效果圖：

程式碼

MyBitmapTwo

package com.example.administrator.mywidgetmode.Bitmapview;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ComposePathEffect;
import
 
 android.graphics.CornerPathEffect;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import
 
 android.view.View;
import android.view.Window;

import com.example.administrator.mywidgetmode.R;

/**
 * Created by Administrator on 2015/9/17.
 */
public class MyBitmapTwo extends View{
    private int width;
    private int height;
    private Bitmap mBitmap;
    private Paint mPaintCircel;
    private
 
 Paint mPaintRect;
    private Canvas canvasBit;
    private Bitmap mBitmapBackground;
    private Matrix matrix;
    public MyBitmapTwo(Context context) {
        super(context);
    }

    public MyBitmapTwo(Context context, AttributeSet attrs) {
        super(context, attrs);

        path=new Path();

        mBitmapBackground=BitmapFactory.decodeResource(getResources(),R.mipmap.d);

        matrix=new Matrix();
        //黃色畫筆
        mPaintCircel=new Paint();
        mPaintCircel.setColor(Color.YELLOW);
        //綠色畫筆
        mPaintRect=new Paint();
        mPaintRect.setColor(Color.GREEN);
        //圖形交叉
        PorterDuffXfermode mode=new PorterDuffXfermode(PorterDuff.Mode.XOR);//交叉的部分顯示背景
        mPaintCircel.setXfermode(mode);
        //移動時用線
        mPaintCircel.setStrokeJoin(Paint.Join.ROUND);//設定線段中間用圓形填充
        mPaintCircel.setStrokeCap(Paint.Cap.ROUND);//設定線段開頭是圓形
        mPaintCircel.setStrokeWidth(50);
        mPaintCircel.setStyle(Paint.Style.FILL_AND_STROKE);//非空心
        mPaintCircel.setPathEffect(new CornerPathEffect(360));
        mPaintCircel.setAntiAlias(true);//消鋸齒

    }
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        width = getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec);
        height = getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec);
        setMeasuredDimension(width, height);//設定畫布的大小，長和寬

        mBitmap = Bitmap.createBitmap(width,height, Bitmap.Config.ARGB_8888);
        canvasBit=new Canvas(mBitmap);

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawBitmap(mBitmapBackground,new Rect(0,0,mBitmapBackground.getWidth(),mBitmapBackground.getHeight()),new Rect(0,0,width,height),null);//用圖片做背景
        //canvas.drawColor(Color.RED);//設定背景色
        canvasBit.drawRect(0,0,width,height,mPaintRect);//跟view大小一樣的綠色矩形
        canvasBit.drawPath(path,mPaintCircel);//按路徑畫圖形，
        // 這裡要注意，畫筆必須得是得到圖形交叉模式的畫筆 PorterDuffXfermode mode=new PorterDuffXfermode(PorterDuff.Mode.XOR);mPaintCircel.setXfermode(mode);

        canvas.drawBitmap(mBitmap, 0, 0, null);
    }
    float x;
    float y;
    float old_x;
    float old_y;
    private Path path;
    @Override//點選事件
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                x=event.getX();
                y=event.getY();
              path.moveTo(x,y);
                invalidate();
                old_x=x;
                old_y=y;
                return true;
            case MotionEvent.ACTION_MOVE:
                x=event.getX();
                y=event.getY();
              path.moveTo(old_x,old_y);
                path.lineTo(x,y);
//                path.quadTo((x+old_x)/2,(y+old_y)/2,x,y);//跟上面的lineTo效果一樣
                invalidate();
                old_x=x;
                old_y=y;
                return true;
        }
        return super.onTouchEvent(event);
    }
}

MyBitmapTwoActivity

package com.example.administrator.mywidgetmode.Bitmapview;

import android.graphics.Bitmap;
import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;

import com.example.administrator.mywidgetmode.R;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

/**
 * Created by Administrator on 2015/9/17.
 */
public class MyBitmapTwoActivity extends AppCompatActivity {
    private Button mBt;
    private MyBitmapTwo myBitmapTwo;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_bitmap_two);
        myBitmapTwo= (MyBitmapTwo) findViewById(R.id.myBitmapTwo);
        mBt= (Button) findViewById(R.id.button_jpg);
        mBt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                myBitmapTwo.setDrawingCacheEnabled(true);
                Bitmap bitmap=myBitmapTwo.getDrawingCache(true);
                File file=new File(Environment.getExternalStorageDirectory(),System.currentTimeMillis()+".jpg");
                if(!file.exists()){
                    try {
                        file.createNewFile();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    try {
                        bitmap.compress(Bitmap.CompressFormat.JPEG,100,new FileOutputStream(file));
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    }
                }
            }
        });
    }
}

layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <Button
        android:id="@+id/button_jpg"
        android:text="儲存圖片"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <com.example.administrator.mywidgetmode.Bitmapview.MyBitmapTwo
        android:id="@+id/myBitmapTwo"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

更換背景

自己寫一個values

myview_attr

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="myview">
        <attr name="myview_backgroud" format="reference"></attr>
        <attr name="myview_paintwidth" format="dimension|reference"></attr>
    </declare-styleable>
</resources>

layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:myview="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <Button
        android:id="@+id/button_jpg"
        android:text="儲存圖片"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <com.example.administrator.mywidgetmode.Bitmapview.MyBitmapTwo
        android:id="@+id/myBitmapTwo"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        myview:myview_backgroud="@mipmap/b"
        myview:myview_paintwidth="30dp"/>
</LinearLayout>

MyBitmapTwo
在重寫MyBitmapTwo方法里加入下面的程式碼，更換背景，和自定義畫筆的大小

 final TypedArray typedArray=context.obtainStyledAttributes(attrs,R.styleable.myview);
        BitmapDrawable dra = (BitmapDrawable) typedArray.getDrawable(R.styleable.myview_myview_backgroud);
        if (dra!=null){
            Log.d("drawable",""+dra.getIntrinsicWidth());
            mBitmapBackground=dra.getBitmap();
        }else {
            mBitmapBackground=BitmapFactory.decodeResource(getResources(),R.mipmap.d);
        }
        int paintWidth=typedArray.getDimensionPixelOffset(R.styleable.myview_myview_paintwidth,30);