Add SkiaSharp.Extended.Drawing.Common — cross-platform System.Drawing.Common replacement#388
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Add SkiaSharp.Extended.Drawing.Common — cross-platform System.Drawing.Common replacement#388mattleibow wants to merge 84 commits into
mattleibow wants to merge 84 commits into
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- Generated API stubs from System.Drawing.Common 10.0.2 (netstandard2.0) using Microsoft.DotNet.GenAPI.Tool - 3,041 lines covering 148 types across 6 namespaces - All method bodies throw PlatformNotSupportedException - Added Microsoft.DotNet.ApiCompat.Tool for CI validation - Added baseline assembly in tools/api-baseline/ Note: Generated stubs have compile errors that need fixing: - NullableAttribute/NullableContextAttribute removed (compiler-managed) - Missing interface implementations (ISerializable, ICollection) - Protected Finalize on sealed classes - DefaultMember attribute conflicts with indexers - SupportedOSPlatformAttribute missing on netstandard2.0 Co-authored-by: Copilot <[email protected]>
146 files across 6 namespace directories: - System/Drawing/ (43 files) - System/Drawing/Design/ (1 file) - System/Drawing/Drawing2D/ (36 files) - System/Drawing/Imaging/ (33 files) - System/Drawing/Printing/ (27 files) - System/Drawing/Text/ (6 files) Co-authored-by: Copilot <[email protected]>
Fixes applied to GenAPI-generated stubs: - Remove protected modifier from destructors (~ClassName) - Remove DefaultMemberAttribute on types with indexers - Add ISerializable.GetObjectData to Font, Icon, Image - Add IDisposable.Dispose to FontConverter.FontNameConverter - Add ICollection members to PrinterSettings collections - Remove RequiresUnreferencedCodeAttribute (netstandard2.0 compat) - Remove SupportedOSPlatformAttribute (netstandard2.0 compat) - Fix delegate signatures (DrawImageAbort, EnumerateMetafileProc, PlayRecordCallback, PrintEventHandler, PrintPageEventHandler, QueryPageSettingsEventHandler) - Add internal constructors to suppress public defaults on types with no visible constructors in baseline - Fix Image/FontCollection protected Dispose(bool) visibility - Set AssemblyVersion to 10.0.0.0 to match baseline ApiCompat result: PASS (only public key token suppressed) Co-authored-by: Copilot <[email protected]>
- Add api_compat job to azure-pipelines-public.yml that runs dotnet apicompat --strict-mode against the baseline assembly - Add dotnet-eng NuGet feed for GenAPI tool restore - Add README.md documenting the API baseline and update process Co-authored-by: Copilot <[email protected]>
- SkiaSharp.Drawing.Tests project with xUnit v3 - PixelCompatibilityTestBase with tolerance tiers, reference image comparison via SKPixelComparer, and diff visualization on failure - ApiSurfaceTests validating 16 core System.Drawing types exist with correct assembly name and PNSE behavior - All 18 tests pass Co-authored-by: Copilot <[email protected]>
- Add pixel_compat job to azure-pipelines-public.yml running SkiaSharp.Drawing.Tests with test result publishing - Add SkiaSharp.Drawing.Tests to solution file - Both api_compat and pixel_compat run after test job Co-authored-by: Copilot <[email protected]>
Image: - SKBitmap internal backing store - Width/Height/Size/PixelFormat properties - FromFile/FromStream static factories using SKBitmap.Decode - Save to file/stream with format detection - Clone, RotateFlip, GetThumbnailImage - Dispose pattern Bitmap: - All constructors (size, file, stream, copy, resize) - GetPixel/SetPixel via SKBitmap - SetResolution, MakeTransparent - Clone with sub-region extraction - LockBits/UnlockBits via pixel pointer Also: - Internal/SkiaConversions.cs for type mapping - ImageFormat/BitmapData/ColorPalette/FrameDimension backing - XML doc comments on all public members Co-authored-by: Copilot <[email protected]>
