One important issue to consider when creating graphic images is how the pictures will appear on different video displays. Help can display graphics on computers with many different kinds of video hardware, including the most common display types—monochrome, color, EGA, VGA, and 8514. When you prepare pictures for Help, you should analyze the target audience for the Help file and determine what percentage of that audience has monochrome or color displays, and what percentage has each type of video adapter so that you can create pictures that will look good on the end-user’s machine.
Because Windows Help is device independent, it stores text and graphics by point size rather than by their width and height in pixels. When displaying bitmaps, Windows Help tries to maintain a bitmap’s logical size across all displays (EGA, VGA, or 8514, for example). When displaying bitmaps, Help sizes text and graphics proportionately by preserving the authored point size of the text or bitmap file. Because screens have different point sizes based on their resolution, bitmaps take up different proportions of the screen. This means that a picture will distort unless the author’s display and the user’s display have the same resolution.
Therefore, to make certain that the pictures you create display correctly on the user’s display, you should create pictures in the same screen resolution (EGA, VGA, VGA+, or 8514) that you want Windows Help to use when it displays the topics on the user’s computer. For example, if most of your users have VGA adapters, you should create the pictures on a machine with standard VGA resolution. (For more information about supporting multiple display resolutions in Help, see Chapter 12, “Creating Graphics for Different Displays.”)
When creating color pictures for Help files, Windows Help assumes that your pictures have 16 or fewer colors. If you don’t use Windows Paintbrush to create the pictures, the color palette in your paint program should have no more than 16 colors. Since Windows Help supports only 16-color pictures, you don’t need to worry about palette conflicts—all pictures use the standard Windows system palette. However, you may have to make palette adjustments in the graphics application, especially if the graphics program has 256-color support. If you create a monochrome bitmap using Word for Windows, the monochrome bitmap uses the window’s foreground and background colors.
The descriptions in the remaining sections of this chapter assume that you’ve identified and prepared the pictures you want to include. If you need more information about preparing pictures, see the user’s guide for the graphics application you are using.