c# - 在 2D 图形窗格上缩放信号

Question

我正在挠头想办法在 2D 图形窗格上缩放信号。故事是：我将我的应用程序连接到微控制器，并以固定的时间间隔读取数据值（电压点）。现在我想在我的图形窗格上绘制它。例子：

所以在图片中你在时间 0 看到的电压也是 0，这样继续下去，在 6 个数据点之后，我将清除窗格并重做整个工作。

问题是，我如何将这个电压转换为像素值，记住我希望图形窗格的中间是我的信号 0，就像正常的笛卡尔图一样。有人可以帮我弄清楚这种情况下的缩放算法吗？

Answer 1

看起来像简单的数学：只需将 width/2 添加到您传递给绘图函数的所有 X 坐标中。假设您有一个包含 6 个点的数组，您可以执行以下操作：

var g = this.CreateGraphics();
var points = new Point[6]{new Point(0, 0), new Point(10, 10), new Point(30, 0), new Point(40,20), new Point(50, 0), new Point(60,30)};
for (int i = 0; i < points.Length-1; i++)
{
    g.DrawLine(Pens.Black, points[i].X + Width / 2, Height / 2 - points[i].Y, points[i + 1].X + Width / 2, Height / 2 - points[i + 1].Y);
}

或者，您可以调用TranslateTransform函数将所有进一步的绘图移动到 X 和 Y 轴的某个量。例子：

var g = this.CreateGraphics();
var points = new Point[6]{new Point(0, 0), new Point(10, 10), new Point(30, 0), new Point(40,20), new Point(50, 0), new Point(60,30)};
g.TranslateTransform(Width / 2, 0, System.Drawing.Drawing2D.MatrixOrder.Append);
for (int i = 0; i < points.Length-1; i++)
{
    g.DrawLine(Pens.Black, points[i].X, Height / 2 - points[i].Y, points[i + 1].X, Height / 2 - points[i + 1].Y);
}

Answer 2

也许这会很有用（记住 scale 和 translate 函数正在改变数组中的点）：

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
    var points = new PointF[6] { new PointF(0, 0), new PointF(30, 3), new PointF(90, 0), new PointF(190, 3.1f), new PointF(270, -0.5f), new PointF(360, 3.5f) };

    float maxX = (from p in points select p).Max(t => t.X);
    float maxY = (from p in points select p).Max(t => t.Y);            

    float xSizeToFit = pictureBox1.Width;
    float ySizeToFit = pictureBox1.Height/2;
    float scaleX = xSizeToFit / maxX;
    float scaleY = ySizeToFit / maxY;

    // scale to fit to given size
    ScalePoints(points, scaleX, scaleY);
    // translate to center
    TranslatePoints(points, this.pictureBox1.Width / 2 - 0.5f * xSizeToFit, this.pictureBox1.Height / 2 + 0.5f * ySizeToFit);

    DrawAxis(e.Graphics, this.pictureBox1.Size);
    e.Graphics.DrawLines(Pens.Black, points);                
}

private void TranslatePoints(PointF[] points, float transX, float transY)
{
    for (int i = 0; i < points.Length; i++)
    {
        points[i].X += transX;
        points[i].Y = transY - points[i].Y;
    }
}

private void ScalePoints(PointF[] points, float scaleX, float scaleY)
{
    for (int i = 0; i < points.Length; i++)
    {
        points[i].X *= scaleX;
        points[i].Y *= scaleY;
    }
}

public void DrawAxis(Graphics g, Size size)
{
    //x
    g.DrawLine(Pens.Black, 0, size.Height / 2, size.Width, size.Height / 2);
    //y
    g.DrawLine(Pens.Black, size.Width / 2, size.Height, size.Width / 2, 0);           
}

private void pictureBox1_Resize(object sender, EventArgs e)
{
    pictureBox1.Invalidate();
}