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Image Tools / Local studio

Image Alpha Coverage Report

Count fully transparent, partially transparent, and fully opaque decoded pixels and export their exact canvas coverage as JSON.

Runs locallyNo image upload to Nirmion

Step 1 / Source

Choose one image

JPEG · PNG · WebP · 20 MB

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 megapixels

Step 2 / Output

Image Alpha Coverage Report settings

This analysis uses one documented method so repeated runs on the same decoded pixels remain comparable.

Prepare the alpha-coverage JSON reportThe source is not overwritten. Analysis produces a separate alpha-coverage 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 alpha coverage report with an inspectable review path

Every decoded alpha byte is classified as zero, one through 254, or 255; counts and total-canvas percentages are reported. Compare the result with the untouched source before using it downstream.
A

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.

B

Social-ready choices

Check whether an authorised PNG asset contains unexpected partial edges or a fully opaque background before downstream delivery.

C

What you receive

Review and download a separate alpha-coverage JSON report; the original file on your device remains unchanged.

Decision guide

What image alpha coverage report measures or changes

Every decoded alpha byte is classified as zero, one through 254, or 255; counts and total-canvas percentages are reported.

Alpha occupancy does not reveal visual correctness, compositing appearance, matte contamination, hidden RGB, or support in a destination format. Browser-local processing avoids a Nirmion file upload, but it cannot remove copies stored elsewhere.

MDN Canvas pixel manipulation

Useful checks for image alpha coverage report

  1. Check whether an authorised PNG asset contains unexpected partial edges or a fully opaque background before downstream delivery.
  2. Create a bounded review result while retaining the original for comparison, correction, or a different method.
  3. 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 Alpha Coverage 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 Alpha Coverage Report work?

Every decoded alpha byte is classified as zero, one through 254, or 255; counts and total-canvas percentages are reported. 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 Alpha Coverage Report?

Alpha occupancy does not reveal visual correctness, compositing appearance, matte contamination, hidden RGB, or support in a destination format. 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.