Merge pull request #217 from SixLabors/sw/parse-svg-path

Parse Svg Path

Author: JimBobSquarePants

src/ImageSharp.Drawing/Shapes/Path.cs

@@ -116,5 +116,268 @@ SegmentInfo IPathInternals.PointAlongPath(float distance)
 
         /// <inheritdoc/>
         IReadOnlyList<InternalPath> IInternalPathOwner.GetRingsAsInternalPath() => new[] { this.InnerPath };
+
+        /// <summary>
+        /// Converts an SVG path string into an <see cref="IPath"/>.
+        /// </summary>
+        /// <param name="svgPath">The string containing the SVG path data.</param>
+        /// <param name="value">
+        /// When this method returns, contains the logic path converted from the given SVG path string; otherwise, <see langword="null"/>.
+        /// This parameter is passed uninitialized.
+        /// </param>
+        /// <returns><see langword="true"/> if the input value can be parsed and converted; otherwise, <see langword="false"/>.</returns>
+        public static bool TryParseSvgPath(string svgPath, out IPath value)
+            => TryParseSvgPath(svgPath.AsSpan(), out value);
+
+        /// <summary>
+        /// Converts an SVG path string into an <see cref="IPath"/>.
+        /// </summary>
+        /// <param name="svgPath">The string containing the SVG path data.</param>
+        /// <param name="value">
+        /// When this method returns, contains the logic path converted from the given SVG path string; otherwise, <see langword="null"/>.
+        /// This parameter is passed uninitialized.
+        /// </param>
+        /// <returns><see langword="true"/> if the input value can be parsed and converted; otherwise, <see langword="false"/>.</returns>
+        public static bool TryParseSvgPath(ReadOnlySpan<char> svgPath, out IPath value)
+        {
+            value = null;
+
+            var builder = new PathBuilder();
+
+            PointF first = PointF.Empty;
+            PointF c = PointF.Empty;
+            PointF lastc = PointF.Empty;
+            PointF point1;
+            PointF point2;
+            PointF point3;
+
+            char op = '\0';
+            char previousOp = '\0';
+            bool relative = false;
+            while (true)
+            {
+                svgPath = svgPath.TrimStart();
+                if (svgPath.Length == 0)
+                {
+                    break;
+                }
+
+                char ch = svgPath[0];
+                if (char.IsDigit(ch) || ch == '-' || ch == '+' || ch == '.')
+                {
+                    // Are we are the end of the string or we are at the end of the path?
+                    if (svgPath.Length == 0 || op == 'Z')
+                    {
+                        return false;
+                    }
+                }
+                else if (IsSeparator(ch))
+                {
+                    svgPath = TrimSeparator(svgPath);
+                }
+                else
+                {
+                    op = ch;
+                    relative = false;
+                    if (char.IsLower(op))
+                    {
+                        op = char.ToUpper(op);
+                        relative = true;
+                    }
+
+                    svgPath = TrimSeparator(svgPath.Slice(1));
+                }
+
+                switch (op)
+                {
+                    case 'M':
+                        svgPath = FindPoint(svgPath, out point1, relative, c);
+                        builder.MoveTo(point1);
+                        previousOp = '\0';
+                        op = 'L';
+                        c = point1;
+                        break;
+                    case 'L':
+                        svgPath = FindPoint(svgPath, out point1, relative, c);
+                        builder.LineTo(point1);
+                        c = point1;
+                        break;
+                    case 'H':
+                        svgPath = FindScaler(svgPath, out float x);
+                        if (relative)
+                        {
+                            x += c.X;
+                        }
+
+                        builder.LineTo(x, c.Y);
+                        c.X = x;
+                        break;
+                    case 'V':
+                        svgPath = FindScaler(svgPath, out float y);
+                        if (relative)
+                        {
+                            y += c.Y;
+                        }
+
+                        builder.LineTo(c.X, y);
+                        c.Y = y;
+                        break;
+                    case 'C':
+                        svgPath = FindPoint(svgPath, out point1, relative, c);
+                        svgPath = FindPoint(svgPath, out point2, relative, c);
+                        svgPath = FindPoint(svgPath, out point3, relative, c);
+                        builder.CubicBezierTo(point1, point2, point3);
+                        lastc = point2;
+                        c = point3;
+                        break;
+                    case 'S':
+                        svgPath = FindPoint(svgPath, out point2, relative, c);
+                        svgPath = FindPoint(svgPath, out point3, relative, c);
+                        point1 = c;
+                        if (previousOp is 'C' or 'S')
+                        {
+                            point1.X -= lastc.X - c.X;
