Exporting files to GIF and JPEG formats for use on the WWW

Gif
(Compuserve) graphics interchange format

Designed for the purpose of uploading files to online services such as Compuserve. Currently limited to 256 colors (8 bit) to reduce file size, but a 24-bit version is being implemented for the future.

Gifs (pron: "jiff") use compression techniques which were announced in early 1995 to be patented, which led to some confusion as the legality of using gifs. However, this concern seems to have passed with an agreement between Compuserve and the patent holder (Unisys).

Photoshop can open and save files as gifs. Use gifs when you have an image with sharp boundaries (eg lettering or diagrams), rather than continuous tone images (eg photos). Also useful for small file sizes compared to jpegs.

As far as the web goes, inline images are usually gifs as they are officially supported in standard HTML. A few browsers, like IBM WebExplorer and Netscape will handle inline jpegs, but this is not standard (yet).

To save in Photoshop you must set the mode to "indexed color." CMYK or RGB modes will not allow you to save as a gif. This is due to the fact that gifs are only 8 bit.

Jpeg
Joint Photographic Experts Group

Supports many more colors than gifs (at least 24-bit or 16.7 million). Uses lossy compression, so that every time you close a jpeg and reopen it you lose data. This is called a cumulative compression scheme. You can, however, save repeatedly to disk in a single session as the jpeg always works from the on screen version.

As mentioned above, jpegs work best for continuous tone images (where the distinction between neighboring pixels is slight).

Pshop allows you to select how much data is lost during compression. Saving an image at "maximum image quality" loses the least data but results in highest file size. Saving at "lowest image quality" does the opposite; a lot of data is lost, for a small file size.

Tiff
Tag image file format

Perhaps the most widely supported cross-platform format, it was developed in the days of the early Macintoshes by Aldus. Pshop allows you to save tiffs for the PC or the Mac during the saving process.

Tiff uses a lossless compression scheme known as LZW, the same method as used in the gif file. Unlike gifs though, tiff can support more than just the indexed color mode. Freehand can handle tiffs with LZW compression.

---

Q: Which is better, gif or jpeg?
A: It really depends. Small file size = gif. 24 bit image = jpeg. Compression in gifs = lossless. Compression in jpegs = lossy.
Additionally, gifs can be made transparent and interlaced, whereas jpegs can't.

Q: Ok, so is tiff better then?
A: Sheesh!

Exporting to GIF format from Corel*Draw:

Follow these steps to create a GIF file from a Corel*Draw .cdr file:

1. Save the drawing as graphic.cdr
2. Under the File menu, select "Export"
3. Under "List files of Type" choose CompuServe Bitmap, *.gif
4. select the destination directory and filename, then click OK
5. In the "export" window,select color, dithered colors, 256 colors, 75dpi resolution, and 1:1 size

Exporting to JPEG format from Corel*Draw:

Follow these steps to create a JPEG file from a Corel*Draw .cdr file:

1. Save the drawing as graphic.cdr
2. Under the File menu, select "Export"
3. Under "List files of Type" choose JPEG BITMAP *.jpg
4. select the destination directory and filename, then click OK
5. Use the default JPEG Format and Subformat options. Move the slider bar to select the amount of compression you want. More compression means a smaller file, but also diminished file quality. Click on OK.
6. In the "export" window,select color, 16 million colors, 75dpi resolution, and 1:1 size

Exporting to GIF format from Adobe Photoshop:

1. Save the drawing as graphic.psd
2. Under the Mode menu, select Indexed Color
3. In the window that appears, select other for the resolution and type 256 in the "colors" box. Select Adaptive Palette and either None or Diffusion (your choice) for the Dither mode. Click OK.
4. Now, select File, Save As, and Compuserve *.GIF as the format type. Enter your file name in the appropriate box, and click on OK.

Exporting to JPEG format from Adobe Photoshop:

Make sure you only have one layer in your graphic. If you've been working with multiple layers (to add text, for instance), you should use the Merge Layers or Flatten Image command on the layers control window.

Select "Save as" from the File pull-down menu and choose "jpeg" as the file type.