Rounding issue when using focal point cropping results in 1px white line

[thopra]

When using focal point cropping (e.g. test.jpg?w=600&h=250&fit=crop-33-66), depending on the aspect ratio and dimensions of the original image, in some cases the cropped result contains a one pixel white line on either edge.

Cause

This happens, because before the image is cropped, it is scaled down to the given dimensions while keeping aspect ratio. Width and height are rounded (see Manipulators/Size.php) - which as a result, can be less than the width or height that are passed to cropping, causing the crop offset to be wrong and a pixel of the white background color to not be covered by the image.

$image->scale((int) round($resize_width * $zoom), (int) round($resize_height * $zoom));

[$offset_x, $offset_y] = $this->resolveCropOffset($image, $width, $height);
// ^-- $width (or $height) can differ by 1 to width and height of the scaled image, 
// which could be rounded down, resulting in $offset_x being -1

return $image->crop($width, $height, $offset_x, $offset_y, 'transparent');

Example

Here's an example of a 1920x1278 source image:

And here's the result, cropped with the following parameters:

test.jpg?w=600&h=250&fit=crop-0-50

Suggested fix

Simply changing the rounding function for parameters passed to the scaling method mentioned above to ceil() instead of round() fixes the issue, because then the scaled image will have at least the size of the given crop dimensions.

$image->scale((int) ceil($resize_width * $zoom), (int) ceil($resize_height * $zoom));