What you need
Choose one authorised JPEG, PNG, or WebP still image up to 20 MB and 12 million decoded pixels. Animated frames are not processed.
Image Tools / Local studio
Image Auto Contrast Stretch
Stretch each visible RGB channel from its observed minimum to maximum, preserve alpha and dimensions, and export locally.
Runs locallyNo image upload to Nirmion
Step 1 / Source
Choose one image
Drop your image here
Or browse for a JPEG, PNG, or WebP image that you own or are authorised to edit.
One file · up to 20 MB · maximum 50 megapixelsStep 2 / Output
Image Auto Contrast Stretch controls
No manual strength is required; visible decoded pixels determine each channel range and flat channels remain unchanged. Processing stays in this browser tab.
Create the auto-contrast imageThe source is not overwritten. Export creates a separate auto-contrast image.
Keep this page open until the download begins.01No server upload
The selected image is decoded and re-encoded inside this browser tab.
02Working copy released
After download, the preview URL, decoded bitmap, canvas, and selected source reference are cleared.
03Your download remains
Nirmion cannot remove the finished file from your device or browser download history.
Workflow guide
Use image auto contrast stretch with a reversible review path
The tool finds visible-pixel minimum and maximum values per RGB channel, maps each non-flat range to 0-255, and leaves flat channels unchanged. Compare the derivative with the untouched source before using it downstream.Social-ready choices
Expand a faded scan review copy while checking whether independent channel stretching introduces an unwanted colour cast.
What you receive
Download a separate auto-contrast image; the original file on your device remains unchanged.
Decision guide
What image auto contrast stretch changes
The tool finds visible-pixel minimum and maximum values per RGB channel, maps each non-flat range to 0-255, and leaves flat channels unchanged.
Per-channel endpoint stretching can clip outliers and shift colour balance; it is not histogram equalization, local contrast, or calibrated restoration. Browser-local processing avoids a Nirmion file upload, but it cannot remove copies stored elsewhere.
MDN Canvas pixel manipulationUseful checks for image auto contrast stretch
- Expand a faded scan review copy while checking whether independent channel stretching introduces an unwanted colour cast.
- Create a review derivative while retaining the original for correction, comparison, or a different export.
- Test the operation on representative shadows, midtones, highlights, edges, text, and transparent areas.
Good to know
Important image boundaries
- Why might a PNG not become smaller?
- PNG is lossless and browsers do not expose a quality control for it. Choose WebP or JPEG when reducing file size matters more than exact lossless pixels.
- Are animated images supported?
- No. The workspace accepts still JPEG, PNG, and WebP files. Re-encoding an animated source would otherwise keep only one frame.
- What does clearing the file mean?
- Because processing is local, there is no Nirmion server copy to delete. The tab releases its working references after success; your downloaded output remains on your device.
Questions answered
Frequently asked questions
Does Image Auto Contrast Stretch upload my image?
No. For supported JPEG, PNG, and WebP inputs, decoding, pixel transformation, canvas rendering, and export run in your current browser tab. Nirmion does not send the selected image to its API for this workflow. The output is a new derivative, while the original file on your device remains unchanged and should be retained for comparison or later editing.
How does Image Auto Contrast Stretch change pixels?
The tool finds visible-pixel minimum and maximum values per RGB channel, maps each non-flat range to 0-255, and leaves flat channels unchanged. Existing alpha values are preserved. The operation does not infer subjects, recover clipped detail, calibrate a display, or develop raw camera data. Inspect fine edges, gradients, text, skin tones, and transparent pixels in the exported file before relying on the result.
What are the practical limits of Image Auto Contrast Stretch?
Per-channel endpoint stretching can clip outliers and shift colour balance; it is not histogram equalization, local contrast, or calibrated restoration. The workspace accepts one supported still image up to 20 MB and caps this pixel-intensive operation at 12 million decoded pixels for predictable browser memory use. Output depends on browser decoding and encoding support. Animation, raw development, ICC calibration, layer editing, and batch processing are outside this tool's verified scope.