Size does matter
When choosing images for use on Palm devices, it's important to remember the size of the display. For example, the actual size of the Palm connected organizer screen is 160x160 pixels. Once the screen is painted with the title bar and scroll bar, you are left with a usable area that is approximately 150 pixels wide and 140 pixels tall. However, if you attempt to display an image that is wider than 150 pixels, some software can scale it to fit inside the viewing area. Scaling reduces the quality of many images, so you generally should avoid using images wider than the Palm device's viewing area. Use "large" images sparingly and only when appropriate, as they not only consume screen real estate, they consume synchronization bandwidth.

Consider the details
If the image is wider than 150 pixels and somewhat complicated, the scaling operation may obscure critical information. Therefore, it's good practice to avoid large, detailed images. If there is a convenient way to convey the same information without using an image, you are probably better off dispensing with the image. If you must use detailed images, you should tailor them especially for the device in order to achieve a predictable result.

Choose contrasting colors
The original color scheme of an image also plays an important role in the way it is rendered on the handheld. For example, the process AvantGo employs is to convert color images to black and white ones on images that have a high contrast ratio between colors and that have crisp edges in the details of the picture. Images that are anti-aliased, or smoothed out, do not usually convert well. It is usually a good idea to stick to graphics that are primarily black-and-white when using Palm OS devices, as it can be hard to predict how dark certain colors will turn out. You should also try to avoid graphics with lots of curved lines.

Design your own images
The easiest and most predictable way of deploying images on Palm devices is to make your own custom bitmapped images. For the Palm devices, they should be 150 pixels wide or less, so that the software doesn't have to covert or resize them at all. You can create and edit such images with most image-editing packages. If you are used to working with large full-color images, it might seem rather restrictive, but it's not as limiting as you might think. It's also good practice to design your images with clean lines and simple shapes since more complicated elements tend to appear ragged. In other words, it is better to use an image that is deliberately simple, rather than to try using a complex image that looks confusing. Keep in mind what's appropriate for the medium. If you want to look at high-resolution images, save them for the desktop and reserve the handheld for less graphical information.

[Here's an interesting "retro" idea. If you know someone who's done graphics for the original, black-and-white Macintosh machines, consider recruiting that person to help you with designing images for the Palm display. It sure beats an old-folks home. -- DG]