The structure should not be changed, despite the union modification.
I am renaming for consistency with older branches that had a mask
field in RGBA_Image. Also, the mask.data or data8 is really just
a way to avoid casting between DATA8 and DATA32 (and it shows
clearly what kind of data you are dealing with).
If the displacement map has some alpha values (not 0xFF),
then the blending should take this alpha into account. This
part is fine.
BUT, since Evas relies on premultiplied colors... we have a
problem: R (dx) and G (dy) have already been scaled down.
Actually we would need to load the map in non premultiplied RGBA,
otherwise we'll lose precision on dx,dy as soon as A != 0xFF.
Well... I guess this will be a limitation of this filter, for now
at least. Most displacement maps shouldn't even have any alpha
anyways.
The displacement effect is way too complicated. Let's keep it
simple and have only one displacement map format (RG + Alpha).
Here's what's missing now:
- Alpha support, to blend in the input with a variable intensity
- Extra padding (see below)
Also, the intensity VS. map values are not perfectly defined yet.
Problems: How to create a complete mirror effect (map needs to go
over boundaries... add extra padding to the buffers).
Displacement maps are a simple but powerful tool to move pixels
around in a buffer, based on a displacement map (image).
Currently, various modes are implemented:
- X, Y or XY displacement
- Alpha map or RGBA map where R and G only are used
An intensity parameter is given as well.
Some of these might not be useful, we can just strip them off when
the final API is decided.
Jean-Philippe Andre