`TCustomPngNonInterlacedEncoder`
pt		ColorInPalette
pt		TransferData
		Create
		Destroy
		EncodeFromScanline

`TCustomPngEncoder`
pt		FilterSub
pt		FilterUp
pt		FilterAverage
pt		FilterPaeth
pt		EncodeFilterRow
		EncodeFromScanline

`TCustomPngCoder`
pt		BuildMappingTable
		Create
		Destroy