Creating Transparent Graphics
One of the best advantages of PowerPoint is its ability to import dozens of different graphic types. While each format has its pros and cons, one of the biggest advantages of the GIF (pronounced “gif,” not “jif”) and PNG (“ping”) formats is their ability to display transparent data. In other words, they can be cut-out shapes with no background color, so a soccer ball can be a round ball and not a white square with a picture of a ball in the middle.
Despite this common trait, the GIF and PNG formats are wildly different. GIF was first on the scene years ago, and was developed by CompuServe as a display format. GIF supports 1-bit transparency, meaning pixels are either completely visible or completely invisible, with no middle ground. GIF images often have “jaggies” around the edge as graphic programs try to guess which pixels should be on and which should be off. (This is demonstrated in the image below and the included PowerPoint file.)
PNG is an open-source format that supports 8-bit transparency. This enables 256 stages of transparency, so anti-aliased edges are soft, and fades can be easily achieved. Please refer to the graphic below for a clear example of the difference.
Both of these are easy to create in PhotoShop. Design your image, and leave the background layer off, so the plain, checkered background shows through. This tells PhotoShop that the image is not solid, and that it will need to accommodate transparency information when you save.
Go to File > Save For Web, and in the right-hand palette in the new window, choose either GIF or PNG-24. PNG-8 only supports 1-bit transparency, same as GIF, so there is no advantage with that format. JPEG, while generally good for photographs and other color-rich images, does not support any degree of invisibility.
Hit “Save,” give it a name and a home, and then import the graphic into PowerPoint like normal. That’s it! 99% of the time, saving to PNG is the best option. The file size is about the same, and the advantages of complete transparency are numerous. GIF is an older format that is becoming long in the tooth. The only advantage it still holds is the ability to contain animation information, but that will eventually change in the future as the PNG format matures and is able to provide the same level of interactivity.