Brush: - Dispose pattern with tracking, internal CreatePaint() SolidBrush: - Color storage, SKPaint with Fill style Pen: - All properties (color, width, dash, caps, joins, miter) - CreatePaint() maps to SKPaint with Stroke style - LineCap/LineJoin/DashStyle → SKStrokeCap/SKStrokeJoin/SKPathEffect TextureBrush: - Image + WrapMode backing, SKShader.CreateBitmap Updated test to verify SolidBrush construction works. XML doc comments on all public members. Co-authored-by: Copilot <[email protected]>
Implemented via SKCanvas: - FromImage factory, Clear, Dispose, Flush - DrawLine (4 overloads), DrawLines, DrawRectangle (3), DrawRectangles, DrawEllipse (4), DrawArc (4), DrawPie (4), DrawPolygon (2) - FillRectangle (4), FillRectangles, FillEllipse (4), FillPie (3), FillPolygon (4) - DrawImage (11 overloads), DrawImageUnscaled (4) - TranslateTransform, ScaleTransform, RotateTransform, ResetTransform - Save/Restore state management - All state properties (SmoothingMode, InterpolationMode, etc.) PNSE retained for: Font/text, GraphicsPath, Region/clipping, Matrix, beziers, curves, metafiles, HDC/HWND XML doc comments on all 240+ public members. ApiCompat: PASS (zero breaking changes) Co-authored-by: Copilot <[email protected]>
Test coverage across 7 test files (2,484 lines): - BitmapTests (44): constructors, GetPixel/SetPixel, MakeTransparent, Clone, Save/Load roundtrips, LockBits, dispose - ImageTests (39): FromFile/FromStream, properties, Clone, RotateFlip, GetThumbnailImage, dispose - GraphicsTests (69): Clear, DrawLine/Rect/Ellipse/Arc/Pie/Polygon, FillRect/Ellipse/Pie/Polygon, DrawImage, transforms, Save/Restore - PenTests (32): constructors, all properties, DashStyle, caps, Clone - BrushTests (18): SolidBrush/TextureBrush construction, Clone, dispose - ImageFormatTests (22): all GUIDs, Equals, GetHashCode, ToString - SelfConsistencyTests (6): render→save→reload pixel comparison Also: - Fixed PixelCompatibilityTestBase.ConvertToSKBitmap to use internal backing - Added InternalsVisibleTo for test project access - ApiCompat: PASS Co-authored-by: Copilot <[email protected]>
Shared scenarios library (46 scenarios across 10 categories): - Clear, Lines, AA Lines, Rectangles, Ellipses, AA Ellipses, Arcs, Pies, Polygons, Composites, Colors Reference generator (Windows-only, net9.0-windows): - Uses real System.Drawing.Common (GDI+) to produce golden PNGs - tools/SkiaSharp.Drawing.ReferenceGenerator/ Pixel comparison tests: - SkiaDrawingSurface implements IDrawingSurface with our wrapper - ReferenceComparisonTests compares against golden images per-scenario - Gracefully skips when reference images absent (local dev) - 46 theory tests with category-based tolerance tiers CI pipeline: - generate_references job produces golden PNGs on Windows - pixel_compat job downloads and runs comparison tests Test results: 265 passed, 46 skipped (no ref images locally) ApiCompat: PASS Co-authored-by: Copilot <[email protected]>
Remove IDrawingSurface abstraction. Since SkiaSharp.Drawing uses the same System.Drawing namespace and API, the same source files compile against both backends via <Compile Include>. Shared scenarios (tools/SkiaSharp.Drawing.Scenarios/): - DrawingScenarios.cs — 46 scenarios using System.Drawing directly - ScenarioRunner.cs — Bitmap + Graphics.FromImage + Save Two consumers compile the same files: - ReferenceGenerator (net9.0-windows) → real System.Drawing/GDI+ - SkiaRunner + Tests (net10.0) → our SkiaSharp.Drawing wrapper Deleted: IDrawingSurface, TestScenario, Scenarios.csproj, SystemDrawingSurface, SkiaDrawingSurface All checks pass: build ✓, 311 tests ✓, ApiCompat ✓ Co-authored-by: Copilot <[email protected]>
Generated 46 reference images via SkiaRunner for all scenarios: Clear, Lines, AA Lines, Rectangles, Ellipses, AA Ellipses, Arcs, Pies, Polygons, Composites, Colors All 46 ReferenceComparisonTests now PASS with pixel comparison (previously skipped). These compare rendered output against checked-in baselines using SKPixelComparer. On Windows CI, the ReferenceGenerator will produce GDI+ golden images that replace these baselines for cross-backend validation. Test results: 311 passed, 0 skipped, 0 failed Co-authored-by: Copilot <[email protected]>
