Class SkiaHelper
Provides utility methods and helpers for working with SkiaSharp, a 2D graphics library. This class contains methods that do not use Alternet.UI.
public static class SkiaHelper- Inheritance
-
SkiaHelper
Remarks
This class contains static methods designed to simplify common tasks when using SkiaSharp. It is intended to be a central place for reusable SkiaSharp-related functionality.
Fields
- DefaultAntialiasing
Gets or sets default value for IsAntialias property when SKPaint is created by the conversion methods.
- NativeLibraryName
Represents the name of the SkiaSharp native library.
- SKCanvasDrawPointsName
Represents the name of the SkiaSharp canvas method used to draw points.
- SampleCharsForIsMonospace
A sample string containing characters commonly used to test whether a font is monospaced.
- SpanStackLimit
Represents the maximum number of spans that can be stored in a stack.
Properties
- DefaultFont
Gets or sets default font for use with SkiaSharp.
- DefaultFontName
Gets or sets default font name for use with SkiaSharp.
- DefaultFontSize
Gets or sets default font size for use with SkiaSharp.
- DefaultMonoFontName
Gets or sets default fixed-pitch font name.
- DefaultTypeFace
Gets or sets default SKTypeface using to create default SkiaSharp font.
- FocusRectPaint
Gets or sets the paint object used to render the focus rectangle.
- FontFamilies
Gets all installed font families as array of strings.
- GrayscaleColorFilter
Gets or sets the SKColorFilter used to convert images to grayscale.
- IsDefaultMonoFontNameAssigned
Gets a value indicating whether the default monospaced font name has been assigned.
- NullCanvas
Gets a null SKCanvas instance that performs no drawing operations.
Methods
- ApplyPixelSnapping(SKCanvas)
Convenience: apply the pixel-snapping translate to the canvas. It saves the canvas state and returns an IDisposable that restores when disposed: using (ApplyPixelSnapping(canvas)) { ... } // paints inside will be offset
- BitmapIsOk(SKBitmap?)
Gets whether or not specified bitmap is ok.
- CharSize(SKCanvas, char, SKFont)
Measures the size of a single character when drawn using the specified font.
- CharSize(SKCanvas, char, int, SKFont)
Returns the size of a sequence of identical characters when drawn with the specified font.
- ConvertToGrayscale(SKBitmap)
Converts the specified SKBitmap to a grayscale version using a color filter.
- CreateBitmapCanvas(SKBitmap, float)
Creates canvas on the specified bitmap.
- CreateBitmapCanvas(SKSize, float, bool)
Creates canvas on the bitmap with the specified size and scaling factor.
- CreateDefaultFont()
Creates default font.
- CreateFillPaint(SKColor)
Creates SKPaint with Fill style for the specified SKColor value.
- CreateFocusRectPaint(SKColor, float, float, float, float, bool, bool, SKStrokeCap)
Creates an SKPaint configured to draw a focus-like dashed rectangle (similar to WinForms DrawFocusRectangle). The returned SKPaint must be disposed by the caller.
- CreateNullCanvas(int, int)
Creates dummy SKCanvas object which performs not painting.
- CreateNullSurface(int, int)
Creates dummy SKSurface object ignores any painting.
- CreateStrokeAndFillPaint(SKColor)
Creates SKPaint with StrokeAndFill style for the specified SKColor value.
- CreateStrokePaint(SKColor)
Creates SKPaint with Stroke style for the specified SKColor value.
- DebugBezierPointsAssert(ReadOnlySpan<SKPoint>)
Checks whether array of SKPoint parameter is ok.
- DrawAnimatedFocusRect(SKCanvas, SKRect, SKColor, long, float, float, float, float, bool, bool)
Convenience helper that animates the dash phase to produce the "marching ants" effect. Call this from your paint loop and pass a time value (e.g. milliseconds). Uses CreateFocusRectPaint internally.
- DrawBeziers(SKCanvas, SKPaint, ReadOnlySpan<SKPoint>)
Draws a series of Bezier splines from an array of SKPoint structures.
- DrawBorderWithPaint(SKCanvas, SKPaint, SKRect, float)
Draws a border around the specified rectangle using the provided paint and border width.
- DrawDashedLine(SKCanvas, SKPoint, SKPoint, SKColor, float, SkiaDashStyle, float[]?, float, bool)
Draws a line on the canvas using a dash style similar to System.Drawing.Pen.DashStyle. This helper creates and configures an SKPaint internally (caller does not own/dispose it).
