CBLC - Color Bitmap Location Table (OpenType 1.8)

Table structure

Two new tables are used to embed color bitmaps in OFF fonts. They are the 'CBLC' table, backward compatible with the existing EBLC table for embedded bitmap locators, and the 'CBDT' table for embedded color bitmap data.

The 'CBLC' table begins with a header containing the table version and number of strikes. An OFF font may have one or more strikes embedded in the 'CBDT' table.

cblcHeader

Type	Name	Description
FIXED	version	Initially defined as 0x00030000
ULONG	numsizes	Number of bitmapSizeTables

The cblcHeader is followed immediately by the bitmapSizeTable array(s). The numSizes in the cblcHeader indicates the number of bitmapSizeTables in the array. Each strike is defined by one bitmapSizeTable.

bitmapSizeTable

Type	Name	Description
ULONG	indexSubTableArrayOffset	Offset to index subtable from beginning of CBLC.
ULONG	indexTablesSize	number of bytes in corresponding index subtables and array
ULONG	numberofIndexSubTables	an index subtable for each range or format change
ULONG	colorRef	not used; set to 0.
sbitLineMetrics	Hori	line metrics for text rendered horizontally
sbitLineMetrics	Vert	line metrics for text rendered vertically
USHORT	startGlyphIndex	lowest glyph index for this size
USHORT	endGlyphIndex	highest glyph index for this size
BYTE	ppemX	horizontal pixels per Em
BYTE	ppemY	vertical pixels per Em
BYTE	bitDepth	In addtition to already defined bitDepth values 1, 2, 4, and 8 supported by existing implementations, the value of 32 is used to identify color bitmaps with 8 bit per pixel RGBA channels
CHAR	Flags	vertical or horizontal (see bitmapFlags)

The indexSubTableArrayOffset is the offset from the beginning of the 'CBLC' table to the indexSubTableArray. Each strike has one of these arrays to support various formats and discontiguous ranges of bitmaps. The indexTablesSize is the total number of bytes in the indexSubTableArray and the associated indexSubTables. The numberOfIndexSubTables is a count of the indexSubTables for this strike.

The rest of the CBLC table structure is identical to one already defined for EBLC