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Add luminance condition to validate color contrast.

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Reference WCAG to calculate color contrast via luminance, add this as
one condition for similar color validate.

Bug: 184830058
Test: atest SplashscreenTests
Change-Id: I93bad2a8ff813036e71757e50f82b6d0ea7f81d5
This commit is contained in:
wilsonshih
2021-04-20 17:24:48 +08:00
committed by Wei Sheng Shih
parent 692496d964
commit 82e484b4c3
1 changed files with 21 additions and 5 deletions
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26
libs/WindowManager/Shell/src/com/android/wm/shell/startingsurface/SplashscreenContentDrawer.java
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@@ -435,6 +435,18 @@ public class SplashscreenContentDrawer {
if (a == b) {
return true;
}
final float lumA = Color.luminance(a);
final float lumB = Color.luminance(b);
final float contrastRatio = lumA > lumB
? (lumA + 0.05f) / (lumB + 0.05f) : (lumB + 0.05f) / (lumA + 0.05f);
if (DEBUG) {
Slog.d(TAG, "isRgbSimilarInHsv a: " + Integer.toHexString(a)
+ " b " + Integer.toHexString(b) + " contrast ratio: " + contrastRatio);
}
if (contrastRatio < 2) {
return true;
}
final float[] aHsv = new float[3];
final float[] bHsv = new float[3];
Color.colorToHSV(a, aHsv);
@@ -445,14 +457,18 @@ public class SplashscreenContentDrawer {
// Calculate the difference between two colors based on the HSV dimensions.
final float normalizeH = minAngle / 180f;
final double square = Math.pow(normalizeH, 2)
+ Math.pow(aHsv[1] - bHsv[1], 2)
+ Math.pow(aHsv[2] - bHsv[2], 2);
final double squareH = Math.pow(normalizeH, 2);
final double squareS = Math.pow(aHsv[1] - bHsv[1], 2);
final double squareV = Math.pow(aHsv[2] - bHsv[2], 2);
final double square = squareH + squareS + squareV;
final double mean = square / 3;
final double root = Math.sqrt(mean);
if (DEBUG) {
Slog.d(TAG, "hsvDiff " + minAngle + " a: " + Integer.toHexString(a)
+ " b " + Integer.toHexString(b) + " ah " + aHsv[0] + " bh " + bHsv[0]
Slog.d(TAG, "hsvDiff " + minAngle
+ " ah " + aHsv[0] + " bh " + bHsv[0]
+ " as " + aHsv[1] + " bs " + bHsv[1]
+ " av " + aHsv[2] + " bv " + bHsv[2]
+ " sqH " + squareH + " sqS " + squareS + " sqV " + squareV
+ " root " + root);
}
return root < 0.1;