android 仿微信群聊头像 合成图片，微信中可以显示出群头像为多个用户的头像网格，这里讲方法已经封装好，
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先看效果：
使用例子：
@Overridepublic void onClick(View v) {PNUtils.runThread(new Runnable() {@Overridepublic void run() {Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.cx_facebook_icon);Bitmap bitmap1 = BitmapFactory.decodeResource(getResources(), R.mipmap.cx_google_icon);Bitmap bitmap3 = BitmapFactory.decodeResource(getResources(), R.mipmap.cx_twitter);Bitmap bitmap4 = BitmapFactory.decodeResource(getResources(), R.mipmap.cx_weixin_icon);List<Bitmap> bitmaps=new ArrayList<>();bitmaps.add(bitmap);bitmaps.add(bitmap1);bitmaps.add(bitmap3);bitmaps.add(bitmap4);final Bitmap bitmap2=PNUtils.createHeaderBitmap(bitmaps, 300, 300, 2, "#000000");runOnUiThread(new Runnable() {@Overridepublic void run() {imageView.setImageBitmap(bitmap2);}});}});}public static Bitmap createHeaderBitmap(List<Bitmap> bitmaps,int maxWidth,int maxHeight, int columnNums, String backgroundColor) {if (bitmaps.size()==0)return null;int itemWidth=maxWidth/columnNums;int itemHeight=maxHeight/columnNums;int rows=-1;Bitmap bitmap2 = Bitmap.createBitmap(maxWidth, maxHeight, Bitmap.Config.ARGB_8888);Canvas canvas=new Canvas(bitmap2);canvas.drawColor(Color.parseColor(backgroundColor));for (int i=0; i<bitmaps.size(); i++) {int column=i%columnNums;if (column==0)rows++;canvas.drawBitmap(resizeBitmap(bitmaps.get(i), itemWidth), column*itemWidth, rows*itemHeight, null);}return bitmap2;}/*** 重新修改图片大小*/public static Bitmap resizeBitmap(Bitmap bitmap, int newWidth) {float scaleWidth = ((float) newWidth) / bitmap.getWidth();Matrix matrix = new Matrix();matrix.postScale(scaleWidth, scaleWidth);Bitmap bmpScale = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);return bmpScale;}
