qcam: viewfinder_gl: Add support for RGB formats

Add support for 24-bit and 32-bit RGB formats. The fragment samples the
texture and reorders the components, using a pattern set through the
RGB_PATTERN macro. The pattern stores the shader vec4 element indices
(named {r, g, b, a} by convention, for elements 0 to 3) to be extracted
from the texture samples, when interpreted by OpenGL as RGBA.

Note that, as textures are created with GL_UNSIGNED_BYTE, the RGBA
order corresponds to bytes in memory, while the libcamera formats are
named based on the components order in a 32-bit word stored in memory in
little endian format.

An alternative to manual reordering in the shader would be to set the
texture swizzling mask. This is however not available in OpenGL ES
before version 3.0, which we don't mandate at the moment.

Only the BGR888 and RGB888 formats have been tested, with the vimc
pipeline handler.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Andrey Konovalov <andrey.konovalov@linaro.org>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

0 files changed, 0 insertions, 0 deletions