Flatten

flatten() composites transparent pixels onto a background.

Example

Transparent source	Cyan background

<?php

use Alto\Image\Image;

Image::open('source-transparent.png')
    ->flatten('#00b7ff')
    ->save('flatten.png');

Options

Edge cases

• An opaque source is unchanged.
• An opaque background removes alpha.
• A transparent background can preserve alpha.
• Flatten before JPEG encoding to control the replacement colour.

Driver support

GD and Imagick support flatten() exactly.