Co-authored-by: Copilot <[email protected]>
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Reference images generated by ReferenceGenerator on Windows CI (Build 157220) using real System.Drawing.Common/GDI+. Pixel comparison results against GDI+ (22 pass, 24 fail): - PASS: Clear (3), Lines (6), Rectangles (6), some Pies/Polygons/Composites - FAIL: Ellipses (1-4%), Arcs (0.8-2.1%), AA lines (1.8-2.4%), Polygons/Pies/Composites with curves (0.5-3.6%) Root causes of pixel differences: - Ellipse/arc rasterization differs between Skia and GDI+ - Anti-aliasing algorithms produce different edge pixels - Tolerances need tuning for curved geometry Co-authored-by: Copilot <[email protected]>
…arios - Always save 3 images per scenario: _actual, _reference, _diff - CI uploads as 'diff-images' artifact for download - Set TEST_ARTIFACTS_PATH env var in pixel_compat CI job - continueOnError on test step so artifacts always upload Co-authored-by: Copilot <[email protected]>
GDI+ treats integer coordinates with a +0.5 pixel center offset for curve rasterization (ellipses, arcs, pies). Without this, filled ellipses had 1-4% pixel error vs GDI+. With the fix, error drops to ~0.08%. Added GdiCurveRect() helper that applies +0.5 offset to all curve bounding rects in DrawEllipse, FillEllipse, DrawArc, DrawPie, FillPie. Also added 17 boundary precision test scenarios: - Even/odd ellipse sizes (4x4 through 80x80) - Stroke widths 1-3px on ellipses - Arc and pie at even/odd bounds - Rect-vs-ellipse overlay comparison 328 tests pass, ApiCompat clean. Co-authored-by: Copilot <[email protected]>
Same GDI+ pixel-center offset (+0.5) that fixed ellipses also applies to polygon vertices. Triangle stroke diff showed only the left diagonal edge differing — exactly the pattern expected from integer coordinate pixel-center vs pixel-edge addressing. Added GdiPolygonPath() helper that shifts all vertices by +0.5. Applied to DrawPolygon, FillPolygon, and FillPolygon(fillMode). Co-authored-by: Copilot <[email protected]>
- Removed continueOnError: true — test failures now fail CI - Added AA variants for Arcs (5), Pies (4), Polygons (6), Composites (3) — each curve scenario has both AA and non-AA - AA categories (LinesAA, EllipsesAA, ArcsAA, PiesAA, PolygonsAA, CompositesAA) use 5% tolerance - Non-AA categories use 0.5% tolerance - 346 tests, all passing Co-authored-by: Copilot <[email protected]>
Replaced 602-line DrawingScenarios.cs monolith with 16 category files + ScenarioBase. Each class = category folder, each method = scenario PNG. Adding a scenario is now: add a method, regenerate. Structure: tools/SkiaSharp.Drawing.Scenarios/ ├── ScenarioBase.cs (base class + AllScenarios registry) ├── Clear.cs, Lines.cs, LinesAA.cs, Rectangles.cs ├── Ellipses.cs, EllipsesAA.cs, Arcs.cs, ArcsAA.cs ├── Pies.cs, PiesAA.cs, Polygons.cs, PolygonsAA.cs ├── Composites.cs, CompositesAA.cs, Colors.cs, Boundaries.cs Also: - Deleted redundant SelfConsistencyTests - Updated .github/copilot-instructions.md with SkiaSharp.Drawing rules: implementation, test rules, tolerance tiers, how to add scenarios, build commands 340 tests pass, ApiCompat clean. Co-authored-by: Copilot <[email protected]>
Scenarios are now actual xUnit tests. No more custom runners.
dotnet test tools/ReferenceGenerator/ → GDI+ PNGs (Windows CI)
dotnet test tests/SkiaSharp.Drawing.Tests → runs 81 scenario tests
+ 259 unit tests
+ 81 reference comparisons
Changes:
- Added [Fact] to all 81 scenario methods across 16 category files
- ScenarioBase uses SCENARIO_OUTPUT_PATH env var (no constructor)
- Deleted SkiaRunner project (test project replaces it)
- ReferenceGenerator converted from console app to xUnit test project
- ReferenceComparisonTests discovers scenarios via directory scan +
reflection instead of AllScenarios registry
- CI generate_references job uses dotnet test
- Updated copilot instructions
421 tests pass, 0 failures, ApiCompat clean.
