ImageView圆角

activity_main.xml

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:CustomImageView="http://schemas.android.com/apk/res/com.example.customview05imageview"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

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

        <com.example.customview05imageview.RoundImageView
            android:layout_width="wrap_content"
            android:layout_margin="5dp"
            android:layout_height="wrap_content"
            android:src="@drawable/icon" />
        
        <ImageView
          android:id="@+id/imageview"
            android:layout_margin="5dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/icon" />

        <com.example.customview05imageview.view.CustomImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="10dp"
            CustomImageView:src="@drawable/icon"
            CustomImageView:type="circle" />

        <com.example.customview05imageview.view.CustomImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="10dp"
            CustomImageView:borderRadius="10dp"
            CustomImageView:src="@drawable/icon"
            CustomImageView:type="round" />

        <com.example.customview05imageview.view.CustomImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="10dp"
            CustomImageView:borderRadius="20dp"
            CustomImageView:src="@drawable/icon"
            CustomImageView:type="round" />
    </LinearLayout>

</ScrollView>

MainActivity

package com.example.customview05imageview;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.widget.ImageView;

public class MainActivity extends Activity
{

	private ImageView imageview;
	@Override
	protected void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		imageview = (ImageView) findViewById(R.id.imageview);
		
		Drawable drawable = getResources().getDrawable(R.drawable.icon);  
        BitmapDrawable bitmapDrawable = (BitmapDrawable) drawable;  
        Bitmap bitmap = bitmapDrawable.getBitmap();  
        Bitmap roundCorner = toRoundCorner(bitmap, 30);
        imageview.setImageBitmap(roundCorner);
	}
	public static Bitmap toRoundCorner(Bitmap bitmap, int pixels) {  
		//创建bitmap对象
        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),  
                bitmap.getHeight(), Config.ARGB_8888);  
        //创建画笔、画布
        Canvas canvas = new Canvas(output);  
        final Paint paint = new Paint();  
        final int color = 0xff424242;  
        //创建矩形-位置
        final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());  
        final RectF rectF = new RectF(rect);  
        //圆角
        final float roundPx = pixels;  
        paint.setAntiAlias(true); 
        //透明
        canvas.drawARGB(0, 0, 0, 0);  
        paint.setColor(color);  
        
        canvas.drawRoundRect(rectF, roundPx, roundPx, paint);  
        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));  
        canvas.drawBitmap(bitmap, rect, rect, paint);  
        return output;  
    }  

}

CustomImageView

package com.example.customview05imageview.view;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.View;

import com.example.customview05imageview.R;

public class CustomImageView extends View {

	private int type;
	private static final int TYPE_CIRCLE = 0;
	private static final int TYPE_ROUND = 1;

	private Bitmap mSrc;
	private int mRadius;
	private int mWidth;
	private int mHeight;

	/**
	 * 初始化一些自定义的参数
	 */
	public CustomImageView(Context context, AttributeSet attrs) {
		this(context, attrs, 0);
	}

	public CustomImageView(Context context) {
		this(context, null);
	}

	public CustomImageView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);

		TypedArray a = context.obtainStyledAttributes(attrs,
				R.styleable.CustomImageView, defStyle, 0);

		int n = a.getIndexCount();
		// 遍历属性
		for (int i = 0; i < n; i++) {
			int attr = a.getIndex(i);
			switch (attr) {
			case R.styleable.CustomImageView_src:
				mSrc = BitmapFactory.decodeResource(getResources(),
						a.getResourceId(attr, 0));
				break;
			case R.styleable.CustomImageView_type:
				// 默认为Circle--0
				type = a.getInt(attr, 0);
				break;
			case R.styleable.CustomImageView_borderRadius:
				// 转变为标准尺寸的一个函数-- 默认为10DIP
				mRadius = a.getDimensionPixelSize(attr, (int) TypedValue
						.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 10f,
								getResources().getDisplayMetrics()));
				break;
			}
		}
		a.recycle();
	}

	/**
	 * 计算控件的高度和宽度
	 */
	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		/**
		 * 参数：它们指明控件可获得的空间以及关于这个空间描述的元数据 设置宽度
		 */
		int specMode = MeasureSpec.getMode(widthMeasureSpec);
		int specSize = MeasureSpec.getSize(widthMeasureSpec);

