wip: add more constants

nrkno · Aug 15, 2024 · 2384a87 · 2384a87
1 parent ebfd65c
commit 2384a87
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Showing 2 changed files with 10 additions and 5 deletions.
diff --git a/src/lib/converters/colorConstants.ts b/src/lib/converters/colorConstants.ts
@@ -13,17 +13,20 @@ export interface ColorConvertConstants {
 	readonly YOffset: number
 	readonly CbCrOffset: number
 
+	readonly KRKRioKG: number
+	readonly KBKBioKG: number
+
 	readonly KRoKBi: number
 	readonly KGoKBi: number
 	readonly KBoKRi: number
 	readonly KGoKRi: number
 }
 
 function createColorConvertConstants(KR: number, KB: number): ColorConvertConstants {
-	const KG = 1 - KR - KB
+	const KG = 1 - KR - KB // 0.7152
 
-	const KRi = 1 - KR
-	const KBi = 1 - KB
+	const KRi = 1 - KR // 0.7874 -> 1.5748
+	const KBi = 1 - KB // 0.9278 -> 1.8556
 
 	const YRange = 219
 	const CbCrRange = 224
@@ -44,6 +47,9 @@ function createColorConvertConstants(KR: number, KB: number): ColorConvertConsta
 		YOffset: 16 << 8,
 		CbCrOffset: 128 << 8,
 
+		KRKRioKG: (KR * KRi * 2) / KG,
+		KBKBioKG: (KB * KBi * 2) / KG,
+
 		KRoKBi: (KR / KBi) * HalfCbCrRange,
 		KGoKBi: (KG / KBi) * HalfCbCrRange,
 		KBoKRi: (KB / KRi) * HalfCbCrRange,

diff --git a/src/lib/converters/yuv422ToRgba.ts b/src/lib/converters/yuv422ToRgba.ts
@@ -33,8 +33,7 @@ export function convertYUV422ToRGBA(width: number, height: number, data: Buffer)
 		a10: number
 	): [r: number, g: number, b: number, a: number] => {
 		const r = clamp(Math.round(y8 + constants.KRi * cr8))
-		// TODO - use more constants
-		const g = clamp(Math.round(y8 - ((0.2126 * 1.5748) / 0.7152) * cr8 - ((0.0722 * 1.8556) / 0.7152) * cb8))
+		const g = clamp(Math.round(y8 - constants.KRKRioKG * cr8 - constants.KBKBioKG * cb8))
 		const b = clamp(Math.round(y8 + constants.KBi * cb8))
 		const a = Math.round(a10)