Here's a handy little utility which allows you to produce those nice interlaced gifs as are becoming more popular now, thanks to Netscape et al.
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WebGif2 is based on the work of <a href="tom">Tom Boutell</a>, notably the excellent <i>gd</i> library, with which webgif was written (originally under UNIX :) Anyone wanting to handle GIFs easily in their own code should have a look at this library (I can supply Arc-friendly code..) I have produced an interactive clickmap creator for my www cgi-bin directory; its so fast and easy!
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<h2>Using WebGif2</h2>
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WebGif2 can work in two 'modes': Batch or Interactive:<p>
<b>Interactive Mode</b><p>-
This is the default mode. When you drag a Sprite or GIF file to the WebGif2 icon on the iconbar, it will be decoded and a window will open containing a quick preview of the image. Below this window you will see a toolbox. The right hand side of this toolbox allows you control various aspects of the output:<br>
<p><b>Interlace</b><br>
An interlaced GIF image is stored in the file in such a way that when a very small part of the data has been downloaded you can get a rough idea of the image. As more data is downloaded, the image becomes sharper. This has a very pleasing effect on web pages, especially on larger images. If the 'Interlace' icon is selected then the GIF will be saved in this way, if not, all the data is store sequentially and the image will just build-down from the top.
<p><b>Mask</b>
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In a GIF image, a single colour may be defined to be 'transparent' so that when the image is plotted, the image benath the transparent area is unaffected. In this way you can create the illusion of non-rectangular images which greatly improves the appearance of web pages.<br>
When the 'Mask' icon is selected, the colour displayed to the right of this icon will be used as the transparent colour. If you do not want a transparent colour, just deselect 'Mask'<br>
To choose which colour you would like to appear as transparent, simply click on the area of interest in the image preview. This window can be dragged out larger if you require, to allow you to more easily 'hit' the required colour pixel. Alternatively, if you already know the exact colour number that you require, you may enter it in the icon on the extreme right of the toolbox and then press 'Enter'. The small coloured block on the toolbox will change colour to <b>approximately</b> the colour of the transparent area in the GIF.
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Once the Interlace and Mask options have been set, you can save out the new image by using the two save icons on the left of the toolbox. These represent GIF and Sprite image respectfully and this area works fairly much like a standard RISC OS save dialogue. Simply enter a new filename in the lower icon, and then drag either GIF or Sprite icon to a filer display window, depending on the type of image you wish to create.<br>
Please note that I have not had the time to create masked sprite saving, so the mask (and obviously the interlace) values will be ignored when saving as a sprite. This holds true for loading too. If enough people would like this functionality I may be persuaded to add it.
<p><b>Batch Mode</b><p>
To use WebGif in this mode, you must select the 'Same Filename' icon on the iconbar options submenu. Once selected, set up the rest of the options in this dialogue as described above. You can now drag files in to WebGif2 and they will NOT be displayed in a window, instead they will be processed with the options you defined and saved <b>with the same filename</b> (ensure you have copies of original sprites if required!!). This allows you to set Interlace, Mask etc on a large number of files as easily as possible.<br>
I would <b>NOT</b> recommend this mode of operation for normal use as it can easily lose your orginal sprite data!!
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<h2>Limitations</h2>
WebGif2 can load 2,4,8,16 and 256 colour RISC OS sprites and all formats of 'GIF' files. It can save as either an 256 colour RISC OS sprite, or a GIF file.<br>
Most common usage will be loading 256 colour sprites and saving GIFs<br>
Note that when in batch mode, the image is <b>always</b> saved as a GIF
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<h2>Tips</h2>
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<li>Small inline GIFs are better left un-interlaced (turn off the <i>Interlace</i> icon)
<li>If you dont want <b>any</b> colour to be transparent, ensure the <i>Mask</i> icon is off.
<li>Images produced with <i>ArtWorks</i> etc, or with aliased fonts can be well presented in <i>Netscape</i> if you use the aliasing to your benefit: Create files with a wimp colour 1 background (20% Grey in ArtWorks)<br>Then use !Paint to flood fill (locally!) the outer grey areas of the image with some unused colour (eg bright magenta!) Use this colour as the transparency colour and you will find that when the image is displayed, it is nicely aliased to the window background colour. This is better than using a (eg magenta) background colour to aliase on to from the start, as it would otherwise produce strange coloured aliased edges!!
<li>Remember that WebGif2 can also <b>remove</b> a transparency mask and/or interlacing; just run the file through WebGif2 again if you dont like the output :)
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<h2>Versions</h2>
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<b>1.00</b> First version, released to a few people<p>
<b>1.10</b> Fixed menu code and added ability to use transparency from source<br> <i>(Thanks BjD!)</i><br>
Added ability to define the default transparency colour (in the <i>Messages</i> file!!)<p>
<b>2.00</b> Completely recoded as one piece of C. !Boot file now aliases 'webgif' to call the program's !RunImage. Only when -desktop is the first parameter will the WIMP frontend be invoked. This all adds up to WebGif2 being even more flexible and much faster than before.<br>
Added <i>point'n'click</i> interface for previewing the GIF and selecting the transparency colour. Also allows sprites to be <b>loaded</b> and saved.<p>
<b>2.10</b> Added HTML tag generation and ability to load 256-palette-entry sprites.<p>
<b>2.20</b> Test StrongARM version<p>
<b>2.30</b> Official StrongARM release. Thanks to <i>Oregan</i> for lending me a RiscPC.<br>
<h2>Contacts</h2>
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If you find some bug (I hope not!) or if you just want to tell me what you think of this program, please contact me at the following:<p>
Many hours have been spent working on this program. Hopefully you will find it useful. Any contributions received will be put towards the Riscy Developments' Hardware fund. (Nothing recieved so far) This fund aims to buy a reliable monitor for Ian Jeffray...<br>
<h2>Contributors</h2>
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WebGif2 was written by Ian Jeffray of Riscy Developments. The WebGif core library was originally written for UNIX and has had <a href="Contribute"><b>many</b> people</a> contributing to it. My thanks go to all of these people for spending time to create such a useful program and libraries. FreeWare still lives on strong. Long live GNU!
