Alpha Channel Splitter

What it does

Game pipelines, compositing, and texture authoring often need the alpha channel as its own grayscale map, separate from color. This tool reads each pixel, writes the alpha value into all RGB channels of the mask image, and builds an opaque RGB-only plate (alpha forced to 255) so you can edit or recombine layers in other apps.

Why use a browser-only splitter?

NDA art, unreleased UI, and production textures should not be uploaded to random converters. This page uses the same privacy model as our WebP Image Optimizer: your file stays on your machine, and only you trigger downloads.

How it works

Your file is drawn to a canvas, then getImageData walks the bitmap. Two new bitmaps are produced and exported as PNG via toBlob. No network requests.

How to use

• Drop or select one PNG or WebP file (with or without transparency).
• Review the checkerboard preview and the status line (dimensions and alpha range).
• Download mask PNG and/or RGB plate PNG with the suggested filenames.
• Recombine or composite in your DCC or engine using the mask as alpha or layer mask.

Frequently asked questions

Does the alpha channel splitter upload my image to a server?

No. The file never leaves your device. The browser reads it with the File API, draws pixels to a canvas, and builds PNG downloads locally with toBlob.

Why is my mask solid white?

JPEG and opaque PNGs have no transparency — every pixel has alpha 255. The mask image encodes alpha in the RGB channels, so a fully opaque source produces a white mask. Use PNG or WebP that actually has transparency.

What is the difference between the mask and the RGB plate?

The mask is grayscale where each pixel’s value equals the original alpha (white = opaque, black = transparent). The RGB plate keeps the original red, green, and blue but forces alpha to 255 so you can edit color without transparency in another app.

Can I recombine the mask and RGB plate?

Yes, in Photoshop, GIMP, Krita, or game engines: use the mask as an alpha channel or as a layer mask on the RGB plate. This tool only splits; it does not merge layers back.