Handle relative image hrefs without base URI

src/Svg.Model/Services/SvgService.cs

@@ -440,7 +440,7 @@
             return true;
         }
 
         return element.CustomAttributes.TryGetValue($"{SvgNamespaces.XmlNamespace}:base", out value);
     }
 
     internal static Uri GetImageDocumentUri(Uri uri)
@@ -488,6 +488,11 @@
                 return GetImageFromDataUri(uriString, svgOwnerElement, assetLoader);
             }
 
+            if (!uri.IsAbsoluteUri)
+            {
+                return default;
+            }
+
             return GetImageFromWeb(uri, assetLoader);
         }
         catch (Exception ex)

tests/Svg.Model.UnitTests/SvgServiceImageUriTests.cs

@@ -0,0 +1,84 @@
+using System;
+using Svg;
+using Svg.Model.Services;
+using Xunit;
+
+namespace Svg.Model.UnitTests;
+
+public class SvgServiceImageUriTests
+{
+    [Fact]
+    public void GetImageUri_RelativeImageHrefWithoutBaseUri_RemainsRelative()
+    {
+        const string svg = """
+            <svg xmlns="http://www.w3.org/2000/svg"
+                 xmlns:xlink="http://www.w3.org/1999/xlink"
+                 width="32" height="32">
+              <image id="missing-image" width="99" height="108" xlink:href="6F03BD87.png" />
+            </svg>
+            """;
+
+        var document = SvgService.FromSvg(svg);
+        Assert.NotNull(document);
+
+        var image = Assert.IsType<SvgImage>(document!.GetElementById("missing-image"));
+
+        var uri = SvgService.GetImageUri(image.Href, image);
+
+        Assert.False(uri.IsAbsoluteUri);
+        Assert.Equal("6F03BD87.png", uri.OriginalString);
+    }
+
+    [Fact]
+    public void GetImage_RelativeImageHrefWithoutBaseUri_ReturnsNull()
+    {
+        const string svg = """
+            <svg xmlns="http://www.w3.org/2000/svg"
+                 xmlns:xlink="http://www.w3.org/1999/xlink"
+                 width="32" height="32">
+              <image id="missing-image" width="99" height="108" xlink:href="6F03BD87.png" />
+            </svg>
+            """;
+
+        var document = SvgService.FromSvg(svg);
+        Assert.NotNull(document);
+
+        var image = Assert.IsType<SvgImage>(document!.GetElementById("missing-image"));
+
+        var loadedImage = SvgService.GetImage(image.Href, image, new TestAssetLoader());
+
+        Assert.Null(loadedImage);
+    }
+
+    [Fact]
+    public void GetImageUri_DocumentOwnerWithoutBaseUri_RemainsRelative()
+    {
+        const string svg = """
+            <svg xmlns="http://www.w3.org/2000/svg" width="32" height="32" />
+            """;
+
+        var document = SvgService.FromSvg(svg);
+        Assert.NotNull(document);
+
+        var uri = SvgService.GetImageUri("6F03BD87.png", document!);
+
+        Assert.False(uri.IsAbsoluteUri);
+        Assert.Equal("6F03BD87.png", uri.OriginalString);
+    }
+
+    [Fact]
+    public void GetImageUri_DocumentOwnerUsesDocumentBaseUri()
+    {
+        const string svg = """
+            <svg xmlns="http://www.w3.org/2000/svg" width="32" height="32" />
+            """;
+
+        var document = SvgService.FromSvg(svg);
+        Assert.NotNull(document);
+        document!.BaseUri = new Uri("https://example.test/assets/source.svg");
+
+        var uri = SvgService.GetImageUri("6F03BD87.png", document);
+
+        Assert.Equal(new Uri("https://example.test/assets/6F03BD87.png"), uri);
+    }
+}

tests/Svg.Skia.UnitTests/SKSvgTests.cs

@@ -188,4 +188,35 @@ public void Load_CssFontFaceWithExternalFontUrl_DoesNotCrash()
         Assert.Equal(120, image.Width);
         Assert.Equal(40, image.Height);
     }
+
+    [Fact]
+    public void Load_RelativeImageHrefWithoutBaseUri_SkipsMissingImage()
+    {
+        const string svgMarkup = """
+            <svg xmlns="http://www.w3.org/2000/svg"
+                 xmlns:xlink="http://www.w3.org/1999/xlink"
+                 width="32px" height="32px" viewBox="0 0 32 32">
+              <rect width="32" height="32" fill="#232B34" />
+              <g opacity="0.1">
+                <image width="99" height="108" xlink:href="6F03BD87.png"
+                       transform="matrix(1 0 0 1 -33.5 -44.6934)" />
+              </g>
+              <circle cx="16" cy="16" r="8" fill="#586871" />
+            </svg>
+            """;
+
+        var svg = new SKSvg();
+        using var input = new MemoryStream(Encoding.UTF8.GetBytes(svgMarkup));
+        using var _ = svg.Load(input);
+        using var output = new MemoryStream();
+
+        Assert.True(svg.Save(output, SkiaSharp.SKColors.Transparent));
+
+        output.Position = 0;
+        using var image = Image.Load<Rgba32>(output);
+        Assert.Equal(32, image.Width);
+        Assert.Equal(32, image.Height);
+        Assert.Equal(new Rgba32(0x23, 0x2B, 0x34), image[0, 0]);
+        Assert.Equal(new Rgba32(0x58, 0x68, 0x71), image[16, 16]);
+    }
 }