This enumeration determines the edge of the "paper" with which the image's "top" is aligned.

Values:

IG_TW_OR_LANDSCAPE	Equals IG_TW_OR_ROT270.
IG_TW_OR_PORTRAIT	Equals IG_TW_OR_ROT0.
IG_TW_OR_ROT0	Normal orientation.
IG_TW_OR_ROT180	Rotated 180 degrees clockwise.
IG_TW_OR_ROT270	Rotated 270 degrees clockwise.
IG_TW_OR_ROT90	Rotated 90 degrees clockwise.