Adding support for dynamically adding shadows to the icon

Change-Id: I94d98750aea1faef8879e25990aa5c41a4894708

src/com/android/launcher3/graphics/ShadowGenerator.java

@@ -0,0 +1,114 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.launcher3.graphics;
+
+import android.graphics.Bitmap;
+import android.graphics.Bitmap.Config;
+import android.graphics.BlurMaskFilter;
+import android.graphics.BlurMaskFilter.Blur;
+import android.graphics.Canvas;
+import android.graphics.Paint;
+import android.graphics.RectF;
+
+import com.android.launcher3.LauncherAppState;
+import com.android.launcher3.util.Preconditions;
+
+/**
+ * Utility class to add shadows to bitmaps.
+ */
+public class ShadowGenerator {
+
+    // Percent of actual icon size
+    private static final float HALF_DISTANCE = 0.5f;
+    private static final float BLUR_FACTOR = 0.5f/48;
+
+    // Percent of actual icon size
+    private static final float KEY_SHADOW_DISTANCE = 1f/48;
+    private static final int KEY_SHADOW_ALPHA = 61;
+
+    private static final int AMBIENT_SHADOW_ALPHA = 30;
+
+    private static final Object LOCK = new Object();
+    // Singleton object guarded by {@link #LOCK}
+    private static ShadowGenerator sShadowGenerator;
+
+    private final int mIconSize;
+
+    private final Canvas mCanvas;
+    private final Paint mBlurPaint;
+    private final Paint mDrawPaint;
+
+    private ShadowGenerator() {
+        mIconSize = LauncherAppState.getInstance().getInvariantDeviceProfile().iconBitmapSize;
+        mCanvas = new Canvas();
+        mBlurPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.FILTER_BITMAP_FLAG);
+        mBlurPaint.setMaskFilter(new BlurMaskFilter(mIconSize * BLUR_FACTOR, Blur.NORMAL));
+        mDrawPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.FILTER_BITMAP_FLAG);
+    }
+
+    public synchronized Bitmap recreateIcon(Bitmap icon) {
+        int[] offset = new int[2];
+        Bitmap shadow = icon.extractAlpha(mBlurPaint, offset);
+        Bitmap result = Bitmap.createBitmap(mIconSize, mIconSize, Config.ARGB_8888);
+        mCanvas.setBitmap(result);
+
+        // Draw ambient shadow
+        mDrawPaint.setAlpha(AMBIENT_SHADOW_ALPHA);
+        mCanvas.drawBitmap(shadow, offset[0], offset[1], mDrawPaint);
+
+        // Draw key shadow
+        mDrawPaint.setAlpha(KEY_SHADOW_ALPHA);
+        mCanvas.drawBitmap(shadow, offset[0], offset[1] + KEY_SHADOW_DISTANCE * mIconSize, mDrawPaint);
+
+        // Draw the icon
+        mDrawPaint.setAlpha(255);
+        mCanvas.drawBitmap(icon, 0, 0, mDrawPaint);
+
+        mCanvas.setBitmap(null);
+        return result;
+    }
+
+    public static ShadowGenerator getInstance() {
+        Preconditions.assertNonUiThread();
+        synchronized (LOCK) {
+            if (sShadowGenerator == null) {
+                sShadowGenerator = new ShadowGenerator();
+            }
+        }
+        return sShadowGenerator;
+    }
+
+    /**
+     * Returns the minimum amount by which an icon with {@param bounds} should be scaled
+     * so that the shadows do not get clipped.
+     */
+    public static float getScaleForBounds(RectF bounds) {
+        float scale = 1;
+
+        // For top, left & right, we need same space.
+        float minSide = Math.min(Math.min(bounds.left, bounds.right), bounds.top);
+        if (minSide < BLUR_FACTOR) {
+            scale = (HALF_DISTANCE - BLUR_FACTOR) / (HALF_DISTANCE - minSide);
+        }
+
+        float bottomSpace = BLUR_FACTOR + KEY_SHADOW_DISTANCE;
+        if (bounds.bottom < bottomSpace) {
+            scale = Math.min(scale, (HALF_DISTANCE - bottomSpace) / (HALF_DISTANCE - bounds.bottom));
+        }
+        return scale;
+    }
+}