from the picked colour and still count, from 0 — that exact colour only — to 100. Softness fades the change out across the edge of the match instead of stopping dead at it, which anti-aliased edges need.
  4. Add more replacements if you need them Up to eight pairs at once. Where two pairs match the same pixel the closer match wins, and the tool names the pairs that overlap.
  5. Export the recoloured image Choose a format, then press Export. The replacement is rerun over the full-resolution pixels before the file is written, whatever size the preview was drawn at.

Questions

How does it decide whether a pixel matches?
By straight RGB distance from the colour you picked, with tolerance read as a percentage of the longest diagonal of the RGB cube. That means two colours reading as the same hue but differing in brightness will not always match together, so a shaded or gradient-filled logo usually needs a higher tolerance, several pairs, or preserve lightness turned on.
Can I replace a colour across a batch of images?
No. Replace colour takes one image at a time — drop a batch and only the first is kept. Picking a colour, judging the tolerance and reading the match percentage all depend on you looking at that one image.
Is the matched percentage exact?
No. It is measured on the preview, which is drawn at up to 1400 pixels on its long edge, so it is close rather than exact. It is there to tell you whether the tolerance is roughly right; the export itself always runs over the image's full-resolution pixels.

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