		/**
		 * MeasureSpec.EXACTLY是精确尺寸，当我们将控件的layout_width或layout_height指定为具体数值时如andorid:layout_width="50dip"
		 * 或者为FILL_PARENT是，都是控件大小已经确定的情况，都是精确尺寸。
		 */
		if (specMode == MeasureSpec.EXACTLY)// match_parent
		{
			mWidth = specSize;
		} else {
			// 由图片决定的宽
			int desireByImg = getPaddingLeft() + getPaddingRight()
					+ mSrc.getWidth();
			if (specMode == MeasureSpec.AT_MOST)// wrap_content
			{
				/**
				 * 此时控件尺寸只要不超过父控件允许的最大尺寸即可
				 */
				mWidth = Math.min(desireByImg, specSize);
			} else

				mWidth = desireByImg;
		}

		/***
		 * 设置高度
		 */

		specMode = MeasureSpec.getMode(heightMeasureSpec);
		specSize = MeasureSpec.getSize(heightMeasureSpec);
		if (specMode == MeasureSpec.EXACTLY)// match_parent , accurate
		{
			mHeight = specSize;
		} else {
			int desire = getPaddingTop() + getPaddingBottom()
					+ mSrc.getHeight();

			if (specMode == MeasureSpec.AT_MOST)// wrap_content
			{
				mHeight = Math.min(desire, specSize);
			} else
				mHeight = desire;
		}

		setMeasuredDimension(mWidth, mHeight);

	}

	/**
	 * 绘制
	 */
	@Override
	protected void onDraw(Canvas canvas) {
		switch (type) {
		case TYPE_CIRCLE:
			int min = Math.min(mWidth, mHeight);
			// Bitmap 创建 一个新的，缩放后的 Bitmap
			mSrc = Bitmap.createScaledBitmap(mSrc, min, min, false);
			//在某个位置画圆
			canvas.drawBitmap(createCircleImage(mSrc, min), 0, 0, null);
			break;
		case TYPE_ROUND:
			canvas.drawBitmap(createRoundConerImage(mSrc), 0, 0, null);
			break;

		}

	}

	/**
	 * 根据原图和变长绘制圆形图片
	 */
	private Bitmap createCircleImage(Bitmap source, int min) {
		final Paint paint = new Paint();
		paint.setAntiAlias(true);
		//该函数创建一个带有特定宽度、高度和颜色格式的位图
		Bitmap target = Bitmap.createBitmap(min, min, Config.ARGB_8888);
		//产生一个同样大小的画布
		Canvas canvas = new Canvas(target);
		//首先绘制圆形-原心xy坐标以及半径
		canvas.drawCircle(min / 2, min / 2, min / 2, paint);
		//取两层绘制交集。显示上层
		paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
		//绘制图片
		canvas.drawBitmap(source, 0, 0, paint);
		return target;
	}

	/**
	 * 根据原图添加圆角
	 */
	private Bitmap createRoundConerImage(Bitmap source) {
		final Paint paint = new Paint();
		paint.setAntiAlias(true);
		Bitmap target = Bitmap.createBitmap(mWidth, mHeight, Config.ARGB_8888);
		Canvas canvas = new Canvas(target);
		RectF rect = new RectF(0, 0, source.getWidth(), source.getHeight());
		canvas.drawRoundRect(rect, mRadius, mRadius, paint);
		paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
		canvas.drawBitmap(source, 0, 0, paint);
		return target;
	}
}

RoundImageView

package com.example.customview05imageview;
 
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.widget.ImageView;
 
public class RoundImageView extends ImageView {
 
    public RoundImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }
 
    public RoundImageView(Context context) {
        super(context);
        init();
    }
    
    private void init() {
    	maskPaint.setAntiAlias(true);
    	maskPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
    	//
    	zonePaint.setAntiAlias(true);
    	zonePaint.setColor(Color.RED);
    	//
    	float density = getResources().getDisplayMetrics().density;
    	rect_adius = rect_adius * density;
    }
    
    @Override
    protected void onLayout(boolean changed, int left, int top, int right,
            int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        int w = getWidth();
        int h = getHeight();
        roundRect.set(0, 0, w, h);
    }
    private final RectF roundRect = new RectF();
    
    private float rect_adius = 20;
    private final Paint maskPaint = new Paint();
    private final Paint zonePaint = new Paint();
 

 
    @Override
    public void draw(Canvas canvas) {
        canvas.saveLayer(roundRect, zonePaint, Canvas.ALL_SAVE_FLAG);
        //产生一个红色的圆角矩形
        canvas.drawRoundRect(roundRect, rect_adius, rect_adius, zonePaint);
        //
        canvas.saveLayer(roundRect, maskPaint, Canvas.ALL_SAVE_FLAG);
        super.draw(canvas);
        canvas.restore();
    }
 
}