Online Image Grayscale Tool
Convert color images to grayscale completely. Processing takes place locally in your browser.
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What this tool actually does
Computes lum=0.299*r+0.587*g+0.114*b and assigns lum to all three RGB channels. No additional operation parameter is exposed.
Checkable behavior
Worked example: a pure red source pixel RGB(255,0,0) gives lum=76.245 and approximately RGB(76,76,76) in the byte-backed image. Pure green maps to approximately 150, pure blue approximately 29.
Controls, output and limitations
This is weighted grayscale, not binary thresholding and not a plain arithmetic channel average. The result retains gray levels rather than only black and white.
Once exported as gray, the original color cannot be inferred uniquely. Keep the original if color is needed later.
Single-image browser-local processing, preview and downloadable result. This page has no grayscale-strength or batch controls; exported color profiles may differ from the original.
The weights operate directly on the browser-decoded RGB bytes, without gamma linearization. This is an approximation of luma, not physical luminance or the relative luminance used in accessibility contrast calculations; equal perceived brightness is not guaranteed. The decoded alpha byte is copied unchanged. Output dimensions are unchanged, and the PNG filename adds -grayscale.png to the source base name.
One source image is processed at a time, up to 25 MiB (26214400 bytes) and 24000000 pixels. PNG export saves the browser-decoded canvas, not the original encoded file: animation, EXIF and color-profile metadata may be lost or changed. Width and height remain unchanged, but file identity and exact source color representation are not guaranteed. Retain the original.
Processing takes place locally in your browser.