CBLC — Color Bitmap Location Table (OpenType 1.8.1)

Table structure

The 'CBLC' table provides embedded bitmap locators. It is used together with the 'CBDT' table, which provides embedded, color bitmap glyph data. The formats of these two tables are backward compatible with the 'EBDT' and 'EBLC' tables used for embedded monochrome and grayscale bitmaps.

The 'CBLC' table begins with a header containing the table version and number of strikes.

cblcHeader

Type	Name	Description
uint16	majorVersion	Major version of the 'CBLC' table, = 3.
uint16	minorVersion	Minor version of the 'CBLC' table, = 0.
uint32	numsizes	Number of bitmapSizeTables

Note that the first version of the 'CBLC' table is 3.0.

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
Offset32	indexSubTableArrayOffset	Offset to index subtable from beginning of 'CBLC'.
uint32	indexTablesSize	number of bytes in corresponding index subtables and array
uint32	numberofIndexSubTables	an index subtable for each range or format change
uint32	colorRef	not used; set to 0.
sbitLineMetrics	Hori	line metrics for text rendered horizontally
sbitLineMetrics	Vert	line metrics for text rendered vertically
uint16	startGlyphIndex	lowest glyph index for this size
uint16	endGlyphIndex	highest glyph index for this size
uint8	ppemX	horizontal pixels per Em
uint8	ppemY	vertical pixels per Em
uint8	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
int8	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'.