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 RMS Contrast Report
Measure root mean square deviation around mean decoded luminance for visible pixels and export both values as JSON.
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 RMS Contrast Report settings
This analysis uses one documented method so repeated runs on the same decoded pixels remain comparable.
Prepare the RMS luminance-contrast JSON reportThe source is not overwritten. Analysis produces a separate RMS luminance-contrast JSON report.
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 rms contrast report with an inspectable review path
Visible decoded luminance values are averaged, squared deviations from that mean are averaged, and the square root gives RMS contrast. Compare the result with the untouched source before using it downstream.Social-ready choices
Compare contrast dispersion among consistently cropped chart exports while separately checking text-to-background contrast pairs.
What you receive
Review and download a separate RMS luminance-contrast JSON report; the original file on your device remains unchanged.
Decision guide
What image rms contrast report measures or changes
Visible decoded luminance values are averaged, squared deviations from that mean are averaged, and the square root gives RMS contrast.
Global RMS dispersion ignores spatial relationships and is not WCAG text contrast, local contrast, exposure correctness, or print proofing. Browser-local processing avoids a Nirmion file upload, but it cannot remove copies stored elsewhere.
W3C relative luminance definitionUseful checks for image rms contrast report
- Compare contrast dispersion among consistently cropped chart exports while separately checking text-to-background contrast pairs.
- Create a bounded review result while retaining the original for comparison, correction, or a different method.
- Test representative flat areas, gradients, edges, text, transparency, and high-frequency texture before accepting the output.
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 RMS Contrast Report upload my image?
No. Supported JPEG, PNG, and WebP decoding, pixel inspection, transformation, and export run in your current browser tab. Nirmion does not send the selected image to its API for this workflow. The result is a separate derivative or JSON report, while the original file on your device remains unchanged and should be retained for comparison.
How does Image RMS Contrast Report work?
Visible decoded luminance values are averaged, squared deviations from that mean are averaged, and the square root gives RMS contrast. Fully transparent samples are excluded from numerical reports, while visual effects preserve source alpha. The method does not infer subjects, restore missing detail, calibrate a display, or develop raw camera data. Compare edges, gradients, text, texture, and transparent areas with the original before relying on the result.
What are the limits of Image RMS Contrast Report?
Global RMS dispersion ignores spatial relationships and is not WCAG text contrast, local contrast, exposure correctness, or print proofing. 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. Results depend on browser decoding and encoding support. Animation, raw development, ICC calibration, layer editing, and batch processing are outside this tool's verified scope.