android开发步步为营之58:给图片绘制圆形气泡背景效果

           最近在开发项目的时候，有一个需求，需要给应用图标绘制圆形气泡背景，有了彩色气泡这样显得漂亮一点，气泡的颜色是应用图标的颜色均值，先看看效果，然后，我再给出demo。

           demo应用图标是这样的：

          

          添加气泡背景后是这样的：

         

         仔细看圆形背景颜色是图标颜色的均值。

         好的，下面我们来完成这个demo。

         第一步、编写页面activity_drawcycle.xml

         

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical" >    <ImageView        android:id="@+id/imgCycle"        android:layout_width="40dp"        android:layout_height="40dp"        android:src="@drawable/ic_launcher" /></LinearLayout>

         第二步、编写Activity,DrawCycleActivity.java

/** *  */package com.figo.study;import com.figo.study.utils.UIUtils;import android.app.Activity;import android.content.Context;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.PixelFormat;import android.graphics.PorterDuffXfermode;import android.graphics.Bitmap.Config;import android.graphics.RectF;import android.graphics.drawable.BitmapDrawable;import android.graphics.drawable.Drawable;import android.os.Bundle;import android.widget.ImageView;/** * @author figo *  */public class DrawCycleActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_drawcycle);                //需要给该图片绘制圆形气泡背景Drawable img = getResources().getDrawable(R.drawable.ic_launcher);//绘制圆形气泡Bitmap bp = createCircleImage(drawableToBitmap(img),40);                //绘制好的图片赋值给ImageView控件ImageView imgView = (ImageView) findViewById(R.id.imgCycle);imgView.setImageDrawable(new BitmapDrawable(bp));}private Bitmap drawableToBitmap(Drawable drawable){Bitmap bitmap=null;try {bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(),drawable.getIntrinsicHeight(),drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888: Bitmap.Config.RGB_565);Canvas canvas = new Canvas(bitmap);drawable.setBounds(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());drawable.draw(canvas);} catch (Exception e) {// TODO: handle exception}return bitmap;}private Bitmap createCircleImage(Bitmap source, int sizeDp) {final Paint paint = new Paint();final int nw = source.getWidth();        final int nh = source.getHeight();        //计算源图片颜色平均值，然后将该平均值颜色作为气泡颜色        int[] pixels = new int[nw * nh];        source.getPixels(pixels, 0, nw, 0, 0, nw, nh);        long rtotal=0;        long gtotal=0;        long btotal=0;        for (int i = 0; i < pixels.length; i++) {            int p = pixels[i];            int r = (p & 0x00FF0000) >> 16;            int g = (p & 0x0000FF00) >> 8;            int b = (p & 0x000000FF) >> 0;            rtotal+=r;            gtotal+=g;            btotal+=b;        }        int rAverage=(int) (rtotal / (nw * nh));        int gAverage=(int) (gtotal / (nw * nh));        int bAverage=(int) (btotal / (nw * nh));        //设置画笔颜色paint.setColor(Color.argb(255, rAverage, gAverage, bAverage));paint.setAntiAlias(true);int sizePix=UIUtils.dip2px(DrawCycleActivity.this,sizeDp);Bitmap target = Bitmap.createBitmap(sizePix, sizePix, Config.ARGB_8888);//绘制正方形画布Canvas canvas = new Canvas(target);        //在正方形里面绘制圆形canvas.drawCircle(sizePix/2, sizePix/2, sizePix / 2, paint);//图片相交模式，canvas原有的图片 可以理解为背景 就是dst，新画上去的图片 可以理解为前景 就是src//SRC_OVER就是新画上去的图片在canvas之上paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.SRC_OVER));        //计算目标图形的左上角和右下角的坐标RectF dst=new RectF();        //圆形内置正方形（即将绘制的图片区域）的边长float destRectWidth= (float)Math.sqrt((sizeDp*sizeDp/2));float left= (sizeDp-destRectWidth)/2+1;//空1dpfloat top=left;float right=sizeDp-left;float bottom=right;//dst.set(UIUtils.dip2px(DrawCycleActivity.this, 5.86f), UIUtils.dip2px(DrawCycleActivity.this,5.86f), UIUtils.dip2px(DrawCycleActivity.this,34.14f), UIUtils.dip2px(DrawCycleActivity.this,34.14f));dst.set(UIUtils.dip2px(DrawCycleActivity.this,left), UIUtils.dip2px(DrawCycleActivity.this,top), UIUtils.dip2px(DrawCycleActivity.this,right),UIUtils.dip2px(DrawCycleActivity.this,bottom));canvas.drawBitmap(source, null, dst, paint);return target;}}