enum TEX_FILTER_FLAGS

TEX_FILTER_DEFAULT Default flags

Algorithm

This selects the filtering mode used for resizing and mipmap generation. In most cases it defaults to using "Fant" (aka "Box").
The legacy D3DX library implemented Point, Linear, Box, and Triangle

Dithering

This selects the use of dithering for format conversions. By default it uses no dithering.

Wrap mode

This controls how edge pixels are filtered. It defaults to CLAMP which is the only one supported by the WIC code paths. These have no impact on POINT or BOX filtering methods.

Color space

This controls color space transformation for conversions.
The sRGB color space overall is approximately equivalent to gamma 2.2. It's actually linear below a threshold, and gamma 2.4 beyond that.
http://en.wikipedia.org/wiki/SRGB

WIC usage

When both WIC-based and non-WIC based codepaths are in place, these flags can influence the standard logic choice. These are primarily used for testing and debugging purposes.
TEX_FILTER_SEPARATE_ALPHA WIC makes use of pre-multiplied alpha when resizing images, which works fine for standard transparency data. If the alpha channel, however, contains some other kind of value then the resulting image can have 'holes' in it. Use of this flag uses an alternative algorithm which resizes the RGB and alpha channels independantly and then recombines the result. This flag is not used by the non-WIC code paths, but will cause the Convert() function to use non-WIC paths.

Convert channel selection

For Convert operations, these flags control special-case logic in the non-WIC paths. Without these flags, RGB to R conversions default to converting to a luminance value and RGB to RG conversion defaults to copying the RED and GREEN channels. These are implemented in the non-WIC code paths.