Below is the code for converting a image to Negative

<?php
$img = imagecreatefrompng(‘images.png’);
imagefilter($img,IMG_FILTER_NEGATE);
imagepng($img,’negative.png’);
imagedestroy($img);
?>

Here images.png is original image and negative.png is the converted negative image.

In the first line of code use imagecreatefromgif() if you are converting a gif image ,use imagecreatefromjpeg()  if you are converting a jpeg image, user imagecreatefrombmp() if you are converting a bmp image

Similarly in line 3 use imagegif() for creating negative in gif format, use imagejpeg() for jpeg format,imagebmp for bmp format.

Say thanks in comment if it helps you 🙂