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OpenSlide Java version 0.13.0, 2024-05-04

OpenSlide Java 0.13.0 requires Java ≥ 22 and OpenSlide ≥ 4.0.0, switches from JNI to FFM so OpenSlide Java builds are platform-independent, adds support for OpenSlide 4.0.0 features, and switches the build system to Maven.

Binary build removes OpenSlide Java.

Binary build, 2024-03-29

Binary build adds Linux and macOS binaries, removes 32-bit Windows binaries, and adds Python binary packages for use with the upcoming OpenSlide Python 1.4.0. It also updates OpenSlide Java to 0.12.4 and updates various dependencies.

OpenSlide Java version 0.12.4, 2023-11-07

OpenSlide Java 0.12.4 includes minor build and test improvements.

Fedora and Enterprise Linux Copr now available, 2023-10-11

OpenSlide now provides a Fedora Copr, enabling users of Fedora and RHEL-compatible enterprise Linux to easily install the latest OpenSlide and OpenSlide Python releases before they reach Fedora or EPEL.

OpenSlide version 4.0.0, 2023-10-11

OpenSlide 4.0.0 adds support for DICOM WSI slides, ICC color profiles, tile cache customization, adds the slidetool command-line utility, removes deprecated APIs, and improves format compatibility.

Windows build 20231011 integrates all dependencies into the OpenSlide DLL, replaces the separate command-line tools with slidetool, and switches from MSVCRT to the Universal C Runtime (UCRT).

Ubuntu PPA now available, 2023-10-11

OpenSlide now provides an Ubuntu PPA, enabling Ubuntu users to easily install the latest OpenSlide and OpenSlide Python releases before they reach Ubuntu.

OpenSlide Python version 1.3.1, 2023-10-08

OpenSlide Python 1.3.1 updates the docs and example tools to transform images to sRGB using the default rendering intent of the image’s ICC profile, rather than absolute colorimetric intent.

OpenSlide Python version 1.3.0, 2023-07-22

OpenSlide Python 1.3.0 adds support for the upcoming OpenSlide 4.0.0 and drops support for Python 3.7. It also exposes color management profiles where available, and updates the Deep Zoom example tools to transform images to sRGB by default.

Older news is available here.

OpenSlide is a C library that provides a simple interface to read whole-slide images (also known as virtual slides). The current version is 4.0.0, released 2023-10-11.

Python and Java bindings are also available. The Python binding includes a Deep Zoom generator and a simple web-based viewer. The Java binding includes a simple image viewer.

OpenSlide and its official language bindings are released under the terms of the GNU Lesser General Public License, version 2.1.


About OpenSlide

The library can read virtual slides in the following formats:

It provides a simple C interface for programmers to use to decode images of these kinds.

OpenSlide’s support for these formats is not endorsed by their respective vendors and may be incomplete. Problems should be reported to the OpenSlide mailing list or issue tracker.

OpenSlide is a product of the research group of M. Satyanarayanan (Satya) in the Carnegie Mellon University School of Computer Science.

See how some projects use OpenSlide.


There is a web-based demo of OpenSlide rendering various slide formats.


Getting Help

First, try the search box at the top of the page. It covers the OpenSlide website, mailing list, issue tracker, and wiki.

Questions should be sent to the users mailing list. If you think you have found a bug, please report it in the appropriate issue tracker.

Mailing Lists

There are two mailing lists for OpenSlide:


Some developer documentation is available:

Development of OpenSlide happens on GitHub:

Test Data

Some freely-distributable test data is available.


The design and implementation of the library are described in a published technical note:

OpenSlide: A Vendor-Neutral Software Foundation for Digital Pathology Adam Goode, Benjamin Gilbert, Jan Harkes, Drazen Jukic, M. Satyanarayanan Journal of Pathology Informatics 2013, 4:27 HTML

There is also an older technical report:

A Vendor-Neutral Library and Viewer for Whole-Slide Images Adam Goode, M. Satyanarayanan Technical Report CMU-CS-08-136, June 2008 Computer Science Department, Carnegie Mellon University Abstract PDF

About whole-slide images

Whole-slide images, also known as virtual slides, are large, high resolution images used in digital pathology. Reading these images using standard image tools or libraries is a challenge because these tools are typically designed for images that can comfortably be uncompressed into RAM or a swap file. Whole-slide images routinely exceed RAM sizes, often occupying tens of gigabytes when uncompressed. Additionally, whole-slide images are typically multi-resolution, and only a small amount of image data might be needed at a particular resolution.

There is no universal data format for whole-slide images, so each vendor implements its own formats, libraries, and viewers. Vendors typically do not document their formats. Even when there is documentation, important details are omitted. Because a vendor’s library or viewer is the only way to view a particular whole-slide image, doctors and researchers can be unnecessarily tied to a particular vendor. Finally, few (if any) vendors provide libraries and viewers for non-Windows platforms. Some have gone with a server approach, pushing tiles through a web server, or using Java applets, but these approaches have shortcomings in high-latency or non-networked environments.


OpenSlide has been supported by the National Institutes of Health and the Clinical and Translational Science Institute at the University of Pittsburgh.

Development of DICOM and ICC functionality was supported by NCI Imaging Data Commons and has been funded in whole or in part with Federal funds from the National Cancer Institute, National Institutes of Health, under Task Order No. HHSN26110071 under Contract No. HHSN261201500003l.