Default image filter doesn't affect canvases

Issue #525 resolved
hahawoo
created an issue

The default image filter set by love.graphics.setDefaultImageFilter doesn't affect canvases. Maybe this is because it's the default image filter, but seeing as though it works with ImageFonts too since 0.8.1 perhaps it could work with canvases as well. And if this sounds like a good idea, maybe it should be renamed to something like setDefaultFilter.