使用 WIC 在 DirectX11 中将纹理加载为 RGB 而不是 sRGB

Question

I'm loading textures using CreateWICTextureFromMemoryEx from DirectXTK . Everything I load is converted to sRGB . Is there any way to force WIC to create RGB surface instead?

Or maybe there is a way to convert an already loaded texture from sRGB to RGB ? Back in D3DX there used to be D3DX11_FILTER_SRGB flag for that (from what I understand) but it's not deprecated.

Any help will be very appreciated, thanks!

Answer 1

The DirectX Tool Kit loader uses DXGI_FORMAT_*_SRGB when loading WIC images for a few reasons:

• The WIC metadata for a PNG file contains the sRGB chunk ( /sRGB/RenderingIntent is true)

• The WIC metadata for a JPG indicates sRGB ( /app1/ifd/exif/{ushort=40961} is 1)

• The WIC metadata for a TIFF indicates sRGB ( /ifd/exif/{ushort=40961} is 1)

• If you pass 'true' as the forceSRGB parameter to the Ex version of the function

So the image is in fact likely in sRGB colorspace. Therefore, the DXGI_FORMAT_*_SRGB indicates that reads from that texture should be subject to de-gamma to get them into a linear colorspace. I'm assuming you are not using gamma-correct rendering here?

Gamma-correct rendering is achieved by using a DXGI_FORMAT_*_SRGB or HDR (10:10:10:2, 16:16:16:16) backbuffer format. You also need to use linear colors for Clear . See DeviceResources , Gamma-correct rendering , The Importance of Being Linear , and Linear-Space Lighting (ie Gamma) for details.

A quick and easy workaround if you control the texture file would be to use texconv in the DirectXTex library to convert the source image to a DDS . You can use various switches like -srgbi or -srgbo to force the SRGB behavior you are after.

Note that I'm also adding an option to let you ignore the sRGB metadata when using WICTextureLoader for a future release of DirectX Tool Kit . Linear rendering is best, but sometimes it's nice to have the option to avoid the DXGI_FORMAT_*_SRGB format being used.