This enumeration specifies the kind of JPEG quantization tables that tradeoff quality versus compressed image size.

Values:

IG_TW_JQ_HIGH	Write-only; implies high quality; the images display the maximum quality that produces any kind of meaningful compression. Note that images at this setting are still considered to be lossy.
IG_TW_JQ_LOW	Write-only; implies low quality; the images are at the maximum compression recommended by the Source.
IG_TW_JQ_MEDIUM	Write-only; implies medium quality; the images are at the balance point between good compression and good images. This is an arbitrary setting on the part of the Source writer that is expected to best represent their device. This is the value that Applications are most encouraged to use.
IG_TW_JQ_UNKNOWN	Read-only; must be the setting for this capability if the user sets the JPEG compression tables using DAT_JPEGCOMPRESSION, and the Source is not able to map the selected tables to a specific percentage of quality.