Add BitmapTransformation to rotate the image (#3444)

* Added BitmapTransformation for rotation

* Improved override methods

library/src/main/java/com/bumptech/glide/load/resource/bitmap/Rotate.java

@@ -0,0 +1,55 @@
+package com.bumptech.glide.load.resource.bitmap;
+
+import android.graphics.Bitmap;
+import android.support.annotation.NonNull;
+import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
+import com.bumptech.glide.util.Util;
+import java.nio.ByteBuffer;
+import java.security.MessageDigest;
+
+/**
+ * A {@link BitmapTransformation} which rotates the bitmap.
+ */
+public class Rotate extends BitmapTransformation {
+  private static final String ID = "com.bumptech.glide.load.resource.bitmap.Rotate";
+  private static final byte[] ID_BYTES = ID.getBytes(CHARSET);
+
+  private final int degreesToRotate;
+
+  /**
+    * @param degreesToRotate number of degrees to rotate the image by. If zero the original image is
+    *                        not modified.
+   */
+  public Rotate(int degreesToRotate) {
+    this.degreesToRotate = degreesToRotate;
+  }
+
+  @Override
+  protected Bitmap transform(
+      @NonNull BitmapPool pool, @NonNull Bitmap toTransform, int outWidth, int outHeight) {
+    return TransformationUtils.rotateImage(toTransform, degreesToRotate);
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (o instanceof Rotate) {
+      Rotate other = (Rotate) o;
+      return degreesToRotate == other.degreesToRotate;
+    }
+    return false;
+  }
+
+  @Override
+  public int hashCode() {
+    return Util.hashCode(ID.hashCode(),
+            Util.hashCode(degreesToRotate));
+  }
+
+  @Override
+  public void updateDiskCacheKey(@NonNull MessageDigest messageDigest) {
+    messageDigest.update(ID_BYTES);
+
+    byte[] degreesData = ByteBuffer.allocate(4).putInt(degreesToRotate).array();
+    messageDigest.update(degreesData);
+  }
+}