Metal Core Image kernel workingColorSpace

Question

I understand that by default, Core image uses extended linear sRGB as default working color space for executing kernels. This means that the color values received (or sampled from sampler) in the Metal Core Image kernel are linear values without gamma correction applied. But if we disable color management by setting

let options:[CIContextOption:Any] = [CIContextOption.workingColorSpace:NSNull()];

do we receive color values as it exists in the input texture (which may have gamma correction already applied)? In other words, the color values received in the kernel are gamma corrected and we need to manually convert them to linear values in the Metal kernel if required?

Answer 1

Yes, this should be the case: you receive the color values as they are defined in the input image without any conversion when you disable color management.

Apple seems to have designed this API specifically for working with raw input data that doesn't necessarily encode color values:

To request that Core Image perform no color management, specify the NSNull object as the value for this key. Use this option for images that don’t contain color data (such as elevation maps, normal vector maps, and sampled function tables).

– Documenation of CIContextOption.workingColorSpace