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Add method to determine the perceived brightness of a color.

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This commit is contained in:
Andreas Schildbach 2015-02-23 11:54:01 +01:00
parent c6861282f3
commit eb1092c9f8
1 changed files with 6 additions and 3 deletions
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9
enabler/src/de/schildbach/pte/dto/Style.java
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@ -128,13 +128,16 @@ public class Style implements Serializable
return color & 0xff;
}
public static int deriveForegroundColor(final int backgroundColor)
public static float perceivedBrightness(final int color)
{
// formula for perceived brightness computation: http://www.w3.org/TR/AERT#color-contrast
final double a = 1 - (0.299 * Style.red(backgroundColor) + 0.587 * Style.green(backgroundColor) + 0.114 * Style.blue(backgroundColor)) / 255;
return (0.299f * Style.red(color) + 0.587f * Style.green(color) + 0.114f * Style.blue(color)) / 256;
}
public static int deriveForegroundColor(final int backgroundColor)
{
// dark colors, white font. Or light colors, black font
if (a >= 0.5)
if (perceivedBrightness(backgroundColor) < 0.5)
return WHITE;
else
return BLACK;