EBDT: Bitmap Data
The 'EBDT' table stores glyph bitmap data, in a number of possible format. It works together with the 'EBLC' table, which identifies the sizes and glyph ranges of the bitmaps, and keeps offsets to the bitmap data in 'EBDT'.
Requirements
- Embed bitmaps in TrueType fonts, instead of shipping WIFE or .FON files. WIFE is not installed by default for Windows 95, and you should not assume that WIFE will be supported on future platforms.
Recommendations
- Fonts should include bigMetrics data in the 'EBDT' or 'EBLC' table, to support both vertical and horizontal writing. However, if the 'EBDT'/'EBLC' tables contain vertical metrics for bitmaps, the font must also include 'vhea' and 'vmtx' tables to provide vertical metrics for outlines.
- 'EBDT' format 5 (metrics in 'EBLC', bit-aligned image data only) is recommended for Far East fonts, where typically every glyph has the same metrics. But in order to count as "shared metrics", the bitmap images may need to be padded with white pixels, which distorts GDI's information about ABC widths. To compensate for this, the TrueType rasterizer recalculates ABC widths on the fly for bitmaps stored in 'EBDT' format 5 only. This allows use of the space-saving constant metrics format, without unnecessarily confusing application clients.
- Format 9 (big metrics, component data) may be appropriate for Korean fonts.