- DrawDotLine(SKCanvas, float, float, float, float, SKPaint, SKPaint?, int)
Draws a dotted line on the specified graphics context, alternating between two colors.
- DrawFocusRect(SKCanvas, SKRect, SKColor)
Draws a focus rectangle on the specified canvas using the given color. FocusRectPaint is used to draw the rectangle.
- DrawFocusRect(SKCanvas, SKRect, SKColor, float, float, float, float, bool, bool)
Draws a focus-like dashed rectangle (similar to WinForms DrawFocusRectangle). Uses CreateFocusRectPaint internally.
- DrawHorzLine(SKCanvas, SKPaint, SKPoint, float, float)
Draws a horizontal line on the specified canvas.
- DrawText(SKCanvas, ReadOnlySpan<char>, SKPoint, SKFont, SKPaint, SKPaint?)
Draws the specified text on the canvas at the given location using the specified font and paint settings.
- DrawVertLine(SKCanvas, SKPaint, SKPoint, float, float)
Draws a vertical line on the specified canvas.
- FastCeilToInt(float)
Rounds the specified floating-point value up to the nearest integer and returns the result as an int.
- FillGradient(SKCanvas, SKRect, SKColor, SKColor, SKPoint, SKPoint)
Fills the specified rectangular area on the canvas with a linear gradient.
- Fill<T>(T[], T)
Sets all elements in the specified array to the specified value.
- GetAverageCanvasScale(SKCanvas)
Returns an approximated average scale factor of the canvas transform (works with rotation/skew). Use this to convert "device-pixel" lengths into canvas units: canvasUnits = devicePixels / scale.
- GetBottomLineRect(SKRect, float)
Gets rectangle of the bottom border edge with the specified width.
- GetFontFamiliesNames()
Gets all installed font families as enumerable.
- GetLeftLineRect(SKRect, float)
Gets rectangle of the left border edge with the specified width.
- GetPathFromSystemPoints(ReadOnlySpan<Point>, SkiaFillMode)
Creates a new SKPath from a collection of drawing points, optionally specifying the fill mode.
- GetPixelSnappingOffset(SKCanvas)
Computes the pixel-snapping offset (in canvas/logical coordinates) that aligns 1px strokes to device pixel centers, taking the canvas TotalMatrix into account. Returns an SKPoint { X = offsetX, Y = offsetY } where: offsetX = 0.5f / effectiveScaleX offsetY = 0.5f / effectiveScaleY Use: canvas.Save(); canvas.Translate(offset.X, offset.Y); ... canvas.Restore();
- GetRightLineRect(SKRect, float)
Gets rectangle of the right border edge with the specified width.
- GetSKPointsForDrawWave(SKRectI)
Generates an array of points representing a wave pattern within the specified rectangular area.
- GetTextExtent(SKCanvas, ReadOnlySpan<char>, SKFont)
Gets text size.
- GetTopLineRect(SKRect, float)
Gets rectangle of the top border edge with the specified width.
- InvokeWithFilledSpan(int, char, ReadOnlySpanAction<char>, bool)
Allocates a Span<T> of the specified length, fills it with the given character, and invokes the provided action with the resulting ReadOnlySpan<T>. Uses stack allocation if the span size is below the threshold; otherwise falls back to heap.
- InvokeWithUTF8Span(ReadOnlySpan<char>, Action<nint, int>)
Converts the specified UTF-16 character span to UTF-8 and invokes the provided action with a pointer to the UTF-8 data and its length.
- IsFamilySkia(string)
Gets whether or not specified font is supported in SkiaSharp.
- IsMonospace(SKFont, float)
Returns true if the SKFont appears to be monospaced. It first checks
Typeface.IsFixedPitchif available, then measures glyph advance widths.
- PixelFromDip(SKSize, float)
Converts device-independent units to pixels.
- PixelFromDip(float, float)
Converts device-independent units to pixels.
- RecreateBitmapCanvas(ref SKCanvas?, ref float?, float, SKSize, bool)
Recreates a bitmap-backed SKCanvas with the specified scale factor and size.
- ResetFonts()
Resets loaded font families.
- SetPaintDefaults(SKPaint)
This method is called by all SKPaint create methods. It raises PaintCreated event and initializes SKPaint instance properties with the default values.
- ToDegrees(float)
Converts an angle from radians to degrees.
- ToSkia(SkiaFillMode)
Converts SkiaFillMode to SKPathFillType.
Events
- PaintCreated
Occurs when SKPaint instance is created by one of the create methods.