Unit of resolution measurement. 0x0128 ∙ 296

IG_ISIS_TAG_RESUNIT contains the unit of measurement for XResolution and YResolution.

Type:

IG_ISIS_TAG_TYPE_SHORT

Drivers:

PIXFPACK. Note that resolution for ISIS drivers is always specified in dots per inch.

Values:

Value	Defined Constant	Meaning
1	IG_ISIS_RESUNIT_NONE 1	No absolute unit of measurement. Used for images that may have a non-square aspect ratio, but no meaningful absolute dimensions.
2	IG_ISIS_RESUNIT_INCH	Resolution is specified in dots per inch.
3	IG_ISIS_RESUNIT_CENTIMETER	Resolution is specified in dots per centimeter.

The default value is 2 (IG_ISIS_TAG_RESUNIT_INCH).

The drawback to this value is that different applications will import the image at different sizes. Even if the decision is arbitrary, it might be a good idea to use dots per inch or dots per centimeter, and to pick XResolution and YResolution so that the aspect ratio is correct and the maximum dimension of the image is about an arbitrary four inches.