Android图像处理（二）画画板

朴灿烈づ我的快乐病毒、 2022-08-22 05:55 132阅读 0赞

*   *  思路
     *  布局
     *  代码

## 思路： ##

建立一个bitmap副本  
给imageview设置触摸监听  
在两个触摸点之间画一条线`canvas.drawLine(mStartx,mStarty,x,y,mPaint)`  
然后`mImageView.setImageBitmap(mAltBitmap);`  
可以设置不同画笔颜色，粗细等  
也可以改变画布颜色。

## 布局： ##

## 代码： ##

cn.zsp.huahuaban;
    import android.graphics.Bitmap;
    import android.graphics.BitmapFactory;
    import android.graphics.Canvas;
    import android.graphics.Color;
    import android.graphics.Matrix;
    import android.graphics.Paint;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.util.Log;
    import android.view.MotionEvent;
    import android.view.View;
    import android.widget.ImageView;
    
    public class MainActivity extends AppCompatActivity {
        private static final String TAG = "zsp";
     private ImageView mImageView;
     private Paint mPaint;
     private Bitmap mAltBitmap;
     private int mStarty;
     private int mStartx;
    
      @Override
      protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      mImageView = (ImageView) findViewById(R.id.iv);
      //得到原图
      Bitmap bitmap= BitmapFactory.decodeResource(getResources(),R.drawable.sc);
      mImageView.setImageBitmap(bitmap);
      //获取副本
      mAltBitmap = Bitmap.createBitmap(bitmap.getWidth(),bitmap.getHeight(),bitmap.getConfig());
      mPaint = new Paint();
      mPaint.setColor(Color.BLACK);
      mPaint.setStyle(Paint.Style.FILL);
      //    mPaint.setStrokeWidth(20);
      final Canvas canvas=new Canvas(mAltBitmap);
      canvas.drawBitmap(bitmap,new Matrix(),mPaint);
      canvas.drawText("niafdsaf",0,0,mPaint);
      mImageView.setOnTouchListener(new View.OnTouchListener() {
    
                @Override
      public boolean onTouch(View v, MotionEvent event) {
                    switch (event.getAction()){
                        case MotionEvent.ACTION_DOWN:
                            Log.e(TAG, "onTouch: 按下了" );
      mStartx = (int) event.getX();
      mStarty = (int) event.getY();
     break; case MotionEvent.ACTION_MOVE:
                            Log.e(TAG, "onTouch: 移动了" );
     int x= (int) event.getX();
     int y= (int) event.getY();
      canvas.drawLine(mStartx,mStarty,x,y,mPaint);//两点间划线
      mImageView.setImageBitmap(mAltBitmap);
      mStartx=x;
      mStarty=y;//重置
      break;
     case MotionEvent.ACTION_UP:
                            Log.e(TAG, "onTouch: 离开了" );
     break; }
                    return true;
      }
            });
    
      }
    }
    </pre>