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Baseline TIFF Tag Orientation

TIFF Tag Orientation

IFDImage
Code274 (hex 0x0112)
NameOrientation
LibTiff nameTIFFTAG_ORIENTATION
TypeSHORT
Count1
Default1

Description

The orientation of the image with respect to the rows and columns.

The specification defines these values:

1 = The 0th row represents the visual top of the image, and the 0th column represents the visual left-hand side.
2 = The 0th row represents the visual top of the image, and the 0th column represents the visual right-hand side.
3 = The 0th row represents the visual bottom of the image, and the 0th column represents the visual right-hand side.
4 = The 0th row represents the visual bottom of the image, and the 0th column represents the visual left-hand side.
5 = The 0th row represents the visual left-hand side of the image, and the 0th column represents the visual top.
6 = The 0th row represents the visual right-hand side of the image, and the 0th column represents the visual top.
7 = The 0th row represents the visual right-hand side of the image, and the 0th column represents the visual bottom.
8 = The 0th row represents the visual left-hand side of the image, and the 0th column represents the visual bottom.

The specification considers this a baseline tag, but does add that support for orientations other than 1 is not a Baseline TIFF requirement.

LibTiff defines these values:

ORIENTATION_TOPLEFT = 1;
ORIENTATION_TOPRIGHT = 2;
ORIENTATION_BOTRIGHT = 3;
ORIENTATION_BOTLEFT = 4;
ORIENTATION_LEFTTOP = 5;
ORIENTATION_RIGHTTOP = 6;
ORIENTATION_RIGHTBOT = 7;
ORIENTATION_LEFTBOT = 8;

Many readers ignore this tag.

The DNG specification makes this tag mandatory, rather then optional. This has benefits in that lossless rotation of IFDs in compliant DNG files can be achieved by changing a single byte value in the file, instead of having to rewrite a complete extended IFD.