Equivalent of glOrtho in WPF

c#, wpf, xaml

Solution

I created an extension method on Canvas that allows you to set a Cartesian coordinate system. An example invocation is:

canvas.SetCoordinateSystem(-10, 10, -10, 10)

That will set the coordinate system of `canvas` so that x goes from -10 to 10 and y goes from -10 to 10.

Here's the extension method:

public static Canvas SetCoordinateSystem(this Canvas canvas, Double xMin, Double xMax, Double yMin, Double yMax)
{
    var width = xMax - xMin;
    var height = yMax - yMin;

    var translateX = -xMin;
    var translateY = height + yMin;

    var group = new TransformGroup();

    group.Children.Add(new TranslateTransform(translateX, -translateY));
    group.Children.Add(new ScaleTransform(canvas.ActualWidth / width, canvas.ActualHeight / -height));

    canvas.RenderTransform = group;

    return canvas;
}

Here's a demo program which plots Sin(x) on a canvas along with the X and Y axes:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace CanvasScale
{
    public static class CanvasUtils
    {
        public static Canvas SetCoordinateSystem(this Canvas canvas, Double xMin, Double xMax, Double yMin, Double yMax)
        {
            var width = xMax - xMin;
            var height = yMax - yMin;

            var translateX = -xMin;
            var translateY = height + yMin;

            var group = new TransformGroup();

            group.Children.Add(new TranslateTransform(translateX, -translateY));
            group.Children.Add(new ScaleTransform(canvas.ActualWidth / width, canvas.ActualHeight / -height));

            canvas.RenderTransform = group;

            return canvas;
        }
    }

    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            var canvas = new Canvas();

            Content = canvas;

            SizeChanged += (s, e) => canvas.SetCoordinateSystem(-10, 10, -10, 10);                

            canvas.Children.Add(new Line() { X1 = -10, Y1 = 0, X2 = 10, Y2 = 0, Stroke = Brushes.Black, StrokeThickness = 0.2 });
            canvas.Children.Add(new Line() { X1 = 0, Y1 = -10, X2 = 0, Y2 = 10, Stroke = Brushes.Black, StrokeThickness = 0.2 });

            var polyline = new Polyline()
            {
                Stroke = Brushes.BurlyWood,
                StrokeThickness = 0.1,
                Points = new PointCollection()
            };

            for (var x = -10.0; x <= 10.0; x += 0.1)
                polyline.Points.Add(new Point(x, Math.Sin(x)));

            canvas.Children.Add(polyline);
        }
    }
}

Here's what it looks like:

Problem

In OpenGL I can do this: ``` glOrtho(-10, 10, -10, 10, -1, 1) ``` to establish a coordinate system where x ranges from -10 to 10 and y ranges from -10 to 10. Is there a way to change the coordinate system of a canvas in WPF?

Original source

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