What this slider actually does
- Linear darken
- Same percentage subtracted from each color channel per step on the slider. Hue stays stable because the mix ratios between channels do not change.
- Strength
- At zero you see the decoded file. At one hundred you see black wherever alpha is opaque. Values between scale RGB toward zero together.
Each pixel keeps its red, green, blue triple. We multiply all three by 1 - strength, where strength is zero at the left and one at the right. Alpha stays put, which matters for PNGs with transparency.
| Setting | Effect |
|---|
| 0% | Identity. Output matches the upload. |
| 25% | Mild pull. Good for slight glare on paper. |
| 50% | Half luminance on every channel. Noticeable mood shift. |
| 100% | Black frame except where alpha is zero. Useful as a sanity check, rarely as a final look. |
Gamma-based curves bend midtones without crushing highlights the same way. This tool does not do curves. For a wider tonal tool, open brightness and contrast or gamma correction on Toolexe after you know how far linear darken should go.
Three places linear darken helps
Product shots on white seamless: specular patches clip to pure white. A twenty percent linear pass often brings edge detail back without touching saturation.
Slides exported from presentation software: backgrounds arrive hotter than intended. Darkening the whole raster is faster than re-exporting master slides when you only need a PDF thumbnail.
Scanned receipts with faded thermal ink: aggressive darken is risky, yet a small reduction in paper brightness sometimes lifts letterforms relative to the background before OCR.
From file bytes to the second canvas
The browser decodes your file into a bitmap. We copy those numbers into an off-screen canvas the same width and height as your image, read the raster once, then write a fresh buffer for the preview on every slider move.
No server round trip means no queue, no account, no watermark. It also means a ten thousand pixel edge square will stutter on an older phone. There is no magic resize here; visit resizer first if you need a smaller working copy.
Judgment call: if highlights are fine shadows are empty, linear darken will only make the shadows worse. Reach for
contrast enhancement or lift shadows in software that supports local adjustments.
What this page refuses to do
Batch folders, RAW development, CMYK soft proofing, and printer ICC previews are all out of scope. Export is PNG to keep alpha predictable. JPEG recompression is intentionally not bundled because a second lossy pass hides artifacts until you zoom in.
Color cast from mixed lighting will not vanish because all channels move together. For deliberate warmth or cool shifts, pair this step with color balance or sepia when the story calls for it.
We also skip face-aware exposure, sky selection, and depth maps. Those models need heavier bundles than a single canvas tutorial should load. If you need one-click HDR recovery, use desktop RAW software, then return here for a final mild darken before social crops.
