Skip to content

⚡ Bolt: Optimize ContrastValidator relativeLuminance #132

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
mttmcknn wants to merge 1 commit into
base: main
Choose a base branch
from
Open

⚡ Bolt: Optimize ContrastValidator relativeLuminance #132

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
19 changes: 9 additions & 10 deletions halogen-core/src/commonMain/kotlin/halogen/ContrastValidator.kt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -88,16 +88,14 @@ internal object ContrastValidator {
/**
* Compute the relative luminance of an ARGB color.
*
* Uses the sRGB linearization formula per WCAG 2.1:
* - Normalize each channel to 0.0-1.0.
* - Linearize: if value <= 0.04045, divide by 12.92;
* otherwise, ((value + 0.055) / 1.055) ^ 2.4.
* - L = 0.2126 * R + 0.7152 * G + 0.0722 * B.
* Uses a pre-computed lookup table for the sRGB linearization formula
* to significantly improve performance in this hot path by avoiding
* repetitive division and Math.pow() calculations.
*/
fun relativeLuminance(argb: Int): Double {
val r = linearize(((argb shr 16) and 0xFF) / 255.0)
val g = linearize(((argb shr 8) and 0xFF) / 255.0)
val b = linearize((argb and 0xFF) / 255.0)
val r = LINEARIZE_LUT[(argb shr 16) and 0xFF]
val g = LINEARIZE_LUT[(argb shr 8) and 0xFF]
val b = LINEARIZE_LUT[argb and 0xFF]
return 0.2126 * r + 0.7152 * g + 0.0722 * b
}

Expand All @@ -120,8 +118,9 @@ internal object ContrastValidator {
return contrastRatio(foreground, background) >= AA_RATIO
}

private fun linearize(component: Double): Double {
return if (component <= 0.04045) {
private val LINEARIZE_LUT: DoubleArray = DoubleArray(256) { i ->
val component = i / 255.0
if (component <= 0.04045) {
component / 12.92
} else {
((component + 0.055) / 1.055).pow(2.4)
Expand Down
Loading