简单的手指绘图并保存所绘图片【源码】

public class SimpleFingerDraw extends Activity implements OnTouchListener,
    OnClickListener
{
  ImageView imageView;
  Button choosePicture, savePicture;
  Bitmap bitmap;
  Bitmap alteredBitmap;
  Canvas canvas;
  Paint paint;
  Matrix matrix;
  float downx = 0;
  float downy = 0;
  float upx = 0;
  float upy = 0;
  float top = 0, bottom = 0;
  String TAG = "FingerDraw";
  @Override
  protected void onCreate(Bundle savedInstanceState)
  {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    imageView = (ImageView) findViewById(R.id.ChosenImageView);
    choosePicture = (Button) findViewById(R.id.ChoosePictureButton);
    savePicture = (Button) findViewById(R.id.SavePictureButton);
    choosePicture.setOnClickListener(this);
    savePicture.setOnClickListener(this);
    savePicture.setVisibility(View.GONE);
  }
  @Override
  public boolean onTouch(View v, MotionEvent event)
  {
    // TODO Auto-generated method stub
    int action = event.getAction();
    switch (action)
    {
      case MotionEvent.ACTION_DOWN:
        downx = event.getX();// 获取的是以ImageView左上角为原点的坐标
        downy = event.getY();
        Log.e(TAG, "downx:" + downx + " downy:" + downy);
        break;
      case MotionEvent.ACTION_MOVE:
        upx = event.getX();
        upy = event.getY();
        canvas.drawLine(downx, downy, upx, upy, paint);
        imageView.invalidate();
        downx = upx;
        downy = upy;
        break;
      case MotionEvent.ACTION_UP:
        upx = event.getX();
        upy = event.getY();
        canvas.drawLine(downx, downy, upx, upy, paint);// 注意：这里是以图像的左上角为原点进行绘制直线
        imageView.invalidate();
        break;
      default:
        break;
    }
    return true;
  }
  @Override
  public void onClick(View v)
  {
    // TODO Auto-generated method stub
    if (v == choosePicture)
    {
      Intent choosePictureIntent = new Intent(Intent.ACTION_PICK,
          Media.EXTERNAL_CONTENT_URI);
      startActivityForResult(choosePictureIntent, 0);
    } else
    {
      if (alteredBitmap != null)
      {
        try
        {
          Uri ImageFileUri = getContentResolver().insert(
              Media.EXTERNAL_CONTENT_URI, new ContentValues());
          OutputStream imageFileOS = getContentResolver()
              .openOutputStream(ImageFileUri);
          alteredBitmap.compress(CompressFormat.JPEG, 100,
              imageFileOS);
          Toast.makeText(this, "Saved! ", Toast.LENGTH_LONG).show();
        } catch (FileNotFoundException e)
        {
          // TODO Auto-generated catch block
          e.printStackTrace();
        }
      }
    }
  }
  @Override
  protected void onActivityResult(int requestCode, int resultCode, Intent data)
  {
    // TODO Auto-generated method stub
    super.onActivityResult(requestCode, resultCode, data);
    if (resultCode == RESULT_OK)
    {
      savePicture.setVisibility(View.VISIBLE);
      Uri imageFileUri = data.getData();
      Display currentDisplay = getWindowManager().getDefaultDisplay();
      @SuppressWarnings("deprecation")
      float dw = currentDisplay.getWidth();
      @SuppressWarnings("deprecation")
      float dh = currentDisplay.getHeight();
      BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
      bmpFactoryOptions.inJustDecodeBounds = true;
      try
      {
        bitmap = BitmapFactory
            .decodeStream(
                getContentResolver().openInputStream(
                    imageFileUri), null, bmpFactoryOptions);
      } catch (FileNotFoundException e)
      {
        // TODO Auto-generated catch block
        e.printStackTrace();
      }
      int heightRatio = (int) Math.ceil(bmpFactoryOptions.outHeight / dh);
      int widthRatio = (int) Math.ceil(bmpFactoryOptions.outWidth / dw);
      if (heightRatio >= 1 && widthRatio >= 1)
      {
        if (heightRatio > widthRatio)
        {
          bmpFactoryOptions.inSampleSize = heightRatio;
          // Log.e(TAG,"heightRatio");
        } else
        {
          bmpFactoryOptions.inSampleSize = widthRatio;
          // Log.e(TAG,"widthRatio");
        }
      }
      // Log.e(TAG,"heightRatio:"+heightRatio+" widthRatio:"+widthRatio);
      bmpFactoryOptions.inJustDecodeBounds = false;
      try
      {
        bitmap = BitmapFactory
            .decodeStream(
                getContentResolver().openInputStream(
                    imageFileUri), null, bmpFactoryOptions);
      } catch (FileNotFoundException e)
      {
        // TODO Auto-generated catch block
        e.printStackTrace();
      }
      alteredBitmap = Bitmap.createBitmap(bitmap.getWidth(),
          bitmap.getHeight(), bitmap.getConfig());
      Log.e(TAG, "bitmap.Height:" + bitmap.getHeight());
      canvas = new Canvas(alteredBitmap);
      paint = new Paint();
      paint.setColor(Color.GREEN);
      paint.setStrokeWidth(5);
      matrix = new Matrix();
      canvas.drawBitmap(bitmap, matrix, paint);
      imageView.setImageBitmap(alteredBitmap);
      // top=imageView.getTop(); //144.0
      // bottom=imageView.getBottom();//144.0
      // height=imageView.getHeight(); //0.0
      // Log.e(TAG, "bottom:"+bottom);
      imageView.setOnTouchListener(this);
    }
  }
}