Blur

自從iOS系統引入了Blur效果，也就是所謂的毛玻璃、模糊化效果，磨砂效果，各大系統就開始競相模仿，這是一個怎樣的效果呢，我們現來看一些圖：

這些就是典型的Blur效果，在iOS和MIUI中還有很多，這裡就不再貼圖了。

<喎?/kf/ware/vc/" target="_blank" class="keylink">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"/uploadfile/2014/1009/20141009110156957.jpg" alt="\" />

有興趣的朋友可以去看看。

使用

下面我們來看看如何在Android中來使用Blur，當然，我們需要使用上面提到的FastBlur

package com.xys.blur;

import android.graphics.Bitmap;

/**
 * Created by paveld on 3/6/14.
 */
public class FastBlur {

    public static Bitmap doBlur(Bitmap sentBitmap, int radius, boolean canReuseInBitmap) {

        // Stack Blur v1.0 from
        // http://www.quasimondo.com/StackBlurForCanvas/StackBlurDemo.html
        //
        // Java Author: Mario Klingemann 
        // http://incubator.quasimondo.com
        // created Feburary 29, 2004
        // Android port : Yahel Bouaziz 
        // http://www.kayenko.com
        // ported april 5th, 2012

        // This is a compromise between Gaussian Blur and Box blur
        // It creates much better looking blurs than Box Blur, but is
        // 7x faster than my Gaussian Blur implementation.
        //
        // I called it Stack Blur because this describes best how this
        // filter works internally: it creates a kind of moving stack
        // of colors whilst scanning through the image. Thereby it
        // just has to add one new block of color to the right side
        // of the stack and remove the leftmost color. The remaining
        // colors on the topmost layer of the stack are either added on
        // or reduced by one, depending on if they are on the right or
        // on the left side of the stack.
        //
        // If you are using this algorithm in your code please add
        // the following line:
        //
        // Stack Blur Algorithm by Mario Klingemann 

        Bitmap bitmap;
        if (canReuseInBitmap) {
            bitmap = sentBitmap;
        } else {
            bitmap = sentBitmap.copy(sentBitmap.getConfig(), true);
        }

        if (radius < 1) {
            return (null);
        }

        int w = bitmap.getWidth();
        int h = bitmap.getHeight();

        int[] pix = new int[w * h];
        bitmap.getPixels(pix, 0, w, 0, 0, w, h);

        int wm = w - 1;
        int hm = h - 1;
        int wh = w * h;
        int div = radius + radius + 1;

        int r[] = new int[wh];
        int g[] = new int[wh];
        int b[] = new int[wh];
        int rsum, gsum, bsum, x, y, i, p, yp, yi, yw;
        int vmin[] = new int[Math.max(w, h)];

        int divsum = (div + 1) >> 1;
        divsum *= divsum;
        int dv[] = new int[256 * divsum];
        for (i = 0; i < 256 * divsum; i++) {
            dv[i] = (i / divsum);
        }

        yw = yi = 0;

        int[][] stack = new int[div][3];
        int stackpointer;
        int stackstart;
        int[] sir;
        int rbs;
        int r1 = radius + 1;
        int routsum, goutsum, boutsum;
        int rinsum, ginsum, binsum;

        for (y = 0; y < h; y++) {
            rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
            for (i = -radius; i <= radius; i++) {
                p = pix[yi + Math.min(wm, Math.max(i, 0))];
                sir = stack[i + radius];
                sir[0] = (p & 0xff0000) >> 16;
                sir[1] = (p & 0x00ff00) >> 8;
                sir[2] = (p & 0x0000ff);
                rbs = r1 - Math.abs(i);
                rsum += sir[0] * rbs;
                gsum += sir[1] * rbs;
                bsum += sir[2] * rbs;
                if (i > 0) {
                    rinsum += sir[0];
                    ginsum += sir[1];
                    binsum += sir[2];
                } else {
                    routsum += sir[0];
                    goutsum += sir[1];
                    boutsum += sir[2];
                }
            }
            stackpointer = radius;

            for (x = 0; x < w; x++) {

                r[yi] = dv[rsum];
                g[yi] = dv[gsum];
                b[yi] = dv[bsum];

                rsum -= routsum;
                gsum -= goutsum;
                bsum -= boutsum;

                stackstart = stackpointer - radius + div;
                sir = stack[stackstart % div];

                routsum -= sir[0];
                goutsum -= sir[1];
                boutsum -= sir[2];

                if (y == 0) {
                    vmin[x] = Math.min(x + radius + 1, wm);
                }
                p = pix[yw + vmin[x]];

                sir[0] = (p & 0xff0000) >> 16;
                sir[1] = (p & 0x00ff00) >> 8;
                sir[2] = (p & 0x0000ff);

                rinsum += sir[0];
                ginsum += sir[1];
                binsum += sir[2];

                rsum += rinsum;
                gsum += ginsum;
                bsum += binsum;

                stackpointer = (stackpointer + 1) % div;
                sir = stack[(stackpointer) % div];

