Open Radar

 
I've run into a problem with a custom filter (homography) that renders blurry image at top right image corner when rendered with CPU context. That same filter renders correctly with a GPU context.

I isolated the problem in the provided sample code (and I also included output images, CPU and GPU). In that example, the homography is just the identity matrix to demonstrate the issue (output image should be the same as input image). What I observe is that on a CPU context, the image get blurry in the top right corner. That same code running on a GPU context is perfectly sharp. 

I further investigated that problem, it seems to come from the division. If I replace this line: 

src = tmp.xy / tmp.z;

by this:

src = tmp.xy;

Both rendered images are perfectly sharp. (tmp.z is equal to 1.0 in the first case).

This is a problem in our application, because we specifically use the software context because we assume it produces higher quality images. This is not the case, because of this precision problem.