Image file directory (TIFF)

The image file directory for TIFF will contain a selection of the following entries:

• File Byte Order: OS defaults to the use of MM = Motorola Byte Order; the order in which the data is interpreted.

• Tag 256 (ImageWidth): The number of columns in the image, i.e. the number of pixels per row, for example, value = 4000.

• Tag 257 (ImageLength): The number of rows of pixels in the image, for example, value = 4000.

• Tag 258 (BitsPerSample): The number of bits per component, for example, value = 8.

• Tag 259 (Compression): Compression scheme used on the image data, for example, value = 5 (LZW).

• Tag 262 (PhotometricInterpretation): The colour space of the image data, for example, value = 3 (Palette).

• Tag 270 (ImageDescription): A string that describes the subject of the image, for example, value = 1:25 000 TILE SU41.

• Tag 273 (StripOffsets): For each strip, the byte offset of that strip, for example, first four values = 5640 19678 35692 51409.

• Tag 277 (SamplesPerPixel): The number of components per pixel.

• Tag 278 (RowsPerStrip): The number of rows in each strip, for example, value = 8.

• Tag 279 (StripByteCounts): For each strip, the number of bytes in that strip after compression, for example, first four values = 14038 16014 15717 15442.

• Tag 282 (XResolution): The number of pixels per Resolution Unit in the Image Width, for example, value = 254.

• Tag 283 (YResolution): The number of pixels per Resolution Unit in the Image Length, for example, value = 254.

• Tag 284 (PlanarConfiguration): Look-up table, for example, value = first four values = 22873 31354 39321 59110.

• Tag 296 (ResolutionUnit): How the components of each pixel are stored. Default value is ‘2’ (inch).

• Tag 306 (DateTime): Date and time of image creation, for example, value = 2007:06:30 12:38:41.

• Tag 317 (Predictor): A mathematical operator that is applied to the image data before an encoding scheme is applied.

• Tag 320 (ColourMap): Look-up table, for example, value = first four values = 22873 31354 39321 59110.

• Tag 339 (SampleFormat): Specifies how to interpret each data sample in a pixel.

• Tag 33432 (Copyright): Copyright notice, for example, value = ORDNANCE SURVEY CROWN COPYRIGHT 2019.

The preceding values are relevant to 1:25 000 scale TIFF data with LZW compression.