Giffin  -  Sprite to GIF converter

by James Maietta

Giffin is a utility which will prove useful to anyone who needs to create GIF files for use in World Wide Web HTML documents. The GIF image format is currently the most popular format for displaying images on the World Wide Web. The main reasons for this are that GIF images can be displayed on almost every operating system used; can have transparency masks; and can be interlaced. The latter is the most important - to see an example of an interlaced GIF, look at the graphics on Acorn's home page, http://www.acorn.co.uk.

Instead of being downloaded in one go and then displayed, which can take quite some time, an interlaced GIF appears to build up on the screen while it is being downloaded, starting from a very 'low resolution' image and 'fading in' until the full image is displayed. This makes your WWW pages look more attractive and encourages the viewer to stay at your site for longer.

Giffin is a utility for creating such GIF files. It will take any 256-colour Sprite and convert it into an interlaced GIF file with a transparency mask if required. The transparency mask is pretty much identical to a mask created in Paint - the masked section will appear transparent when displayed in a WWW browser.

Note: Giffin is a front end for a command-line utility called Spr2Gif written by Simon Truss. This utility, and the other programs and documents that accompany it, can be found inside !Giffin in the GifPack directory. While you may not distribute Giffin which is copyright RISC User Magazine, the contents of the GifPack directory are in the public domain and are governed by Simon Truss's copyright licence.

Installing Giffin
Before you can run Giffin for the first time, you MUST install the Spr2Gif utility inside your Library directory. RISC PC users will find the Library directory inside the !Boot application. Other users should find the Library directory either in the root directory of the hard drive or on a system disc.

To install Spr2Gif, open the Giffin directory by holding down the Shift key and double-clicking on !Giffin in the Filer window. A window will open and you will see the GifPack directory inside it. Double-click on GifPack and then on Bin to find the Spr2Gif utility. Now open the Library directory. RISC PC users should hold down the Shift key and double-click on !Boot and then on Library. Other users should just double-click on Library.

To complete the installation simply drag Spr2Gif to the Library Filer window.

Using Giffin
To run Giffin once you have installed it, click on its icon in the RISC User menu system or double-click on its icon in the Filer window. An icon will appear on the icon bar, and you can then open the Giffin options window by clicking on this icon and then on the Sprite 2 GIF icon which appears.

The Giffin options window is divided into three sections: Reporting, GIF Format, and Transparency Settings.

Reporting
The two options in this section, Display error messages and Display progress messages, allow you to specify whether or not the Spr2Gif error and progress messages are displayed. If selected, the messages will be displayed in a Task window on the Desktop.

GIF Format
This section of the window allows you to specify whether or not the GIF image should be interlaced. If you do select the Interlaced for HTML pages option, you should also select the GIF89a format option.

Transparency Settings
This section allows you to create a GIF with no transparency mask at all; with a transparency mask created automatically from the Sprite mask; or with a transparency mask created over a specified Paint colour number. If you use a transparency mask, you must also select the GIF89a format option.

Once you have set the options, click on OK and then drag your Sprite file to the Giffin icon on the icon bar. A Save as window will open from which you can drag the GIF file to a destination Filer window

Limitations
Giffin currently only supports 256-colour Sprites. While this is a limitation of the Spr2Gif utility and not of Giffin itself, you would not make yourself popular with WWW users if you sent their phone bills rocketing by decorating your pages with loads of enormous 16 million colour images.

To generate a transparent colour with the Use sprite mask option, the colour masked in Paint must be unique; i.e. it cannot appear unmasked anywhere else in the Sprite.

GifPack contents  Copyright Simon Truss
 Copyright RISC User Magazine 1996
