[opentype] initial CPAL support

Author: benoitkugler

font/opentype/tables/glyphs_cpal_gen.go

@@ -0,0 +1,43 @@
+package tables
+
+import "fmt"
+
+func ParseCPAL(src []byte) (CPAL1, error) {
+	header, _, err := parseCpal0(src)
+	if err != nil {
+		return CPAL1{}, err
+	}
+	switch header.Version {
+	case 0:
+		return CPAL1{cpal0: header}, nil
+	case 1:
+		out, _, err := ParseCPAL1(src)
+		return out, err
+	default:
+		return CPAL1{}, fmt.Errorf("unsupported version for CPAL: %d", header.Version)
+	}
+}
+
+// https://learn.microsoft.com/en-us/typography/opentype/spec/cpal
+type cpal0 struct {
+	Version            uint16        //	Table version number
+	numPaletteEntries  uint16        //	Number of palette entries in each palette.
+	numPalettes        uint16        //	Number of palettes in the table.
+	numColorRecords    uint16        //	Total number of color records, combined for all palettes.
+	ColorRecordsArray  []ColorRecord `arrayCount:"ComputedField-numColorRecords" offsetSize:"Offset32"` //	Offset from the beginning of CPAL table to the first ColorRecord.
+	ColorRecordIndices []uint16      `arrayCount:"ComputedField-numPalettes"`                           //[numPalettes]	Index of each palette’s first color record in the combined color record array.
+}
+
+type CPAL1 struct {
+	cpal0
+	paletteTypesArrayOffset       Offset32 // Offset from the beginning of CPAL table to the Palette Types Array. Set to 0 if no array is provided.
+	paletteLabelsArrayOffset      Offset32 // Offset from the beginning of CPAL table to the Palette Labels Array. Set to 0 if no array is provided.
+	paletteEntryLabelsArrayOffset Offset32 // Offset from the beginning of CPAL table to the Palette Entry Labels Array. Set to 0 if no array is provided.
+}
+
+type ColorRecord struct {
+	Blue  uint8 // Blue value (B0).
+	Green uint8 // Green value (B1).
+	Red   uint8 // Red value (B2).
+	Alpha uint8 // Alpha value (B3).
+}