Android实现图片设置圆角形式

public class CircleImageView extends ImageView {
    private static final Xfermode MASK_XFERMODE;
    private Bitmap mask;
    private Paint paint;
    private int mBorderWidth = 10;
    private int mBorderColor = Color.parseColor("#f2f2f2");
    private boolean useDefaultStyle = false;

    static {
        PorterDuff.Mode localMode = PorterDuff.Mode.DST_IN;
        MASK_XFERMODE = new PorterDuffXfermode(localMode);
    }

    public CircleImageView(Context context) {
        super(context);
    }

    public CircleImageView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public CircleImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CircularImage);
        mBorderColor = a.getColor(R.styleable.CircularImage_border_color, mBorderColor);
        final int def = (int) (2 * context.getResources().getDisplayMetrics().density + 0.5f);
        mBorderWidth = a.getDimensionPixelOffset(R.styleable.CircularImage_border_width, def);
        a.recycle();
    }

    private void useDefaultStyle(boolean useDefaultStyle) {
        this.useDefaultStyle = useDefaultStyle;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if (useDefaultStyle) {
            super.onDraw(canvas);
            return;
        }
        final Drawable localDraw = getDrawable();
        if (localDraw == null) {
            return;
        }
        if (localDraw instanceof NinePatchDrawable) {
            return;
        }
        if (this.paint == null) {
            final Paint localPaint = new Paint();
            localPaint.setFilterBitmap(false);
            localPaint.setAntiAlias(true);
            localPaint.setXfermode(MASK_XFERMODE);
            this.paint = localPaint;
        }
        final int width = getWidth();
        final int height = getHeight();
        /** 保存layer */
        int layer = canvas.saveLayer(0.0F, 0.0F, width, height, null, 31);
        /** 设置drawable的大小 */
        localDraw.setBounds(0, 0, width, height);
        /** 将drawable绑定到bitmap(this.mask)上面（drawable只能通过bitmap显示出来） */
        localDraw.draw(canvas);
        if ((this.mask == null) || (this.mask.isRecycled())) {
            this.mask = createOvalBitmap(width, height);
        }
        /** 将bitmap画到canvas上面 */
        canvas.drawBitmap(this.mask, 0.0F, 0.0F, this.paint);
        /** 将画布复制到layer上 */
        canvas.restoreToCount(layer);
        drawBorder(canvas, width, height);
    }

    /**
     * 绘制圆形边框
     */
    private void drawBorder(Canvas canvas, final int width, final int height) {
        if (mBorderWidth == 0) {
            return;
        }
        final Paint mBorderPaint = new Paint();
        mBorderPaint.setStyle(Paint.Style.STROKE);
        mBorderPaint.setAntiAlias(true);
        mBorderPaint.setColor(mBorderColor);
        mBorderPaint.setStrokeWidth(mBorderWidth);
        canvas.drawCircle(width / 2, height / 2, (width - mBorderWidth) / 2, mBorderPaint);
        canvas = null;
    }

    public Bitmap createOvalBitmap(final int width, final int height) {
        Bitmap.Config localConfig = Bitmap.Config.ARGB_8888;
        Bitmap localBitmap = Bitmap.createBitmap(width, height, localConfig);
        Canvas localCanvas = new Canvas(localBitmap);
        Paint localPaint = new Paint();
        final int padding = (mBorderWidth - 3) > 0 ? mBorderWidth - 3 : 1;
        /**
         * 设置椭圆的大小(因为椭圆的最外边会和border的最外边重合的，如果图片最外边的颜色很深，有看出有棱边的效果，所以为了让体验更加好，
         * 让其缩进padding px)
         */
        RectF localRectF = new RectF(padding, padding, width - padding, height - padding);
        localCanvas.drawOval(localRectF, localPaint);
        return localBitmap;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="CircularImage">
        <attr name="border_width" format="dimension" />
        <attr name="border_color" format="color" />
    </declare-styleable>
</resources>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <ImageView
            android:layout_width="100dp"
            android:layout_height="100dp"
            android:src="@drawable/ic_sp" />

        <com.demo.test.bitmap.CircleImageView
            android:layout_width="100dp"
            android:layout_height="100dp"
            android:layout_marginLeft="50dp"
            android:src="@drawable/ic_sp" />
    </LinearLayout>
</LinearLayout>

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}