I'm trying to transform a rectangle to an quadrilateral and created a CATransform3D projection matrix as described by hfossli here.
The matrix works with a CALayer with out problem, but i would like/have to use it with GPUImage and the GPUImageTransformFilter, which takes a CATransform3D.
It doesn't really work.
The scaling doesn't fit, which means my transformed image gets cut of or points are not "stretched" to the position they should be. There are some threads which describe the translation from a OpenGL projection to a proper CATransform3D projection matrix like here.
It involves some scaling and y-flipping.
So I tried to scale and flip in reversed order in the hope to be able to use this CATransform3D matrix with the GPUImageTransformFilter, but couldn't really get it to work.
Did maybe someone solve this?
