diff --git a/transformations/src/main/java/jp/wasabeef/glide/transformations/gpu/ContrastFilterTransformation.java b/transformations/src/main/java/jp/wasabeef/glide/transformations/gpu/ContrastFilterTransformation.java
index ec7cd67..ec02e1b 100644
--- a/transformations/src/main/java/jp/wasabeef/glide/transformations/gpu/ContrastFilterTransformation.java
+++ b/transformations/src/main/java/jp/wasabeef/glide/transformations/gpu/ContrastFilterTransformation.java
@@ -27,6 +27,9 @@ import android.graphics.Bitmap;
 import jp.co.cyberagent.android.gpuimage.GPUImage;
 import jp.co.cyberagent.android.gpuimage.GPUImageContrastFilter;
 
+/**
+ * contrast value ranges from 0.0 to 4.0, with 1.0 as the normal level
+ */
 public class ContrastFilterTransformation implements Transformation<Bitmap> {
 
     private Context mContext;
diff --git a/transformations/src/main/java/jp/wasabeef/glide/transformations/gpu/SwirlFilterTransformation.java b/transformations/src/main/java/jp/wasabeef/glide/transformations/gpu/SwirlFilterTransformation.java
index 3e83c3b..cc298f9 100644
--- a/transformations/src/main/java/jp/wasabeef/glide/transformations/gpu/SwirlFilterTransformation.java
+++ b/transformations/src/main/java/jp/wasabeef/glide/transformations/gpu/SwirlFilterTransformation.java
@@ -42,6 +42,11 @@ public class SwirlFilterTransformation implements Transformation<Bitmap> {
         mBitmapPool = pool;
     }
 
+    /**
+     * @param radius from 0.0 to 1.0, default 0.5
+     * @param angle  minimum 0.0, default 1.0
+     * @param center default (0.5, 0.5)
+     */
     public SwirlFilterTransformation(Context context, BitmapPool pool,
             float radius, float angle, PointF center) {
         mContext = context;