Add canvas and image support

Adds support for drawing "pixels" and displaying
images in the terminal.

examples/Canvas/Canvas.csproj

@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <IsPackable>false</IsPackable>
+    <Title>Canvas</Title>
+    <Description>Demonstrates how to render pixels and images.</Description>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\Spectre.Console.ImageSharp\Spectre.Console.ImageSharp.csproj" />
+    <ProjectReference Include="..\..\src\Spectre.Console\Spectre.Console.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <None Update="cake.png">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+  </ItemGroup>
+
+</Project>

examples/Canvas/Mandelbrot.cs

@@ -0,0 +1,87 @@
+/*
+Ported from: https://rosettacode.org/wiki/Mandelbrot_set#C.23
+Licensed under GNU Free Documentation License 1.2
+*/
+
+using System;
+using Spectre.Console;
+
+namespace CanvasExample
+{
+    public static class Mandelbrot
+    {
+        private const double MaxValueExtent = 2.0;
+
+        private struct ComplexNumber
+        {
+            public double Real { get; }
+            public double Imaginary { get; }
+
+            public ComplexNumber(double real, double imaginary)
+            {
+                Real = real;
+                Imaginary = imaginary;
+            }
+
+            public static ComplexNumber operator +(ComplexNumber x, ComplexNumber y)
+            {
+                return new ComplexNumber(x.Real + y.Real, x.Imaginary + y.Imaginary);
+            }
+
+            public static ComplexNumber operator *(ComplexNumber x, ComplexNumber y)
+            {
+                return new ComplexNumber(x.Real * y.Real - x.Imaginary * y.Imaginary,
+                    x.Real * y.Imaginary + x.Imaginary * y.Real);
+            }
+
+            public double Abs()
+            {
+                return Real * Real + Imaginary * Imaginary;
+            }
+        }
+
+        public static Canvas Generate(int width, int height)
+        {
+            var canvas = new Canvas(width, height);
+
+            var scale = 2 * MaxValueExtent / Math.Min(canvas.Width, canvas.Height);
+            for (var i = 0; i < canvas.Height; i++)
+            {
+                var y = (canvas.Height / 2 - i) * scale;
+                for (var j = 0; j < canvas.Width; j++)
+                {
+                    var x = (j - canvas.Width / 2) * scale;
+                    var value = Calculate(new ComplexNumber(x, y));
+                    canvas.SetPixel(j, i, GetColor(value));
+                }
+            }
+
+            return canvas;
+        }
+
+        private static double Calculate(ComplexNumber c)
+        {
+            const int MaxIterations = 1000;
+            const double MaxNorm = MaxValueExtent * MaxValueExtent;
+
+            var iteration = 0;
+            var z = new ComplexNumber();
+            do
+            {
+                z = z * z + c;
+                iteration++;
+            } while (z.Abs() < MaxNorm && iteration < MaxIterations);
+
+            return iteration < MaxIterations
+                ? (double)iteration / MaxIterations
+                : 0;
+        }
+
+        private static Color GetColor(double value)
+        {
+            const double MaxColor = 256;
+            const double ContrastValue = 0.2;
+            return new Color(0, 0, (byte)(MaxColor * Math.Pow(value, ContrastValue)));
+        }
+    }
+}

examples/Canvas/Program.cs

@@ -0,0 +1,36 @@
+using SixLabors.ImageSharp.Processing;
+using Spectre.Console;
+using Spectre.Console.Rendering;
+
+namespace CanvasExample
+{
+    public static class Program
+    {
+        public static void Main()
+        {
+            // Draw a mandelbrot set using a Canvas
+            var mandelbrot = Mandelbrot.Generate(32, 32);
+            Render(mandelbrot, "Mandelbrot");
+
+            // Draw an image using CanvasImage powered by ImageSharp.
+            // This requires the "Spectre.Console.ImageSharp" NuGet package.
+            var image = new CanvasImage("cake.png");
+            image.BilinearResampler();
+            image.MaxWidth(16);
+            Render(image, "Image from file (16 wide)");
+
+            // Draw image again, but without render width
+            image.NoMaxWidth();
+            image.Mutate(ctx => ctx.Grayscale().Rotate(-45).EntropyCrop());
+            Render(image, "Image from file (fit, greyscale, rotated)");
+        }
+
+        private static void Render(IRenderable canvas, string title)
+        {
+            AnsiConsole.WriteLine();
+            AnsiConsole.Render(new Rule($"[yellow]{title}[/]").LeftAligned().RuleStyle("grey"));
+            AnsiConsole.WriteLine();
+            AnsiConsole.Render(canvas);
+        }
+    }
+}

examples/Rules/Program.cs

@@ -7,34 +7,34 @@ namespace EmojiExample
         public static void Main(string[] args)
         {
             // No title
-            WrapInPanel(
+            Render(
                 new Rule()
                     .RuleStyle(Style.Parse("yellow"))
                     .AsciiBorder()
                     .LeftAligned());
 
             // Left aligned title
-            WrapInPanel(
+            Render(
                 new Rule("[blue]Left aligned[/]")
                     .RuleStyle(Style.Parse("red"))
                     .DoubleBorder()
                     .LeftAligned());
 
             // Centered title
-            WrapInPanel(
+            Render(
                 new Rule("[green]Centered[/]")
                     .RuleStyle(Style.Parse("green"))
                     .HeavyBorder()
                     .Centered());
 
             // Right aligned title
-            WrapInPanel(
+            Render(
                 new Rule("[red]Right aligned[/]")
                     .RuleStyle(Style.Parse("blue"))
                     .RightAligned());
         }
 
-        private static void WrapInPanel(Rule rule)
+        private static void Render(Rule rule)
         {
             AnsiConsole.Render(rule);
             AnsiConsole.WriteLine();