Convert to sRGB color space on load

[walbourn]

Currently when loading WIC files we use explicit sRGB metadata to distinguish between 'normal 'and 'sRGB' formats. There's also a flag to ignore this metadata.

When loading images, however, some contain additional color information that can be used to convert to sRGB formats.

[walbourn]

Hi,

Attached is a patch of something I added locally to DirectXTex that was helpful for my specific use case and I'm passing it along in case you are interested. It adds a WIC_FLAG for loading source images using WIC that are known to contain color data, and will use WIC color contexts to convert the source data to sRGB (and also assumes source image data to be sRGB when no color contexts exist).

In our application we allow users to load any images that they want, but I want the generated DDS files that will be used as the actual color textures to be sRGB. The existing LoadFromWIC functions handle the case when an image explicitly says that it's sRGB, but I couldn't discover a way to differentiate between when an image was implicitly sRGB and when it was explicitly non-sRGB (e.g. using Adobe RGB).

If this change is interesting to you feel free to modify/improve it as you see fit. (I tried to match the existing style, but I probably made some decisions that are sub-optimal hehe.)

John-Paul