Dislocated file thumbnail image on MacOS

[Iraka-C]

When there includes some transparent pixels (such as draw something on the first layer and turn off the background layer), the thumb generated in the file selector seems not the whole canvas viewport, but the left-top corner collides with the contents in the first layer.

Only on MacOS (Safari & Firefox). On Windows10, Chrome & Firefox works fine.

[Iraka-C]

This can also be seen after enlarging an image with a negative left/top margin.