The image server digilib is a state-less web-based client-server application for interactive viewing and manipulation of images.
digilib consists mainly of two parts, the image server component proper, called “Scaler” and a client-side part that runs in the users web browser.
The users browser sends an HTTP request for a certain (zoomed, scaled, rotated) image to the Scaler server and the server returns the image data as HTTP response.
The frontend-server and the Scaler-server do not have to run on the same machine and often there are several frontends that use the same Scaler server.
The Scaler API is documented on the digilib.sourceforge.net pages. Here is a minimal version:
The Scaler servlet takes parameters in the HTTP request format: Scaler?param1=value1¶m2=value2&... Unknown parameters will be silently ignored.
The image will be scaled equally in horizontal and vertical direction such that the resulting image does not exceed the rectangle [dw,dh]. If only either height or width is given the image is scaled to match only the given parameter. The size of the resulting image in the other parameter is determined by the aspect ratio of the image.
An example for a Scaler URL is: http://digilib.mpiwg-berlin.mpg.de/digitallibrary/Scaler?fn=experimental/digilib-test/images&wh=0.1712&ww=0.1282&wy=0.1681&wx=0.6895&dw=862&dh=904 such a URL can be used as src attribute to an img element in the frontend HTML.