Blurring RGB images? #24
Description
Right now the functions blur and gaussianBlur in Vision.Image.Filter impose the constraint Integral (ImagePixel src) on the source image. However, this seems like an unnecessary constraint, which prevents one from, for example, blurring RGB or RGBA images. As I understand it, only addition and multiplication (by a scalar) operations are required for the pixels in order to do the convolution. One could sensibly define these operations for RGB and RGBA pixels. Maybe one could find or define a weaker typeclass to use as a constraint. Another option would be to have an intermediate function which would allow applying a filter component-wise.