GD imagecropauto not working with all images

[ssada1975]

Description

$im = createImage($imgfile);
$cropped = imagecropauto($im, IMG_CROP_SIDES, 0.5);

doesn't crop it

PHP Version

PHP 8.2

Operating System

Debian 11

[cmb69]

php > var_dump(imagecolorat($im,0,0));
int(921102)
php > var_dump(imagecolorat($im, imagesx($im)-1, imagesy($im)-1));
int(16777215)

The colors at the top left and the bottom right are actually different, so nothing will be cropped (not a bug, but intentional behavior; only if the colors are exactly the same, IMG_CROP_SIDES will have an effect). Note that the $threshold parameter is not used with IMG_CROP_SIDES.

The problem with this image is that there is a dark line at the left of the image; if you crop that away manually, before cropping the sides, you get an acceptable result:

$im2 = imagecrop($im, ["x"=>1, "y"=>0, "width"=>imagesx($im)-2, "height"=>imagesy($im)-1]);
$im3 = imagecropauto($im2, IMG_CROP_SIDES);

If you use IMG_CROP_THRESHOLD instead of IMG_CROP_SIDES, you may get a better result (debatable, and also depends on the $threshold value):

$im2 = imagecrop($im, ["x"=>1, "y"=>0, "width"=>imagesx($im)-2, "height"=>imagesy($im)-1]);
$im3 = imagecropauto($im2, IMG_CROP_THRESHOLD, 0.5, 0xffffff);

[ssada1975]

oh I see, thanks!