更改画布的大小和在屏幕上的位置

Question

我正在创建一个用于手写数字识别的应用程序。在这种情况下，我需要一个正方形大小的画布，稍后将其转换为可接受的格式以供实现。我的问题是我无法按比例缩小画布，就像可以使用javascript一样。位图被缩放为正方形，并且图形仅保存在位图上，但是当我触摸屏幕时，手指的路径显示在位图区域之外。

我认为用一些图像显示我的问题会更好：

所需的画布大小和屏幕上的位置（大约）：

位图位置（在左方为正方形）和位图外部的路径跟踪（触摸屏幕时）：

以下是我停止触摸屏幕的屏幕截图：

我尝试了很多事情，例如嵌套布局，更改位图大小，甚至创建自己的视图并更改其尺寸-这些都不起作用。有没有人建议如何做？

以下是DrawingView的代码：

public class DrawingView extends View {

    public int width;
    public  int height;
    private Bitmap mBitmap;
    private Canvas mCanvas;
    private Path mPath;
    private Paint   mBitmapPaint;
    Context context;
    private Paint circlePaint;
    private Path circlePath;

    public DrawingView(Context c) {
        this(c, null);
    }

    public DrawingView(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.context=context;
        mPath = new Path();
        mBitmapPaint = new Paint(Paint.DITHER_FLAG);
        circlePaint = new Paint();
        circlePath = new Path();
        circlePaint.setAntiAlias(true);
        circlePaint.setColor(Color.BLUE);
        circlePaint.setStyle(Paint.Style.STROKE);
        circlePaint.setStrokeJoin(Paint.Join.MITER);
        circlePaint.setStrokeWidth(4f);
    }


    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);

        mBitmap = Bitmap.createBitmap(600, 600, Bitmap.Config.ARGB_8888);
        mCanvas = new Canvas(mBitmap);

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        canvas.drawBitmap( mBitmap, 0, 0, mBitmapPaint);
        canvas.drawPath( mPath,  mPaint);
        canvas.drawPath( circlePath,  circlePaint);
    }

    private float mX, mY;
    private static final float TOUCH_TOLERANCE = 4;

    private void touch_start(float x, float y) {
        mPath.reset();
        mPath.moveTo(x, y);
        mX = x;
        mY = y;
    }

    private void touch_move(float x, float y) {
        float dx = Math.abs(x - mX);
        float dy = Math.abs(y - mY);
        if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
            mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
            mX = x;
            mY = y;

            circlePath.reset();
            circlePath.addCircle(mX, mY, 30, Path.Direction.CW);
        }
    }

    private void touch_up() {
        mPath.lineTo(mX, mY);
        circlePath.reset();
        // commit the path to our offscreen
        mCanvas.drawPath(mPath,  mPaint);
        // kill this so we don't double draw
        mPath.reset();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float x = event.getX();
        float y = event.getY();

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                touch_start(x, y);
                invalidate();
                break;
            case MotionEvent.ACTION_MOVE:
                touch_move(x, y);
                invalidate();
                break;
            case MotionEvent.ACTION_UP:
                touch_up();
                invalidate();
                break;
        }
        return true;
    }
}