JAL-2068 convenience helper method for graduated score colour

diff --git a/src/jalview/util/ColorUtils.java b/src/jalview/util/ColorUtils.java
index b8cd563..042654d 100644 (file)
--- a/src/jalview/util/ColorUtils.java
+++ b/src/jalview/util/ColorUtils.java
@@ -103,4 +103,39 @@ public class ColorUtils
     return col == null ? null : col.brighter().brighter().brighter();
   }
 
+  /**
+   * Returns a color between minColour and maxColour; the RGB values are in
+   * proportion to where 'value' lies between minValue and maxValue
+   * 
+   * @param value
+   * @param minValue
+   * @param minColour
+   * @param maxValue
+   * @param maxColour
+   * @return
+   */
+  public static Color getGraduatedColour(float value, float minValue,
+          Color minColour, float maxValue, Color maxColour)
+  {
+    if (value < minValue)
+    {
+      value = minValue;
+    }
+    if (value > maxValue)
+    {
+      value = maxValue;
+    }
+
+    /*
+     * prop = proportion of the way value is from minValue to maxValue
+     */
+    float prop = (value - minValue) / (maxValue - minValue);
+    float r = minColour.getRed() + prop
+            * (maxColour.getRed() - minColour.getRed());
+    float g = minColour.getGreen() + prop
+            * (maxColour.getGreen() - minColour.getGreen());
+    float b = minColour.getBlue() + prop
+            * (maxColour.getBlue() - minColour.getBlue());
+    return new Color(r / 255, g / 255, b / 255);
+  }
 }

diff --git a/test/jalview/util/ColorUtilsTest.java b/test/jalview/util/ColorUtilsTest.java
index 2b12a72..ca1aca0 100644 (file)
--- a/test/jalview/util/ColorUtilsTest.java
+++ b/test/jalview/util/ColorUtilsTest.java
@@ -72,4 +72,58 @@ public class ColorUtilsTest
     assertEquals("#800080", ColorUtils.toTkCode(new Color(128, 0, 128))); // purple
     assertEquals("#00ff00", ColorUtils.toTkCode(new Color(0, 255, 0))); // lime
   }
+
+  @Test(groups = { "Functional" })
+  public void testGetGraduatedColour()
+  {
+    Color minColour = new Color(100, 100, 100);
+    Color maxColour = new Color(180, 200, 220);
+
+    /*
+     * value half-way between min and max
+     */
+    Color col = ColorUtils.getGraduatedColour(20f, 10f, minColour, 30f,
+            maxColour);
+    assertEquals(140, col.getRed());
+    assertEquals(150, col.getGreen());
+    assertEquals(160, col.getBlue());
+
+    /*
+     * value two-thirds of the way between min and max
+     */
+    col = ColorUtils
+            .getGraduatedColour(30f, 10f, minColour, 40f, maxColour);
+    assertEquals(153, col.getRed());
+    // Color constructor rounds float value to nearest int
+    assertEquals(167, col.getGreen());
+    assertEquals(180, col.getBlue());
+
+    /*
+     * value = min
+     */
+    col = ColorUtils
+            .getGraduatedColour(10f, 10f, minColour, 30f, maxColour);
+    assertEquals(minColour, col);
+
+    /*
+     * value = max
+     */
+    col = ColorUtils
+            .getGraduatedColour(30f, 10f, minColour, 30f, maxColour);
+    assertEquals(maxColour, col);
+
+    /*
+     * value < min
+     */
+    col = ColorUtils.getGraduatedColour(0f, 10f, minColour, 30f, maxColour);
+    assertEquals(minColour, col);
+
+    /*
+     * value > max
+     */
+    col = ColorUtils
+            .getGraduatedColour(40f, 10f, minColour, 30f,
+            maxColour);
+    assertEquals(maxColour, col);
+  }
 }