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noodleBowl

DX11 Question about WIC Pixel format conversions

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I was wondering if someone could explain this to me

I'm working on using the windows WIC apis to load in textures for DirectX 11. I see that sometimes the WIC Pixel Formats do not directly match a DXGI Format that is used in DirectX. I see that in cases like this the original WIC Pixel Format is converted into a WIC Pixel Format that does directly match a DXGI Format. And doing this conversion is easy, but I do not understand the reason behind 2 of the WIC Pixel Formats that are converted based on Microsoft's guide

I was wondering if someone could tell me why Microsoft's guide on this topic says that GUID_WICPixelFormat40bppCMYKAlpha should be converted into GUID_WICPixelFormat64bppRGBA and why GUID_WICPixelFormat80bppCMYKAlpha should be converted into GUID_WICPixelFormat64bppRGBA

In one case I would think that: 
GUID_WICPixelFormat40bppCMYKAlpha would convert to GUID_WICPixelFormat32bppRGBA and that GUID_WICPixelFormat80bppCMYKAlpha would convert to GUID_WICPixelFormat64bppRGBA, because the black channel (k) values would get readded / "swallowed" into into the CMY channels

In the second case I would think that:
GUID_WICPixelFormat40bppCMYKAlpha would convert to GUID_WICPixelFormat64bppRGBA and that GUID_WICPixelFormat80bppCMYKAlpha would convert to GUID_WICPixelFormat128bppRGBA, because the black channel (k) bits would get redistributed amongst the remaining 4 channels (CYMA) and those "new bits" added to those channels would fit in the GUID_WICPixelFormat64bppRGBA and GUID_WICPixelFormat128bppRGBA formats. But also seeing as there is no GUID_WICPixelFormat128bppRGBA format this case is kind of null and void

I basically do not understand why Microsoft says GUID_WICPixelFormat40bppCMYKAlpha and GUID_WICPixelFormat80bppCMYKAlpha should convert to GUID_WICPixelFormat64bppRGBA in the end

 

Edited by noodleBowl

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