Introduction

The OME image server (OMEIS) is an interface to the OME repository, where image pixels, original image files, and other large blobs are stored. OMEIS uses the file system and dynamically generated, balanced directory trees to store files and pixels (the only two BLOBs currently implemented). OMEIS can be accessed as a library, as a command-line executable or in normal use as an HTTP server. Files and Pixels are accessed using 64-bit integer IDs.

OMEIS implements a write-once strategy. File uploads are done in an atomic transaction, resulting in a read-only file on the server. Pixels are created with a NewPixels call followed by one or more methods to define their contents. Newly created Pixels are write-only until a call to FinishPixels is issued at which point they become read-only. Methods are provided to convert uploaded files to pixels, to read and write files and pixels, to convert pixels to composited images in several formats (JPEG, PNG and TIFF), and to retrieve various statistics about the pixels.

OMEIS does not parse any headers or image file formats (other than TIFF). The Convert methods are meant to be used by an external (or remote) program that understands the file format and how to extract pixels from it. Once the locations of the pixels are known in the uploaded files, the Convert calls are used to do the transfer of pixels locally to omeis. Pixels can also be written directly without Convert calls and previously uploaded files. Although OMEIS provides many useful methods relating to pixels, it is not by itself an image format converter.

OMEIS has no direct links to other components of OME, and is designed as an independent service. The single exception to this is authentication against the OME back-end. This has been designed as an easily modified component.