Graphics Tools for Linux
Programming interfaces aren't really end-user tools, but I'd like to mention a few, since these interfaces are likely to be the basis of the next generation of end-user tools.
One of the most popular and widespread programming interfaces is OpenGL, from Silicon Graphics. OpenGL is a hardware-independent programming interface that provides commands and operations to produce 3D, interactive applications. This technology is fairly new and requires support in your X server to make use of hardware accelerations provided by video adapters. Although the hardware support is not required in order to use OpenGL, without it or a relatively fast computer, OpenGL applications will run a bit sluggishly. A freely available version of OpenGL, known as MesaGL, implements most (if not all) of the OpenGL command set. Also, OpenGL has a very low level interface, much like Xlib is to X-Windows; therefore, higher level toolkits, such as GLUT or aux, are more appropriate for writing applications. [For more information on OpenGL/Mesa, see Linux Goes 3D elsewhere in this issue—ED.]
VRML is the Virtual Reality Modeling Language, designed to provide a 3D interface using a markup language similar to HTML. The current VRML 2.0 specification is based on Silicon Graphics Moving Worlds specification. Only a few VRML-capable browsers are available; however, there is strong industry interest in this language, and I expect many browsers will be supporting it in the near future. A recent report by C|Net cited both Netscape 3.0 and MS Internet Explorer as supporting VRML to some degree.
A number of other programming libraries have been announced on the comp.os.linux.announce newsgroup:
SRGP - the Simple Raster Graphics Package, a toolkit for use with Computer Graphics: Principles and Practice, 2nd Edition, by Foley, van Dam, Feiner and Hughes.
lib3d - an X-based 3D rendering library
EZWGL - a Motif-like widget library that includes some GL support
YGL - emulates SGI's GL (Graphics Language) under X11
As I mentioned earlier in this article, web browsers support the GIF image format, and some JPEG; most now support both formats. In choosing one of these formats, you should consider the following:
How big is the image in bytes?
Do you want the outline of the image to be visible or do you want the background to show through?
Do you want the image to fade into view while the surrounding text is displayed, or do you want the image displayed before the text?
The answers to these questions help determine which image format to use. JPEG will usually compress images without losing too much of the information and appearance of the image, than GIF. Therefore, if your images take up a lot of disk space (a problem since my ISP doesn't provide much disk space for private web pages), or you don't want to force your readers to download large images, JPEG images would probably be better. However, if your image has a background you do not want displayed but you do want the background image or color of the page to show through, you need to use GIF-formatted images, as JPEG does not provide transparency in images.
If you want your images to fade into view as the text around it is displayed, you need to use GIF images. This trick is called interlacing, and JPEG does not support it. If you have large images (not necessarily in bytes, but ones that take up a lot of screen space), it is more user-friendly to use interlaced GIF images.
Once you've decided on the type of images you'll use, you can start creating them. There are many tricks and tips, but for starters I suggest you get hold of the following tools:
You can use these tools, along with a CD-ROM of images (readily available from computer software stores) to create your own little web world. When you get adventurous, you might try adding some complex 3D images using POV-Ray. If you're interested in using special fonts with the GIMP, I suggest looking for packages containing Adobe Type 1 fonts. Once you have these you should check out the typ1inst package, which will allow you to install the fonts for use with your X server.
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