31.1.2 Graphics formats for WinHelp
WinHelp graphics must be in WMF or BMP format. Graphics are viewed at screen resolution, typically 96 DPI. Normally you want to use WMF, because WMF graphics have a much sharper image than BMP graphics. However, the WMF format has some drawbacks; see §31.1.3 WMF format limitations.
For very large graphics, BMP can be a better choice; see §31.2.1.1.3 Specifying BMP instead of WMF graphics.
WinHelp 4 allows 256-color bitmaps; the added space for 256 colors is relatively small, and the graphics usually look better than with 16 colors. WinHelp 3 allows only 16-color bitmaps (unless you use add-on DLLs). For any WinHelp use, 24-bit color (“true color”) is a very bad idea; it often crashes the Help Compiler during processing.
