Change Image Opacity

A semi-transparent image is useful as a watermark, a faded background behind text, a ghosted overlay in a design, or a lighter version of a logo. This tool lowers the opacity of every pixel by the percentage you choose, or fades it gradually towards one edge or the corners. Existing transparency is respected, and the result is a PNG or WebP that keeps its alpha channel. Images are processed in your browser and never uploaded.

How to use this tool

1. Choose one or more images (JPG, PNG, WebP, HEIC and more).
2. Set the opacity: 100% leaves the image unchanged, 0% makes it invisible.
3. Apply it evenly, or as a fade towards an edge or the corners.
4. Download the PNG (lossless) or WebP (smaller) file.

Formula

new alpha = old alpha × (1 − (1 − opacity) × t)

t is 1 everywhere for an even change. For a fade it runs from 0 at the starting edge to 1 at the far edge (x ÷ (width − 1) for a fade to the right), or from the centre to the corners for the vignette. Colour values are not changed, only the alpha channel, so a picture placed over white looks lighter and over black looks darker.

Example

At 50% an opaque pixel's alpha becomes 255 × 0.5 = 127.5, stored as 128. A pixel that was already 40% transparent (alpha 153) becomes 153 × 0.5 = 77. With a fade to the right at 0%, the left column stays fully visible and the right column becomes invisible; the middle of a 1001-pixel-wide image gets alpha 255 × 0.5 = 128.