Fix resize when image is smaller than the target size

[lucasvazq]

Description

If the png icon is 400x400px, when it's been resized to accomplish for the manifest sizes, the result of the bigger of them (512x512px) keeps bad resized. The source image set in the center of the new image with 400x400 px and now have 56px padding border

[subzero-taringuero]

Thanks for opening this issue!