Co-authored-by: Copilot <[email protected]>
Replace SKBitmap + 64 SetPixel P/Invoke calls with: - stackalloc uint[64] for the pixel buffer (256 bytes on stack) - Single SKImage.FromPixelCopy bulk transfer - No managed heap allocations for the tile Co-authored-by: Copilot <[email protected]>
Co-authored-by: Copilot <[email protected]>
Patterns were vertically flipped — GDI+ anchors from row 0 (top), our data had them at row 7 (bottom). Extracted correct bitmasks by reading 8×8 pixel tiles from Windows CI GDI+ reference images. Result: 48 hatch failures → 3 (only diagonal AA patterns remain). Also cleaned orphan *Advanced/*Extended reference image dirs. Co-authored-by: Copilot <[email protected]>
SKColorF and color space testing confirmed the ±1 gradient rounding is in the final float→byte quantization step, not the interpolation math. SKColorF sRGB/linear produce identical byte output to SKColor. Use SKPixelComparer.Compare(skia, gdi, tolerance: 3) which allows |ΔR| + |ΔG| + |ΔB| ≤ 3 per pixel (±1 per channel). This correctly passes gradient rounding while still catching real rendering bugs. Result: 135 → 116 failures (19 gradient rounding tests now pass) Co-authored-by: Copilot <[email protected]>
GDI+ only enables AA for SmoothingMode.AntiAlias and HighQuality. Default, None, HighSpeed, and Invalid all render without AA. Our code was enabling AA for everything except None and HighSpeed, which caused scenarios without explicit SmoothingMode.None to render with smooth edges while GDI+ rendered with aliased edges. Fixed: ApplyState now only sets IsAntialias=true for AntiAlias and HighQuality modes. Co-authored-by: Copilot <[email protected]>
Test shapes: triangle (3 colors), square (4 colors), pentagon (5), star (10 vertices, single color), ellipse, off-center point, single color, and L-shape (concave polygon). All currently render as simple radial gradients using only the first surround color — the per-vertex color interpolation is not implemented. Co-authored-by: Copilot <[email protected]>
406 GDI + 406 Skia reference images. Local matches CI: 241/406 passing. Co-authored-by: Copilot <[email protected]>
Replace radial gradient approximation with SKCanvas.DrawVertices using TriangleFan mode with per-vertex colors. This produces gradients that follow the path shape with per-vertex color interpolation. - Flatten bezier/quadratic path segments to polyline vertices - Build triangle fan: center (CenterColor) + boundary (SurroundColors) - Clip to path for concave shapes - Route FillPath, FillRectangle, FillEllipse through FillOnCanvas when brush is PathGradientBrush Results: Triangle/Square/Pentagon/Star now render with correct per-vertex color blending. Star went from 100% to 25% error. Co-authored-by: Copilot <[email protected]>
Skia represents ellipses/arcs as conic sections (rational quadratics), not cubic beziers. Added SKPathVerb.Conic handling with weighted subdivision to produce boundary points. Ellipse PathGradient now renders correctly (yellow→blue) instead of all-white. Error dropped from 50% to 35%. Co-authored-by: Copilot <[email protected]>
RotateFlipType encodes rotation in bits 0-1 and flip in bit 2. The previous code compared enum member names but the enum has overlapping aliases (e.g. RotateNoneFlipX=4=Rotate180FlipY), so the flip flags were never set correctly. Fixed by decoding the numeric value directly: - Bits 0-1: rotation (0°, 90°, 180°, 270°) - Bit 2: horizontal flip For 90°/270° rotations, the flip axis must be swapped (X→Y) because the coordinate system is rotated. Result: 11 RotateFlip tests now pass (242 → 253 total passing). Co-authored-by: Copilot <[email protected]>
12 files updated: - Image.cs: RotationMask, FlipXMask, Rotation90/180/270, DefaultDpi - Graphics.cs: GdiPixelCenterOffset, GdiTensionFactor, DefaultCurveTension, DefaultTextContrast, TextEmPaddingDivisor, CubicBezierStride - HatchBrush.cs: HatchStyle.SolidDiamond for max index, tileSize, msbMask - SkiaConversions.cs: DashLength, DotLength, GapLength for dash patterns - Font.cs: PointsPerInch, DocumentUnitsPerInch, MillimetersPerInch - GraphicsPath.cs: GdiTensionFactor, DefaultDpi, PointsPerInch - GraphicsPathIterator.cs: PathPointType enum refs instead of hex literals - PathGradientBrush.cs: QuadSubdivisions, CubicConicSubdivisions - Bitmap.cs: BitsPerByte - ColorTranslator.cs: channel masks and shifts - PrinterUnitConvert.cs: unit conversion factors - StandardPrintController.cs: PointsPerInch, HundredthsPerInch Co-authored-by: Copilot <[email protected]>
