Add color interpolation helper.

litiengine/src/main/java/de/gurkenlabs/litiengine/util/ColorHelper.java

@@ -5,6 +5,7 @@
 import java.util.logging.Logger;
 
 public final class ColorHelper {
+
  private static final Logger log = Logger.getLogger(ColorHelper.class.getName());
  private static final int HEX_STRING_LENGTH = 7;
  private static final int HEX_STRING_LENGTH_ALPHA = 9;
@@ -21,13 +22,12 @@ private ColorHelper() {
  * <li>#RRGGBB - For colors without alpha
  * <li>#AARRGGBB - For colors with alpha
  * </ul>
- *
+ * <p>
  * Examples: <br>
  * {@code Color.RED} = "#ff0000"<br>
  * {@code new Color(255, 0, 0, 200)} = "#c8ff0000"
  *
- * @param color
- * The color that is encoded.
+ * @param color The color that is encoded.
  * @return An hexadecimal string representation of the specified color.
  * @see ColorHelper#decode(String)
  * @see Color
@@ -48,7 +48,8 @@ public static String encode(Color color) {
  }
 
  /**
- * Decodes the specified color string to an actual {@code Color} instance. The accepted format is:
+ * Decodes the specified color string to an actual {@code Color} instance. The accepted format
+ * is:
  * <p>
  * <i>Note: This returns null if the format of the provided color string is invalid.</i>
  * </p>
@@ -57,13 +58,12 @@ public static String encode(Color color) {
  * <li>#RRGGBB - For colors without alpha
  * <li>#AARRGGBB - For colors with alpha
  * </ul>
- *
+ * <p>
  * Examples: <br>
  * "#ff0000" = {@code Color.RED}<br>
  * "#c8ff0000" = {@code new Color(255, 0, 0, 200)}
  *
- * @param colorHexString
- * The hexadecimal encodes color string representation.
+ * @param colorHexString The hexadecimal encodes color string representation.
  * @return The decoded color.
  * @see ColorHelper#encode(Color)
  * @see Color
@@ -81,13 +81,13 @@ public static Color decode(String colorHexString, boolean solid) {
 
  if (!colorHexString.startsWith("#")) {
  if (colorHexString.length() == HEX_STRING_LENGTH - 1
-  || colorHexString.length() == HEX_STRING_LENGTH_ALPHA - 1) {
+ || colorHexString.length() == HEX_STRING_LENGTH_ALPHA - 1) {
  colorHexString = "#" + colorHexString;
  } else {
  log.log(
-  Level.SEVERE,
-  "Could not parse color string \"{0}\". A color string needs to start with a \"#\" character.",
-  colorHexString);
+ Level.SEVERE,
+ "Could not parse color string \"{0}\". A color string needs to start with a \"#\" character.",
+ colorHexString);
  return null;
  }
  }
@@ -99,33 +99,31 @@ public static Color decode(String colorHexString, boolean solid) {
  return decodeHexStringWithAlpha(colorHexString, solid);
  default:
  log.log(
-  Level.SEVERE,
-  "Could not parse color string \"{0}\". Invalid string length \"{1}\"!\nAccepted lengths:\n\t{2} for Colors without Alpha (#ff0000)\n\t{3} for Colors with Alpha (#c8ff0000)",
-  new Object[] {
-  colorHexString, colorHexString.length(), HEX_STRING_LENGTH, HEX_STRING_LENGTH_ALPHA
-  });
+ Level.SEVERE,
+ "Could not parse color string \"{0}\". Invalid string length \"{1}\"!\nAccepted lengths:\n\t{2} for Colors without Alpha (#ff0000)\n\t{3} for Colors with Alpha (#c8ff0000)",
+ new Object[]{
+ colorHexString, colorHexString.length(), HEX_STRING_LENGTH, HEX_STRING_LENGTH_ALPHA
+ });
  return null;
  }
  }
 
  /**
- * Ensures that the specified value lies within the accepted range for Color values (0-255). Smaller values will be
- * forced to be 0 and larger values will result in 255.
+ * Ensures that the specified value lies within the accepted range for Color values (0-255).
+ * Smaller values will be forced to be 0 and larger values will result in 255.
  *
- * @param value
- * The value to check for.
+ * @param value The value to check for.
  * @return An integer value that fits the color value restrictions.
  */
  public static int ensureColorValueRange(float value) {
  return ensureColorValueRange(Math.round(value));
  }
 
  /**
- * Ensures that the specified value lies within the accepted range for Color values (0-255). Smaller values will be
- * forced to be 0 and larger values will result in 255.
+ * Ensures that the specified value lies within the accepted range for Color values (0-255).
+ * Smaller values will be forced to be 0 and larger values will result in 255.
  *
- * @param value
- * The value to check for.
+ * @param value The value to check for.
  * @return An integer value that fits the color value restrictions.
  */
  public static int ensureColorValueRange(int value) {
@@ -135,23 +133,33 @@ public static int ensureColorValueRange(int value) {
  /**
  * Premultiplies the alpha on the given color.
  *
- * @param color
- * The color to premultiply
+ * @param color The color to premultiply
  * @return The color given, with alpha replaced with a black background.
  */
  public static Color premultiply(Color color) {
  if (color.getAlpha() == 255) {
  return color;
  }
  return new Color(
- premultiply(color.getRed(), color.getAlpha()),
- premultiply(color.getGreen(), color.getAlpha()),
- premultiply(color.getBlue(), color.getAlpha()));
+ premultiply(color.getRed(), color.getAlpha()),
+ premultiply(color.getGreen(), color.getAlpha()),
+ premultiply(color.getBlue(), color.getAlpha()));
+ }
+
+ public static Color interpolate(Color color1, Color color2, double factor) {
+ factor = MathUtilities.clamp(factor, 0, 1);
+
+ int r = (int) (color1.getRed() * (1 - factor) + color2.getRed() * factor);
+ int g = (int) (color1.getGreen() * (1 - factor) + color2.getGreen() * factor);
+ int b = (int) (color1.getBlue() * (1 - factor) + color2.getBlue() * factor);
+ int a = (int) (color1.getAlpha() * (1 - factor) + color2.getAlpha() * factor);
+
+ return new Color(r, g, b, a);
  }
 
  public static Color getTransparentVariant(Color color, int newAlpha) {
  return new Color(
-  color.getRed(), color.getGreen(), color.getBlue(), ensureColorValueRange(newAlpha));
+ color.getRed(), color.getGreen(), color.getBlue(), ensureColorValueRange(newAlpha));
  }
 
  private static Color decodeWellformedHexString(String hexString) {