This makes weston_color_transform object be able to express
three-channel one-dimensional look-up table transformations. They are
useful for applying EOTF and EOTF^-1 mapping, or, gamma curves. They
will also be useful in optimizing a following 3D LUT tap distribution
once support for 3D LUT is added.
The code added here translates from the lut_3x1d fill_in() interface to
a GL texture to be used with SHADER_COLOR_CURVE_LUT_3x1D for
weston_surfaces.
It demonstrates how renderer data is attached to weston_color_transform
and cached.
GL_OES_texture_float_linear is required to be able to use bilinear
texture filtering with 32-bit floating-point textures, used for the LUT.
As the size of the LUT depends on what implements it, lut_3x1d fill_in()
interface is a callback to the color management component to ask for an
arbitrary size. For GL-renderer this is not important as it can easily
realize any LUT size, but when DRM-backend wants to offload the EOTF^-1
mapping to KMS (GAMMA_LUT), the LUT size comes from KMS.
Nothing actually implements lut_3x1d fill_in() yet, that will come in a
later patch.
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Pekka Paalanen