+                            point1.Y -= lastc.Y - c.Y;
+                        }
+
+                        builder.CubicBezierTo(point1, point2, point3);
+                        lastc = point2;
+                        c = point3;
+                        break;
+                    case 'Q': // Quadratic Bezier Curve
+                        svgPath = FindPoint(svgPath, out point1, relative, c);
+                        svgPath = FindPoint(svgPath, out point2, relative, c);
+                        builder.QuadraticBezierTo(point1, point2);
+                        lastc = point1;
+                        c = point2;
+                        break;
+                    case 'T':
+                        svgPath = FindPoint(svgPath, out point2, relative, c);
+                        point1 = c;
+                        if (previousOp is 'Q' or 'T')
+                        {
+                            point1.X -= lastc.X - c.X;
+                            point1.Y -= lastc.Y - c.Y;
+                        }
+
+                        builder.QuadraticBezierTo(point1, point2);
+                        lastc = point1;
+                        c = point2;
+                        break;
+                    case 'A':
+                        svgPath = FindScaler(svgPath, out float radiiX);
+                        svgPath = TrimSeparator(svgPath);
+                        svgPath = FindScaler(svgPath, out float radiiY);
+                        svgPath = TrimSeparator(svgPath);
+                        svgPath = FindScaler(svgPath, out float angle);
+                        svgPath = TrimSeparator(svgPath);
+                        svgPath = FindScaler(svgPath, out float largeArc);
+                        svgPath = TrimSeparator(svgPath);
+                        svgPath = FindScaler(svgPath, out float sweep);
+
+                        svgPath = FindPoint(svgPath, out PointF point, relative, c);
+                        if (svgPath.Length > 0)
+                        {
+                            builder.ArcTo(radiiX, radiiY, angle, largeArc == 1, sweep == 1, point);
+                            c = point;
+                        }
+
+                        break;
+                    case 'Z':
+                        builder.CloseFigure();
+                        c = first;
+                        break;
+                    case '~':
+                        svgPath = FindPoint(svgPath, out point1, relative, c);
+                        svgPath = FindPoint(svgPath, out point2, relative, c);
+                        builder.MoveTo(point1);
+                        builder.LineTo(point2);
+                        break;
+                    default:
+                        return false;
+                }
+
+                if (previousOp == 0)
+                {
+                    first = c;
+                }
+
+                previousOp = op;
+            }
+
+            value = builder.Build();
+            return true;
+
+            static bool IsSeparator(char ch)
+                => char.IsWhiteSpace(ch) || ch == ',';
+
+            static ReadOnlySpan<char> TrimSeparator(ReadOnlySpan<char> data)
+            {
+                if (data.Length == 0)
+                {
+                    return data;
+                }
+
+                int idx = 0;
+                for (; idx < data.Length; idx++)
+                {
+                    if (!IsSeparator(data[idx]))
+                    {
+                        break;
+                    }
+                }
+
+                return data.Slice(idx);
+            }
+
+            static ReadOnlySpan<char> FindPoint(ReadOnlySpan<char> str, out PointF value, bool isRelative, PointF relative)
+            {
+                str = FindScaler(str, out float x);
+                str = FindScaler(str, out float y);
+                if (isRelative)
+                {
+                    x += relative.X;
+                    y += relative.Y;
+                }
+
+                value = new PointF(x, y);
+                return str;
+            }
+
+            static ReadOnlySpan<char> FindScaler(ReadOnlySpan<char> str, out float scaler)
+            {
+                str = TrimSeparator(str);
+                scaler = 0;
+
+                for (int i = 0; i < str.Length; i++)
+                {
+                    if (IsSeparator(str[i]) || i == str.Length)
+                    {
+                        scaler = ParseFloat(str.Slice(0, i));
+                        return str.Slice(i);
+                    }
+                }
+
+                if (str.Length > 0)
+                {
+                    scaler = ParseFloat(str);
+                }
+
+                return ReadOnlySpan<char>.Empty;
+            }
+
+#if !NETCOREAPP2_1_OR_GREATER
+            static unsafe float ParseFloat(ReadOnlySpan<char> str)
+            {
+                fixed (char* p = str)
+                {
+                    return float.Parse(new string(p, 0, str.Length));
+                }
+            }
+#else
+            static float ParseFloat(ReadOnlySpan<char> str)
+                => float.Parse(str);
+#endif
+        }
     }
 }

src/ImageSharp.Drawing/Shapes/PathBuilder.cs

@@ -108,6 +108,15 @@ public PathBuilder MoveTo(PointF point)
         public PathBuilder LineTo(PointF point)
             => this.AddLine(this.currentPoint, point);
 
