Leica format

single-file pyramidal tiled BigTIFF with non-standard metadata
File extensions
OpenSlide vendor backend


Leica slides are stored in single-file BigTIFF format. OpenSlide will detect a file as Leica if:

  1. The file is TIFF.
  2. The initial image is tiled.
  3. The ImageDescription tag contains valid XML in either of these namespaces:
    • http://www.leica-microsystems.com/scn/2010/03/10
    • http://www.leica-microsystems.com/scn/2010/10/01

Relevant TIFF tags

Tag Description
ImageDescription Stores an XML document containing various metadata

File Organization

The ImageDescription tag of the first TIFF directory contains an XML document that defines the structure of the slide.

Leica slides are structured as a collection of images, each of which has multiple dimensions (pyramid levels). The collection has a size, and images have a size and position, measured in nanometers. Each dimension has a size in pixels, an optional focal plane number, and a TIFF directory containing the image data. Fluorescence images have different dimensions (and thus different TIFF directories) for each channel. OpenSlide currently rejects fluorescence images and ignores focal planes other than plane 0.

Brightfield slides have at least two images: a low-resolution macro image and one or more main images corresponding to regions of the macro image. The macro image has a position of (0, 0) and a size matching the size of the collection. Fluorescence slides can have two macro images: one brightfield and one fluorescence.

The slide provides enough information to composite the various images, including the macro image, into a single pyramid. However, there are some complications:

Thus, in general, the images in a collection cannot be rendered into a unified pyramid without scaling the original pixel data. OpenSlide does not attempt to do this. Instead, OpenSlide omits the macro image from the pyramid and refuses to open slides whose main images have inconsistent resolutions.

Associated Images

the highest-resolution dimension of the macro image

Known Properties

the numericalAperture of the main image
the barcode text. (For slides in the 2010/10/01 namespace, OpenSlide 3.4.0 and earlier report this property as a Base64-encoded string; OpenSlide 3.4.1 and later report it in plain text. For slides in the 2010/03/10 namespace, OpenSlide reports the barcode as it is stored in the XML, since we do not know whether those barcodes are Base64-encoded. If you have a 2010/03/10 slide with a bar code, please comment in this bug or contact the OpenSlide mailing list.)
the creationDate of the main image
the device model of the main image
the device version of the main image
the illuminationSource of the main image
the objective of the main image
calculated as 10000/tiff.XResolution, if tiff.ResolutionUnit is centimeter
calculated as 10000/tiff.YResolution, if tiff.ResolutionUnit is centimeter
normalized leica.objective

Test Data