Transparency

Transparency a quick and dirty utility for creating transparent GIF images written by Aaron Giles (giles@med.cornell.edu) version 1.0, 7 November 1994 Overview This is the first official release of Transparency, an extremely simple free utility for setting the transparency index in GIF images. Transparent GIF images are most commonly used as inline images in WWW pages, though they may have other uses as well. Transparency is shipped, like all my software, as a fat binary, running incredibly quickly on PowerPC machines. If you find any bugs or have any comments, please email me at giles@med.cornell.edu. Thank you. About GIFs GIF, or Graphics Interchange Format, is a compressed graphics format developed by CompuServe in 1987. The original specifications allowed for only simple images, but a new revision in 1989 created a host of new options for GIF images. One of these options was the ability to choose one color in the GIF's color table which maps transparently when displayed. This feature has turned out to be quite useful when used with WWW browsers which have non-white backgrounds (which is pretty much all of them anymore!) WWW Browsers with Transparent Support Just because you created a nifty new transparent GIF image doesn’t mean that it will automatically get displayed properly in all WWW browsers. Fortunately for us Macintosh users, support for transparent GIFs is already present in the latest versions of NCSA Mosaic for the Macintosh and MacWeb. Here is a brief summary of a number of WWW browers, listing those which do and do not support transparent GIFs. The following browsers support transparent GIFs: • NCSA Mosaic for the Macintosh 2.0a3, or later • NCSA Mosaic for X Windows 2.1, or later • MacWeb 1.00a2.1, or later The following browsers do not support transparent GIFs: • NCSA Mosaic for Windows 2.0a6 Design Limitations Transparency contains no features allowing you to scroll around an image; it is not intended as a -1- GIF viewer. Because it is targeted as a quick solution to setting transparent colors for WWW images, it assumes that the images it is dealing with are monitor-sized or smaller. Operation Transparency’s general operation should be pretty straightforward: you can either drag a GIF image onto the Transparency icon, or you can manually open up the Transparency application, choose Open GIF... from the File menu, and select which file you wish to work on. Transparency will then open up the image and display it onscreen for you in a window, against a gray background. To change the transparent color index, click and hold anywhere inside the image window. A small palette of the GIF’s color table will pop up, from which you can select a new transparent color or “NONE”, to disable all transparencies. (Note that if the GIF already has a transparent color selected, that color will be replaced by an “X” in the color palette.) Once you release the mouse button, the…