Sharpen

sharpen() increases local edge contrast with an unsharp mask.

Example

Source	Sharpened

<?php

use Alto\Image\Image;

Image::open('source-landscape.png')
    ->sharpen(sigma: 1.2, amount: 2.5)
    ->save('sharpen.png');

Options

Edge cases

• Sigma must be finite and greater than zero.
• Amount 0 leaves pixels unchanged.
• High amounts can create halos.
• Sharpen after resizing for the final output size.

Driver support

Imagick is exact. GD uses an approximate convolution.