src/com/android/phone/BitmapUtils.java

/*
 * Copyright (C) 2011 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.phone;

import android.graphics.Bitmap;
import android.os.SystemClock;
import android.os.SystemProperties;
import android.util.Log;


/**
 * Image effects used by the in-call UI.
 */
public class BitmapUtils {
    private static final String TAG = "BitmapUtils";
    private static final boolean DBG =
            (PhoneGlobals.DBG_LEVEL >= 1) && (SystemProperties.getInt("ro.debuggable", 0) == 1);

    /** This class is never instantiated. */
    private BitmapUtils() {
    }

    //
    // Gaussian blur effect
    //
    // gaussianBlur() and related methods are borrowed from
    // BackgroundUtils.java in the Music2 code (which itself was based on
    // code from the old Cooliris android Gallery app.)
    //
    // TODO: possibly consider caching previously-generated blurred bitmaps;
    // see getAdaptedBitmap() and mAdaptedBitmapCache in the music app code.
    //

    private static final int RED_MASK = 0xff0000;
    private static final int RED_MASK_SHIFT = 16;
    private static final int GREEN_MASK = 0x00ff00;
    private static final int GREEN_MASK_SHIFT = 8;
    private static final int BLUE_MASK = 0x0000ff;

    /**
     * Creates a blurred version of the given Bitmap.
     *
     * @param bitmap the input bitmap, presumably a 96x96 pixel contact
     *               thumbnail.
     */
    public static Bitmap createBlurredBitmap(Bitmap bitmap) {
        if (DBG) log("createBlurredBitmap()...");
        long startTime = SystemClock.uptimeMillis();
        if (bitmap == null) {
            Log.w(TAG, "createBlurredBitmap: null bitmap");
            return null;
        }

        if (DBG) log("- input bitmap: " + bitmap.getWidth() + " x " + bitmap.getHeight());

        // The bitmap we pass to gaussianBlur() needs to have a width
        // that's a power of 2, so scale up to 128x128.
        final int scaledSize = 128;
        bitmap = Bitmap.createScaledBitmap(bitmap,
                                           scaledSize, scaledSize,
                                           true /* filter */);
        if (DBG) log("- after resize: " + bitmap.getWidth() + " x " + bitmap.getHeight());

        bitmap = gaussianBlur(bitmap);
        if (DBG) log("- after blur: " + bitmap.getWidth() + " x " + bitmap.getHeight());

        long endTime = SystemClock.uptimeMillis();
        if (DBG) log("createBlurredBitmap() done (elapsed = " + (endTime - startTime) + " msec)");
        return bitmap;
    }

    /**
     * Apply a gaussian blur filter, and return a new (blurred) bitmap
     * that's the same size as the input bitmap.
     *
     * @param source input bitmap, whose width must be a power of 2
     */
    public static Bitmap gaussianBlur(Bitmap source) {
        int width = source.getWidth();
        int height = source.getHeight();
        if (DBG) log("gaussianBlur(): input: " + width + " x " + height);

        // Create a source and destination buffer for the image.
        int numPixels = width * height;
        int[] in = new int[numPixels];
        int[] tmp = new int[numPixels];

        // Get the source pixels as 32-bit ARGB.
        source.getPixels(in, 0, width, 0, 0, width, height);

        // Gaussian is a separable kernel, so it is decomposed into a horizontal
        // and vertical pass.
        // The filter function applies the kernel across each row and transposes
        // the output.
        // Hence we apply it twice to provide efficient horizontal and vertical
        // convolution.
        // The filter discards the alpha channel.
        gaussianBlurFilter(in, tmp, width, height);
        gaussianBlurFilter(tmp, in, width, height);

        // Return a bitmap scaled to the desired size.
        Bitmap filtered = Bitmap.createBitmap(in, width, height, Bitmap.Config.ARGB_8888);
        source.recycle();
        return filtered;
    }

    private static void gaussianBlurFilter(int[] in, int[] out, int width, int height) {
        // This function is currently hardcoded to blur with RADIUS = 4.
        // (If you change RADIUS, you'll have to change the weights[] too.)
        final int RADIUS = 4;
        final int[] weights = { 13, 23, 32, 39, 42, 39, 32, 23, 13}; // Adds up to 256
        int inPos = 0;
        int widthMask = width - 1; // width must be a power of two.
        for (int y = 0; y < height; ++y) {
            // Compute the alpha value.
            int alpha = 0xff;
            // Compute output values for the row.
            int outPos = y;
            for (int x = 0; x < width; ++x) {
                int red = 0;
                int green = 0;
                int blue = 0;
                for (int i = -RADIUS; i <= RADIUS; ++i) {
                    int argb = in[inPos + (widthMask & (x + i))];
                    int weight = weights[i+RADIUS];
                    red += weight *((argb & RED_MASK) >> RED_MASK_SHIFT);
                    green += weight *((argb & GREEN_MASK) >> GREEN_MASK_SHIFT);
                    blue += weight *(argb & BLUE_MASK);
                }
                // Output the current pixel.
                out[outPos] = (alpha << 24) | ((red >> 8) << RED_MASK_SHIFT)
                    | ((green >> 8) << GREEN_MASK_SHIFT)
                        | (blue >> 8);
                outPos += height;
            }
            inPos += width;
        }
    }

    //
    // Debugging
    //

    private static void log(String msg) {
        Log.d(TAG, msg);
    }
}