方法一：

/*    实现思维是这样的：    1.首先拿到bitmap图片    2.得到bitmap图片的高度 宽度，并且计算好各个画图尺寸    3.创建一个空白的 bitmap图片： Bitmap output = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);    4.将这个空白图片导入画布里    5.然后重点： 这个画布一定是要设置成透明的    6.在这张透明的画布上画圆型。    7.然后重点：设置相差裁剪属性    8.然后在这张透明的画布上添加bitmap图片    9.返回那张透明的bitmap     */    public Bitmap toRoundBitmap(Bitmap bitmap) {        int width = bitmap.getWidth();        int height = bitmap.getHeight();        float roundPx;        float left, top, right, bottom, dst_left, dst_top, dst_right, dst_bottom;        if (width <= height) {            roundPx = width / 2;            left = 0;            top = 0;            right = width;            bottom = width;            height = width;            dst_left = 0;            dst_top = 0;            dst_right = width;            dst_bottom = width;        } else {            roundPx = height / 2;            float clip = (width - height) / 2;            left = clip;            right = width - clip;            top = 0;            bottom = height;            width = height;            dst_left = 0;            dst_top = 0;            dst_right = height;            dst_bottom = height;        }        Bitmap output = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);        Canvas canvas = new Canvas(output);        final int color = 0xff424242;        final Paint paint = new Paint();        final Rect src = new Rect((int) left, (int) top, (int) right, (int) bottom);        final Rect dst = new Rect((int) dst_left, (int) dst_top, (int) dst_right, (int) dst_bottom);        final RectF rectF = new RectF(dst);        paint.setAntiAlias(true);// 设置画笔无锯齿        canvas.drawARGB(0, 0, 0, 0); // 填充整个Canvas        paint.setColor(color);        // 以下有两种方法画圆,drawRounRect和drawCircle        // canvas.drawRoundRect(rectF, roundPx, roundPx, paint);// 画圆角矩形，第一个参数为图形显示区域，第二个参数和第三个参数分别是水平圆角半径和垂直圆角半径。        canvas.drawCircle(roundPx, roundPx, roundPx, paint);        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));// 设置两张图片相交时的模式,参考http://trylovecatch.iteye.com/blog/1189452        canvas.drawBitmap(bitmap, src, dst, paint); //以Mode.SRC_IN模式合并bitmap和已经draw了的Circle        return output;    }

参考流程图 &  原理图：

方法二：

转：

使用clipPath()方法裁剪圆形图片。

首先，我们先看效果图：

裁剪前：

裁剪后：

接下来，我们来一步一步的实现。

1.新建一个module

2.新建一个自定义view类，继承View,并重写两参构造器和onDrawn方法

/** * Created by zhaoxin on 17/8/31. */public class MyAnimationView extends View {    public MyAnimationView(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);    }

 

3.新建一个布局，在布局中通过包名.类导入自定义view

 

4.接下来就是重要的裁剪圆形图片部分

/** * Created by zhaoxin on 17/8/31. */public class MyAnimationView extends View {    private Bitmap mBitmap；    private Path mPath;    public MyAnimationView(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        Paint paint = new Paint();        mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.pic);        mPath = new Path();        mPath.addCircle(mBitmap.getWidth() / 2, mBitmap.getHeight() / 2, mBitmap.getWidth() / 2, Path.Direction.CCW);        canvas.clipPath(mPath);        canvas.drawBitmap(mBitmap, 0, 0, paint);    }}

 

个人重写

/*content:圆形图片的自定义ImageViewtime:2018-8-7 17：43build:zhouqiang使用方法：请用setImage 方法设置图片 */public class CircleImageView extends View {    private Path mPath;    private Paint mPaint;    private Bitmap mBitmap;    public CircleImageView(Context context) {        super(context);        initPaint();    }    public CircleImageView(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);        initPaint();    }    public CircleImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        initPaint();    }    public void initPaint(){        mPaint = new Paint();        mPath = new Path();    }    public void setImage(Bitmap bitmap){        this.mBitmap = bitmap;    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        mPaint.reset();        mPath.addCircle(getHeight()/2,getWidth()/2,getWidth()/2.5f,Path.Direction.CW);        mPaint.setAntiAlias(true);        mPaint.setStyle(Paint.Style.FILL);        canvas.clipPath(mPath);        canvas.drawBitmap(mBitmap,                new Rect(0,0,mBitmap.getWidth(),mBitmap.getHeight()),                new Rect(0,0,getWidth(),getHeight()),                mPaint);    }}