看到很多人开发过程中要使用圆角图片时，解决方法有：1.重新绘制一张图片2.通过布局来配置3.通过重写View来实现其中1，2在这里就不讲了，重点讲讲方法三的实现。
实现一：通过截取画布一个圆形区域与图片的相交部分进行绘制，缺点：锯齿明显，设置Paint,Canvas抗锯齿无效。
package com.open.circleimageview.widget;import android.content.Context;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.PaintFlagsDrawFilter;import android.graphics.Path;import android.graphics.Rect;import android.graphics.Region;import android.util.AttributeSet;import android.view.View;public class CircleImageViewA extends View {public CircleImageViewA(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);}public CircleImageViewA(Context context, AttributeSet attrs) {super(context, attrs);}public CircleImageViewA(Context context) {super(context);}private Bitmap bitmap;private Rect bitmapRect=new Rect();private PaintFlagsDrawFilter pdf=new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG|Paint.FILTER_BITMAP_FLAG);private Paint paint = new Paint();{paint.setStyle(Paint.Style.STROKE);paint.setFlags(Paint.ANTI_ALIAS_FLAG);paint.setAntiAlias(true);// 设置画笔的锯齿效果。 true是去除，大家一看效果就明白了}private Path mPath=new Path();public void setImageBitmap(Bitmap bitmap){this.bitmap=bitmap;}@Overrideprotected void onDraw(Canvas canvas) {if(null==bitmap){return;}bitmapRect.set(0, 0, getWidth(), getHeight());canvas.save();canvas.setDrawFilter(pdf);mPath.reset();canvas.clipPath(mPath); // makes the clip emptymPath.addCircle(getWidth()/2, getWidth()/2, getHeight()/2, Path.Direction.CCW);canvas.clipPath(mPath, Region.Op.REPLACE);canvas.drawBitmap(bitmap, null, bitmapRect, paint);canvas.restore();}}实现二：通过PorterDuffXfermode 方式（注意要设置硬件加速，否则部分机子无效），优点：锯齿基本没有package com.open.circleimageview.widget;import android.content.Context;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.PaintFlagsDrawFilter;import android.graphics.PorterDuff;import android.graphics.PorterDuffXfermode;import android.graphics.Rect;import android.graphics.RectF;import android.util.AttributeSet;import android.view.View;public class CircleImageViewB extends View {public CircleImageViewB(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);init();}public CircleImageViewB(Context context, AttributeSet attrs) {super(context, attrs);init();}public CircleImageViewB(Context context) {super(context);init();}private Bitmap bitmap;private Rect bitmapRect=new Rect();private PaintFlagsDrawFilter pdf=new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG|Paint.FILTER_BITMAP_FLAG);private Paint paint = new Paint();{paint.setStyle(Paint.Style.STROKE);paint.setFlags(Paint.ANTI_ALIAS_FLAG);paint.setAntiAlias(true);// 设置画笔的锯齿效果。 true是去除，大家一看效果就明白了}private Bitmap mDstB=null;private PorterDuffXfermode xfermode=new PorterDuffXfermode(PorterDuff.Mode.MULTIPLY);private void init(){try {if(android.os.Build.VERSION.SDK_INT>=11){setLayerType(LAYER_TYPE_SOFTWARE, null);}} catch (Exception e) {e.printStackTrace();}}public void setImageBitmap(Bitmap bitmap){this.bitmap=bitmap;}private Bitmap makeDst(int w, int h){Bitmap bm = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);Canvas c = new Canvas(bm);Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);p.setColor(Color.parseColor("#ffffffff"));c.drawOval(new RectF(0, 0, w, h), p);return bm;}@Overrideprotected void onDraw(Canvas canvas) {if(null==bitmap){return;}if(null==mDstB){mDstB=makeDst(getWidth(), getHeight());}bitmapRect.set(0, 0, getWidth(), getHeight());canvas.save();canvas.setDrawFilter(pdf);canvas.drawBitmap(mDstB, 0, 0, paint);paint.setXfermode(xfermode);canvas.drawBitmap(bitmap, null, bitmapRect, paint);paint.setXfermode(null);canvas.restore();}}效果图如下：
代码地址：
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