Apologies I reversed the ifdef in my head, I should have pasted the else branch, it too sets the same variable, which appears to be part of the context of dcraw rather than the LibRaw code which is testing in convert_to_rgb_loop the value in the libraw_internal_data.internal_output_params.raw_color. I had imagined the intent was to avoid the matrix multiply when the matrix is unity.

Re subclassing - fine with me I'm probably going to combine that and some other code into a single pass over the memory as easy wins in performance.

Thanks for your efforts in producing the library much easier to use than the dcraw code direct.

Kevin