add color filter documentation to README (#219)
diff --git a/README.md b/README.md
index 176a35c..291b345 100644
--- a/README.md
+++ b/README.md
@@ -121,6 +121,24 @@
animationView.cancelAnimation();
```
+You can add a color filter to the whole animation, a specific layer, or specific content within a layer:
+```java
+// Any class that conforms to the ColorFilter interface
+final SimpleColorFilter colorFilter = new SimpleColorFilter(Color.RED);
+
+// Adding a color filter to the whole view
+animationView.addColorFilter(colorFilter);
+
+// Adding a color filter to a specific layer
+animationView.addColorFilterToLayer("hello_layer", colorFilter);
+
+// Adding a color filter to specfic content on the "hello_layer"
+animationView.addColorFilterToContent("hello_layer", "hello", colorFilter);
+
+// Clear all color filters
+animationView.clearColorFilters();
+```
+Note: Color filters are only available for layers such as Image layer and Solid layer as well as content that includes fill, stroke, or group content.
Under the hood, `LottieAnimationView` uses `LottieDrawable` to render its animations. If you need to, you can use the drawable form directly:
```java
diff --git a/lottie/src/main/java/com/airbnb/lottie/SimpleColorFilter.java b/lottie/src/main/java/com/airbnb/lottie/SimpleColorFilter.java
new file mode 100644
index 0000000..410969c
--- /dev/null
+++ b/lottie/src/main/java/com/airbnb/lottie/SimpleColorFilter.java
@@ -0,0 +1,19 @@
+package com.airbnb.lottie;
+
+import android.graphics.PorterDuff;
+import android.graphics.PorterDuffColorFilter;
+import android.support.annotation.ColorInt;
+
+/**
+ * A color filter with a predefined transfer mode that applies the specified color on top of the
+ * original color. As there are many other transfer modes, please take a look at the definition
+ * of PorterDuff.Mode.SRC_ATOP to find one that suits your needs.
+ * This site has a great explanation of Porter/Duff compositing algebra as well as a visual
+ * representation of many of the transfer modes:
+ * http://ssp.impulsetrain.com/porterduff.html
+ */
+public class SimpleColorFilter extends PorterDuffColorFilter {
+ public SimpleColorFilter(@ColorInt int color) {
+ super(color, PorterDuff.Mode.SRC_ATOP);
+ }
+}
