Xres TechNote

Shockwave for xRes

Objective
Shockwave for xRes enables users to view, pan, and zoom large image files on the web quickly, based on xRes technology. Shockwave for xRes is basically a CGI script for Windows NT and Unix web servers that is available free for downloading in the Macromedia Developers Center. The Mac plug-in and Afterburner are available for end users; however, Mac web servers are not supported yet. The CGI scripts for Macintosh web servers and Windows 95 web servers are still under development. Microsoft Internet Explorer is currently not supported. Considering the fact that this is a beta plugin, there is no direct support from Macromedia Technical Support, and the user must rely on the information available on the web.

Shockwave for xRes functions:

Magnifying Glass
This tool zooms in and out of a point on the image by powers of 2 by clicking the magnifying glass cursor on the desired point. The resulting view will be centered on that point. The appropriate keyboard key will be pressed to signify zooming out.

Rectangular Selection
This tool is an alternative way to select a view of the image by dragging a rubber band rectangle at the desired location. The dragged rectangle maintains the aspect ratio of the viewing window. The resulting view shows the nearest power of 2 magnification of the image that contains the selected area.

Panning Tool
This tool provides panning about the image at the selected magnification level. The user drags the panning cursor in the direction and distance that he or she wishes the underlying image to move. A low-res image will be displayed live while panning and the desired resulting view will be shown when the mouse button is released.

Shockwave for xRes components:

	Afterburner.
	The CGI script that goes on the server.
	A Netscape plugin to interface between the web document and the CGI script.

Afterburner
The images to be read on the web by this plugin will need to be in new format based on the xRes LRG format. The LRG format recomposes a large bitmap image into seven different levels of resolution (zoom). The plugin will request one tile's worth of data at a time from the web document.

CGI Script
The CGI script is based on xRes technology modified to allow recomposing images into tiles of arbitrary sizes and it goes on the server, not on your desktop machine. Shockwave for xRes allows the tile color components to be planar, interlaced, or indexed.

Netscape Plugin
The Netscape plugin defines the interface between the web document and CGI Script. It will send requests for image data to the web document and read the data coming back. It will also interpret mouse events that concern the graphics engine.

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