Trestle slides are stored in single-file TIFF format. OpenSlide will detect a file as Trestle if:
Softwaretag starts with
ImageDescriptiontag is present.
||Stores some important key-value pairs, see below|
||Starts with “
||Seems to store microns-per-pixel (MPP), which may or may not take into account the correct objective power. Note that this is inverted from standard TIFF, which stores pixels-per-unit, not units-per-pixel.|
ImageDescription tag contains semicolon-delimited key-value
pairs. A key-value pair is equals-delimited. We use the
Background Color keys from the
ImageDescription, and ignore
the rest. All of these values are stored as properties starting with
||Hex-encoded background color info, assumed to be in the format
||Hex-encoded white balance|
||Reported objective power, often incorrect.|
||The JPEG quality value.|
||Overlaps, see below.|
The first image in the TIFF file is the full-resolution image. The subsequent images are assumed to be decreasingly sized reduced-resolution images.
OverlapsXY pseudo-field encodes a list of tile overlap values as
64 64 32 32 16 16” (note the initial space).
These values represent the standard overlaps between adjacent tiles in X and Y, in pixels. This example encodes 3 levels worth of overlaps. Further overlaps are assumed to have the value 0.
Individual tile overlaps may differ from the standard overlaps. These
individual overlaps are recorded in
.tif-Nb files adjacent to the
N is the level number. OpenSlide does not read these files,
though they have been partially decoded; see issue 21 for
All data encoded in the
ImageDescription TIFF field is represented
as properties prefixed with “
tiff.XResolution(note that this is a totally non-standard use of this TIFF tag)
tiff.YResolution(note that this is a totally non-standard use of this TIFF tag)