干货分享，图片模糊算法，解析xml绘制图片

项目需求：有一个xml文件，记录了一张图片每个元素的位置，大小，样式信息。

通过XmlResourceParser解析xml文件，得到每个元素的属性。

然后使用Paint绘制元素到Canvas上，得到一张Bitmap位图

将位图模糊处理，处理算法的原理(取图片上每个像素点周围的8个点平均值)

模糊算法：

package com.metek.blur;

import android.content.Context;
import android.graphics.Bitmap;

public class BlurUtils {
	/**
     * Android api 17实现的虚化
     * 某些机型上可能会Crash
     *
     * @param context
     * @param sentBitmap
     * @param radius     大于1小于等于25
     * @return
     */
    public static Bitmap fastblur(Context context,Bitmap sentBitmap,int radius) {
        if (sentBitmap == null) {
            return null;
        }
//        if (Build.VERSION.SDK_INT > 16) {
//            Bitmap bitmap = sentBitmap.copy(sentBitmap.getConfig(),true);
// 
//            final RenderScript rs = RenderScript.create(context);
//            final Allocation input = Allocation.createFromBitmap(rs,//                    sentBitmap,Allocation.MipmapControl.MIPMAP_NONE,//                    Allocation.USAGE_SCRIPT);
//            final Allocation output = Allocation.createTyped(rs,//                    input.getType());
//            final ScriptIntrinsicBlur script = ScriptIntrinsicBlur.create(rs,//                    Element.U8_4(rs));
//            script.setRadius(radius /* e.g. 3.f */);
//            script.setInput(input);
//            script.forEach(output);
//            output.copyTo(bitmap);
//            return bitmap;
//        }
        return stackblur(sentBitmap,radius);
    }
 
    /**
     * 纯Java实现的虚化，适用老版本api，外部只需调fastblur，会自动判断
     *
     * @param sentBitmap
     * @param radius
     * @return
     */
    private static Bitmap stackblur(Bitmap sentBitmap,int radius) {
 
        Bitmap bitmap = null;
        try {
            bitmap = sentBitmap.copy(sentBitmap.getConfig(),true);
        } catch (OutOfMemoryError e) {
            e.printStackTrace();
            return sentBitmap;
        }
 
        if (radius < 1) {
            return (null);
        }
 
        int w = bitmap.getWidth();
        int h = bitmap.getHeight();
 
        int[] pix = new int[w * h];
        bitmap.getPixels(pix,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,h);
        return (bitmap);
    }
}

package com.metek.blur;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;

import android.content.Context;
import android.content.res.XmlResourceParser;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.os.AsyncTask;
import android.os.SystemClock;
import android.util.DisplayMetrics;

/**
 * 生成天气模糊背景图
 * 
 */
public class BlurWeatherImage {
	private static final String TAG = "BlurWeatherImage";
	private Bitmap bitmap = null;
	private Paint paint;
	private Canvas canvas;
	private FileOutputStream out = null;
	private float wRate;
	private float hRate;
	private int width;
	private int height;
	private Context context;
	private static final String IMAGENAME="ani_cloudy_night.png";

	public BlurWeatherImage(Context context) {
		super();
		this.context = context;
		DisplayMetrics dm = context.getResources().getDisplayMetrics();
		width = dm.widthPixels;
		height = dm.heightPixels;
		bitmap = Bitmap.createBitmap(width,height,Bitmap.Config.ARGB_8888);
		paint = new Paint(Paint.ANTI_ALIAS_FLAG);
		canvas = new Canvas(bitmap);
		wRate = width / 720f;
		hRate = height / 1280f;
	}

	/** 模糊图片 */
	public void blurImage() {
		BulurAsyncTask bat = new BulurAsyncTask();
		bat.execute();
	}

	class BulurAsyncTask extends AsyncTask<Void,Void,Void> {
		protected Void doInBackground(Void... params) {
			analysisXml();
			return null;
		}

		protected void onPostExecute(Void result) {
			super.onPostExecute(result);
			listener.drawEnd();
		}

	}

	public void analysisXml() {
		canvas.drawColor(0xff102d37);
		XmlResourceParser parser = context.getResources().getXml(R.xml.ani_cloudy_night);
		try {
			int event = parser.getEventType();
			while (event != XmlResourceParser.END_DOCUMENT) {
				String tagName = parser.getName();
				if (event == XmlResourceParser.START_TAG) {
					if (tagName.equals("view")) {
						int x = Integer.parseInt(parser.getAttributeValue(null,"x"));
						int y = Integer.parseInt(parser.getAttributeValue(null,"y"));
						int w = Integer.parseInt(parser.getAttributeValue(null,"w"));
						int h = Integer.parseInt(parser.getAttributeValue(null,"h"));
						String residname = parser.getAttributeValue(null,"resid");
						int resid = context.getResources().getIdentifier(residname.replace("@drawable/",""),"drawable",context.getPackageName());
						picture(bitmap,h,resid);
						SystemClock.sleep(100);
					}
				}
				event = parser.next();
			}
		} catch (Exception e) {
			e.printStackTrace();
		}

		try {
			out = context.openFileOutput(IMAGENAME,Context.MODE_PRIVATE);
			bitmap.compress(Bitmap.CompressFormat.PNG,100,out);
			out = context.openFileOutput("blur_"+IMAGENAME,Context.MODE_PRIVATE);
			Bitmap blurBitmap = BlurUtils.fastblur(context,bitmap,80);
			blurBitmap.compress(Bitmap.CompressFormat.PNG,out);
			android.util.Log.i(TAG,IMAGENAME + "writer success");
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}
	}

	/**
	 * @param x
	 *            元素x坐标
	 * @param y
	 *            元素y坐标
	 * @param w
	 *            元素宽度
	 * @param h
	 *            元素高度
	 * @param resId
	 *            资源id
	 */
	public void picture(Bitmap bitmap,int x,int y,int w,int h,int resId) {
		Bitmap element = BitmapFactory.decodeResource(context.getResources(),resId);
		int scaleW = (int) (w * wRate);
		int scaleH = (int) (h * hRate);
		Bitmap scaled = Bitmap.createScaledBitmap(element,scaleW,scaleH,false);
		canvas.drawBitmap(scaled,x * wRate,y * hRate,paint);
	}

	private OnDrawListener listener;

	public interface OnDrawListener {
		/** 绘图结束 */
		public void drawEnd();
	}

	public void setOnDrawListener(OnDrawListener listener) {
		this.listener = listener;
	}
}

（编辑：李大同）

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