CPAL table

Provides named color palettes used by the COLR table for multi-colored glyphs.

Scope

• Format family: Shared SFNT
• Table tag in JSON: CPAL

Specs

• https://learn.microsoft.com/en-us/typography/opentype/spec/cpal
• OpenType table registry: https://learn.microsoft.com/en-us/typography/opentype/spec/otff#font-tables

JSON Skeleton

This skeleton reflects fields currently parsed/written by Font Flux JS for this table.

{
  "tables": {
    "CPAL": {
      "version": 0,
      "numPaletteEntries": 0,
      "palettes": null,
      "paletteTypes": null,
      "paletteLabels": null,
      "paletteEntryLabels": null,
      "_checksum": 0
    }
  }
}

Top-level Fields

• version - number (0..65535) [spec type: uint16]
• numPaletteEntries - number (0..65535) [spec type: uint16] (entries per palette)
• palettes - implementation-defined
• paletteTypes - implementation-defined
• paletteLabels - implementation-defined
• paletteEntryLabels - implementation-defined

Validation Constraints

• numPaletteEntries should match the length of each palette in palettes[].
• version = 0 supports basic palette arrays only.
• version >= 1 may include paletteTypes, paletteLabels, and paletteEntryLabels.
• All color channels are uint8 BGRA values (blue, green, red, alpha).

Authoring Example

{
	"tables": {
		"CPAL": {
			"version": 0,
			"numPaletteEntries": 2,
			"palettes": [
				[
					{ "blue": 0, "green": 0, "red": 0, "alpha": 255 },
					{ "blue": 255, "green": 255, "red": 255, "alpha": 255 }
				]
			],
			"_checksum": 0
		}
	}
}

Additional Nested Keys Seen In Implementation

• blue
• green
• red
• alpha
• paletteTypes
• paletteLabels
• paletteEntryLabels

Notes

• Preserve _checksum for stable round-tripping.
• If a table is only partially understood, prefer keeping unknown bytes in _raw instead of dropping data.
• Validate with .validate() after edits.