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Add method to Style to deduce foreground color from background color.

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Antonio El Khoury 2014-08-15 13:35:10 +02:00 • committed by Andreas Schildbach
parent aee3fba9cf
commit 4b873b60f5
2 changed files with 50 additions and 0 deletions
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12
enabler/src/de/schildbach/pte/dto/Style.java
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@ -125,4 +125,16 @@ public class Style implements Serializable
{ {
return color & 0xff; return color & 0xff;
} }
public static int deriveForegroundColor(final int backgroundColor)
{
// 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;
// dark colors, white font. Or light colors, black font
if (a >= 0.5)
return WHITE;
else
return BLACK;
}
} }

38
enabler/test/de/schildbach/pte/dto/StyleTest.java
View file

@ -32,4 +32,42 @@ public class StyleTest
final int color = Style.parseColor("#123456"); final int color = Style.parseColor("#123456");
assertEquals(color, Style.rgb(Style.red(color), Style.green(color), Style.blue(color))); assertEquals(color, Style.rgb(Style.red(color), Style.green(color), Style.blue(color)));
} }
@Test
public void deriveForegroundColorForLightBackground()
{
final int acacia = Style.rgb(205, 200, 63);
final int lilac = Style.rgb(197, 163, 202);
final int mint = Style.rgb(121, 187, 146);
final int ochre = Style.rgb(223, 176, 57);
final int orange = Style.rgb(222, 139, 83);
final int ranunculus = Style.rgb(242, 201, 49);
final int rose = Style.rgb(223, 154, 177);
final int vinca = Style.rgb(137, 199, 214);
assertEquals(Style.BLACK, Style.deriveForegroundColor(acacia));
assertEquals(Style.BLACK, Style.deriveForegroundColor(lilac));
assertEquals(Style.BLACK, Style.deriveForegroundColor(mint));
assertEquals(Style.BLACK, Style.deriveForegroundColor(ochre));
assertEquals(Style.BLACK, Style.deriveForegroundColor(orange));
assertEquals(Style.BLACK, Style.deriveForegroundColor(ranunculus));
assertEquals(Style.BLACK, Style.deriveForegroundColor(rose));
assertEquals(Style.BLACK, Style.deriveForegroundColor(vinca));
}
@Test
public void deriveForegroundColorForDarkBackground()
{
final int azure = Style.rgb(33, 110, 180);
final int brown = Style.rgb(141, 101, 56);
final int iris = Style.rgb(103, 50, 142);
final int parme = Style.rgb(187, 77, 152);
final int sapin = Style.rgb(50, 142, 91);
assertEquals(Style.WHITE, Style.deriveForegroundColor(azure));
assertEquals(Style.WHITE, Style.deriveForegroundColor(brown));
assertEquals(Style.WHITE, Style.deriveForegroundColor(iris));
assertEquals(Style.WHITE, Style.deriveForegroundColor(parme));
assertEquals(Style.WHITE, Style.deriveForegroundColor(sapin));
}
} }