Apply a gaussian blur filter, and return a new (blurred) bitmap that's the same size as the input bitmap. - Android Graphics

Android examples for Graphics:Bitmap Blur

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Description

Apply a gaussian blur filter, and return a new (blurred) bitmap that's the same size as the input bitmap.

Demo Code

/*//from w w  w  .j  a  va  2  s.  c o m
 * 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.
 */
import android.graphics.Bitmap;
import android.os.SystemClock;
import android.util.Log;

public class Main{
    private static final String TAG = "BitmapUtils";
    private static boolean DBG = true;
    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;
    /**
     * 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 log(String msg) {
        Logger.d(TAG, msg);
    }
    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;
        }
    }
}

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