android 实现在照片上绘制涂鸦的方法

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:layout_margin="5dp"
 android:orientation="vertical">

 <ImageView
  android:id="@+id/iv_draw_pic"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:layout_gravity="center_horizontal"
  android:layout_margin="10dp" />

 <RelativeLayout
  android:layout_width="match_parent"
  android:layout_height="wrap_content">

  <Button
   android:id="@+id/btn_choose"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_margin="5dp"
   android:layout_weight="1"
   android:text="选择照片" />

  <Button
   android:id="@+id/btn_save"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_alignParentRight="true"
   android:layout_margin="5dp"
   android:layout_weight="1"
   android:text="保存照片" />

  <Button
   android:id="@+id/btn_clear"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_alignParentBottom="true"
   android:layout_centerHorizontal="true"
   android:layout_margin="5dp"
   android:layout_weight="1"
   android:text="擦除笔迹" />
 </RelativeLayout>

</FrameLayout>

  switch (model){
   case "MI 4LTE":
    scale = 1.1f;
    break;
   case "HUAWEI NXT-AL10":
    scale = 1.5f;
    break;
  }

 @Override
 public boolean onTouch(View view, MotionEvent motionEvent) {
  int action = motionEvent.getAction();
  switch (action) {
   case MotionEvent.ACTION_CANCEL:
    break;
   case MotionEvent.ACTION_DOWN:
    downX = motionEvent.getX() * scale;
    downY = motionEvent.getY() * scale;
    break;
   case MotionEvent.ACTION_UP:
    upX = motionEvent.getX() * scale;
    upY = motionEvent.getY() * scale;
    canvas.drawLine(downX, downY, upX, upY, paint);
    iv_drawpicture.invalidate();
    break;
   case MotionEvent.ACTION_MOVE:
    upX = motionEvent.getX() * scale;
    upY = motionEvent.getY() * scale;
    canvas.drawLine(downX, downY, upX, upY, paint);
    iv_drawpicture.invalidate();
    downX = upX;
    downY = upY;
    break;
   default:
    break;
  }
  return true;
 }

try {

  Uri imageUri = getContentResolver().insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, new ContentValues());
  OutputStream os = getContentResolver().openOutputStream(imageUri);

  //compress方法将图片转换成JPG或者PNG格式
  drawBitmap.compress(Bitmap.CompressFormat.JPEG, 90, os);
  Toast.makeText(this, "Saved：" + imageUri.toString(), Toast.LENGTH_LONG).show();
 } catch (FileNotFoundException e) {
  e.printStackTrace();
 }

 drawBitmap = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());
 canvas = createCanvas(drawBitmap);
 paint = createPaint();
 canvas.drawBitmap(bmp, 0, 0, paint);
 iv_drawpicture.setImageBitmap(drawBitmap);
 iv_drawpicture.setOnTouchListener(this);