406 GDI + 406 Skia. Local: 252/406 passing (62.1%). RotateFlip fix confirmed: BitmapOperations 13 → 2 failures. Co-authored-by: Copilot <[email protected]>
Pen.Transform: - Extract X scale from transform matrix, multiply stroke width PenAlignment.Inset: - Clip to shape boundary, double stroke width so only inner half shows - Pen_Alignment_Inset: 16.7% → passing ✅ CompoundArray: - Multi-stroke railroad track via GetFillPath + SKPathOp.Difference - Pen_CompoundArray: 16.2% → 3.3% StartCap: - Use StartCap when equal to EndCap (was always using EndCap) Refactored all Draw methods through central DrawStroke() helper that handles normal, inset, and compound pen modes. Co-authored-by: Copilot <[email protected]>
Documented honestly: - Pen.Transform: scale-only, no rotation/shear - StartCap vs EndCap: single cap fallback when different - Anchor caps: not implemented (RoundAnchor, DiamondAnchor, etc.) - DashCap: stored but not applied - PenAlignment.Inset: clip trick, not true inset - CompoundArray: GetFillPath approximation - PathGradientBrush: triangle fan (barycentric) vs GDI+ ray interpolation - Blend/InterpolationColors on PathGradient: not applied to fan - PixelOffsetMode.Half/HighQuality: stored, not applied - CompositingMode.SourceCopy: stored, not applied - Diagonal hatch AA: Skia no-AA vs GDI+ sub-pixel blending - Gradient rounding: ±1 per channel, per-pixel tolerance of 3 - Cardinal spline: tension*0.3 (Wine) vs tension/3 (standard) - SmoothingMode.Default: no AA (matching GDI+) - DrawImage: boundary sampling differences Co-authored-by: Copilot <[email protected]>
CompositingMode.SourceCopy: - ApplyState now sets paint.BlendMode = Src for SourceCopy - DrawImageCore also applies compositing mode - Compositing_SourceCopy: 25% → passing ✅ PixelOffsetMode.Half/HighQuality: - Property setter applies -0.5px canvas translate - Restore() re-applies offset after canvas state restore - PixelOffset_Half: 2.2% → passing ✅ - PixelOffset_HighQuality: 2.2% → passing ✅ SaveRestore clip: - Save() creates clip scope so SetClip(Replace) doesn't leak past - SaveRestore_Clip: 9% → passing ✅ Bitmap_GetSetPixel (63%): - Investigated: bilinear interpolation sampling difference when upscaling checkerboard. Not fixable. Documented in KNOWN-LIMITATIONS. Updated KNOWN-LIMITATIONS.md to reflect implemented features. Co-authored-by: Copilot <[email protected]>
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SkiaSharp.Extended.Drawing.Common
A cross-platform replacement for
System.Drawing.Commonbacked entirely by SkiaSharp. Same namespace, same API surface — reference the NuGet and existingSystem.Drawingcode runs on macOS, Linux, iOS, Android, and everywhere SkiaSharp runs.Why?
System.Drawing.Commonis Windows-only on .NET 6+. Thousands of apps and libraries depend on its API for 2D rendering, image manipulation, and printing. This package provides the same API backed by SkiaSharp so that code written againstSystem.Drawingcontinues to work without rewriting.How It Works
All types live in the
System.Drawing/System.Drawing.Drawing2D/System.Drawing.Imaging/System.Drawing.Text/System.Drawing.Printingnamespaces, exactly matching the original. Under the hood, every type delegates to SkiaSharp:GraphicsSKCanvasBitmap/ImageSKBitmapPenSKPaint(stroke)SolidBrush,TextureBrush,LinearGradientBrush,HatchBrush,PathGradientBrushSKPaint/SKShaderGraphicsPathSKPathMatrixSKMatrixFont/FontFamilySKFont/SKTypefaceRegionSKPath+SKPath.OpPrintDocumentSKDocument.CreatePdfBrushes/PensGDI+ Coordinate Compatibility
GDI+ has a quirk: it offsets curve coordinates by +0.5 pixels for rasterization. We replicate this exactly via
GdiCurveRect()andGdiPolygonPath()helpers, bringing pixel error from ~3% down to < 0.1% for solid fills and < 0.5% for non-antialiased geometry.Benchmarks (GDI+ vs SkiaSharp)
Measured on Windows CI with BenchmarkDotNet (ShortRun, .NET 10.0.7, X64 RyuJIT AVX2). Operations are 1000 iterations over a 500×500 bitmap.
Skia Faster
GDI+ Faster
API Coverage
PlatformNotSupportedException— these are all genuinely Windows-only: HDC/HWND handles, EMF/WMF metafiles,CopyFromScreen, GDI+ object handlesdotnet apicompat --strict-modePixel Validation
Every drawing feature has paired test scenarios that render the same code through both real
System.Drawing(GDI+ on Windows) and our SkiaSharp wrapper. The outputs are diffed pixel-by-pixel — 121 scenarios across 26 categories with 242 reference images checked in.Known Limitations
See
KNOWN-LIMITATIONS.mdfor the full list of unimplemented methods, partial implementations (ImageAttributes gamma/threshold, character-level text trimming, sub-byte LockBits formats), and cross-platform rendering differences.