+        /// <summary>
+        /// Draws the line connecting the current the current point to the new point.
+        /// </summary>
+        /// <param name="x">The x.</param>
+        /// <param name="y">The y.</param>
+        /// <returns>The <see cref="PathBuilder"/></returns>
+        public PathBuilder LineTo(float x, float y)
+            => this.LineTo(new PointF(x, y));
+
         /// <summary>
         /// Adds the line connecting the current point to the new point.
         /// </summary>

tests/ImageSharp.Drawing.Tests/Drawing/FillPathTests.cs

@@ -23,31 +23,31 @@ public void FillPathSVGArcs<TPixel>(TestImageProvider<TPixel> provider)
             pb.MoveTo(new Vector2(80, 80))
               .ArcTo(45, 45, 0, false, false, new Vector2(125, 125))
               .LineTo(new Vector2(125, 80))
-              .LineTo(new Vector2(80, 80));
+              .CloseFigure();
 
             IPath path = pb.Build();
 
             pb = new PathBuilder();
             pb.MoveTo(new Vector2(230, 80))
               .ArcTo(45, 45, 0, true, false, new Vector2(275, 125))
               .LineTo(new Vector2(275, 80))
-              .LineTo(new Vector2(230, 80));
+              .CloseFigure();
 
             IPath path2 = pb.Build();
 
             pb = new PathBuilder();
             pb.MoveTo(new Vector2(80, 230))
               .ArcTo(45, 45, 0, false, true, new Vector2(125, 275))
               .LineTo(new Vector2(125, 230))
-              .LineTo(new Vector2(80, 230));
+              .CloseFigure();
 
             IPath path3 = pb.Build();
 
             pb = new PathBuilder();
             pb.MoveTo(new Vector2(230, 230))
               .ArcTo(45, 45, 0, true, true, new Vector2(275, 275))
               .LineTo(new Vector2(275, 230))
-              .LineTo(new Vector2(230, 230));
+              .CloseFigure();
 
             IPath path4 = pb.Build();
 

tests/ImageSharp.Drawing.Tests/Shapes/SvgPath.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using SixLabors.ImageSharp.Drawing.Processing;
+using SixLabors.ImageSharp.Drawing.Tests.TestUtilities.ImageComparison;
+using SixLabors.ImageSharp.PixelFormats;
+using Xunit;
+
+namespace SixLabors.ImageSharp.Drawing.Tests.Shapes
+{
+    public class SvgPath
+    {
+        [Theory]
+        [WithBlankImage(110, 70, PixelTypes.Rgba32, "M20,30 L40,5 L60,30 L80, 55 L100, 30", "zag")]
+        [WithBlankImage(110, 50, PixelTypes.Rgba32, "M20,30 Q40,5 60,30 T100,30", "wave")]
+        [WithBlankImage(500, 400, PixelTypes.Rgba32, @"M10,350 l 50,-25 a25,25 -30 0,1 50,-25 l 50,-25 a25,50 -30 0,1 50,-25 l 50,-25 a25,75 -30 0,1 50,-25 l 50,-25 a25,100 -30 0,1 50,-25 l 50,-25", "bumpy")]
+        [WithBlankImage(500, 400, PixelTypes.Rgba32, @"M300,200 h-150 a150,150 0 1,0 150,-150 z", "pie_small")]
+        [WithBlankImage(500, 400, PixelTypes.Rgba32, @"M275,175 v-150 a150,150 0 0,0 -150,150 z", "pie_big")]
+        [WithBlankImage(100, 100, PixelTypes.Rgba32, @"M50,50 L50,20 L80,50 z M40,60 L40,90 L10,60 z", "arrows")]
+        [WithBlankImage(500, 400, PixelTypes.Rgba32, @"M 10 315 L 110 215 A 30 50 0 0 1 162.55 162.45 L 172.55 152.45 A 30 50 -45 0 1 215.1 109.9 L 315 10", "chopped_oval")]
+        public void RenderSvgPath<TPixel>(TestImageProvider<TPixel> provider, string svgPath, string exampleImageKey)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            var parsed = Path.TryParseSvgPath(svgPath, out var path);
+            Assert.True(parsed);
+
+            provider.RunValidatingProcessorTest(
+                c => c.Fill(Color.White).Draw(Color.Red, 5, path),
+                new { type = exampleImageKey },
+                comparer: ImageComparer.TolerantPercentage(0.002f));
+        }
+    }
+}