DemosaicedImage gains a second producer, from_rgba8, alongside the CFA path.
Nothing about the type is CFA-specific — it is "an image on the GPU, ready to
adjust" — which is what lets develop mode work on a JPEG without the edit
graph or any operation knowing the source was not a RAW file.
The one real difference is the transfer function: sensor data is linear, a
JPEG is gamma-encoded. Every operation assumes linear scene-referred colour
(exposure is a multiply, and doubling a gamma-encoded value is not a stop), so
the shader prologue linearises once, at the only point where the two source
kinds still differ. The flag rides in as_shot_wb.w, which was padding. For a
JPEG the white balance uniform is neutral and the colour matrix is identity,
so both stay unconditional multiplies rather than becoming branches.
max_dimension is exposed because it is a hardware limit the caller must plan
around, not a failure to report afterwards: a 13728x8928 film scan exceeds the
common 8192 texture limit, and fitting it first is the only way to develop it
at all.
Assisted-by: LLM
dtourolle
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