                routsum += sir[0];
                goutsum += sir[1];
                boutsum += sir[2];

                rinsum -= sir[0];
                ginsum -= sir[1];
                binsum -= sir[2];

                yi++;
            }
            yw += w;
        }
        for (x = 0; x < w; x++) {
            rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
            yp = -radius * w;
            for (i = -radius; i <= radius; i++) {
                yi = Math.max(0, yp) + x;

                sir = stack[i + radius];

                sir[0] = r[yi];
                sir[1] = g[yi];
                sir[2] = b[yi];

                rbs = r1 - Math.abs(i);

                rsum += r[yi] * rbs;
                gsum += g[yi] * rbs;
                bsum += b[yi] * rbs;

                if (i > 0) {
                    rinsum += sir[0];
                    ginsum += sir[1];
                    binsum += sir[2];
                } else {
                    routsum += sir[0];
                    goutsum += sir[1];
                    boutsum += sir[2];
                }

                if (i < hm) {
                    yp += w;
                }
            }
            yi = x;
            stackpointer = radius;
            for (y = 0; y < h; y++) {
                // Preserve alpha channel: ( 0xff000000 & pix[yi] )
                pix[yi] = (0xff000000 & pix[yi]) | (dv[rsum] << 16) | (dv[gsum] << 8) | dv[bsum];

                rsum -= routsum;
                gsum -= goutsum;
                bsum -= boutsum;

                stackstart = stackpointer - radius + div;
                sir = stack[stackstart % div];

                routsum -= sir[0];
                goutsum -= sir[1];
                boutsum -= sir[2];

                if (x == 0) {
                    vmin[y] = Math.min(y + r1, hm) * w;
                }
                p = x + vmin[y];

                sir[0] = r[p];
                sir[1] = g[p];
                sir[2] = b[p];

                rinsum += sir[0];
                ginsum += sir[1];
                binsum += sir[2];

                rsum += rinsum;
                gsum += ginsum;
                bsum += binsum;

                stackpointer = (stackpointer + 1) % div;
                sir = stack[stackpointer];

                routsum += sir[0];
                goutsum += sir[1];
                boutsum += sir[2];

                rinsum -= sir[0];
                ginsum -= sir[1];
                binsum -= sir[2];

                yi += w;
            }
        }

        bitmap.setPixels(pix, 0, w, 0, 0, w, h);

        return (bitmap);
    }
}

算法就是這樣了，不要問我懂不懂，你懂的。

使用

如何在程序中使用呢，也很簡單：

package com.xys.blur;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.view.View;
import android.view.ViewTreeObserver.OnPreDrawListener;
import android.widget.ImageView;

public class Test extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		final ImageView imageView = (ImageView) findViewById(R.id.image1);

		final Bitmap bitmap = BitmapFactory.decodeResource(getResources(),
				R.drawable.blur);

		imageView.getViewTreeObserver().addOnPreDrawListener(
				new OnPreDrawListener() {

					@Override
					public boolean onPreDraw() {
						blur(bitmap, imageView);
						return true;
					}
				});
	}

	private void blur(Bitmap bkg, View view) {
		long startMs = System.currentTimeMillis();
		float scaleFactor = 8;
		float radius = 2;

		Bitmap overlay = Bitmap.createBitmap(
				(int) (view.getMeasuredWidth() / scaleFactor),
				(int) (view.getMeasuredHeight() / scaleFactor),
				Bitmap.Config.ARGB_8888);
		Canvas canvas = new Canvas(overlay);
		canvas.translate(-view.getLeft() / scaleFactor, -view.getTop()
				/ scaleFactor);
		canvas.scale(1 / scaleFactor, 1 / scaleFactor);
		Paint paint = new Paint();
		paint.setFlags(Paint.FILTER_BITMAP_FLAG);
		canvas.drawBitmap(bkg, 0, 0, paint);

		overlay = FastBlur.doBlur(overlay, (int) radius, true);
		view.setBackground(new BitmapDrawable(getResources(), overlay));
		System.out.println(System.currentTimeMillis() - startMs + "ms");
	}
}

為什麼我們要在addOnPreDrawListener中來調用blur方法呢，看我前面的文章的朋友應該會知道，這樣做是為了能夠在onCreate中獲取控件尺寸，通過scaleFactor和radius兩個參數，我們來控制Blur的程度。

代碼中還有幾點需要解釋下：

1、我們為什麼要通過scaleFactor來縮小圖片：由於在做Blur的時候，圖片精度本來就要降低，那麼我們為什麼不先降低精度再去處理呢，這樣的效果就是巨大的縮小了生成時間

2、我們給Paint提供了FILTER_BITMAP_FLAG標示，這樣的話在處理bitmap縮放的時候，就可以達到雙緩沖的效果，模糊處理的過程就更加順暢了

3、如果我們要做某一部分的Blur效果，一般是將這部分圖片裁減下來，然後Blur後設給某個控件的背景

最終效果如下：

效果已經出來了，Demo很簡單，只是為了演示使用方法。

以上。