Table of Contents

Class CustomPaint

Namespace
Egami.Drawing
Assembly
Egami.Drawing.dll

A paint whose colors come from C# code: override Shade(int, int, Span<PremulRgbaF32>, in Matrix3x2) to fill a row of premultiplied float colors. Rows are shaded in parallel bands, so Shade(int, int, Span<PremulRgbaF32>, in Matrix3x2) must be thread-safe and must give a pixel the same color whichever band or thread asks; then the result is the same at any core count. A backend that keeps vectors, such as a PDF page, cannot run C# and draws the call through its raster fallback instead. Derive a record class from it.

public abstract record CustomPaint : Paint, ITextPaint, IEquatable<Paint>, IEquatable<CustomPaint>
Inheritance
CustomPaint
Implements
Inherited Members

Examples

// Concentric rings from C#: a record class whose Shade fills one row of premultiplied colors. It runs on several threads at
// once, so it keeps no state.
public sealed record class Rings(float Spacing) : CustomPaint
{
    public override void Shade(int y, int x, Span<PremulRgbaF32> row, in Matrix3x2 inverse)
    {
        for (int i = 0; i < row.Length; i++)
        {
            Vector2 p = Vector2.Transform(new Vector2(x + i + 0.5f, y + 0.5f), inverse);
            float v = 0.5f + (0.5f * MathF.Cos(p.Length() * MathF.Tau / Spacing));
            row[i] = new PremulRgbaF32(v, v * 0.6f, 0.2f, 1);
        }
    }
}

Constructors

CustomPaint()

Initializes a new instance of the CustomPaint class.

protected CustomPaint()

Methods

Shade(int, int, Span<PremulRgbaF32>, in Matrix3x2)

Fills one row of pixels: row[i] is the device pixel (x + i, y), whose center (x + i + 0.5, y + 0.5) maps to paint coordinates through inverse. Colors are premultiplied: each channel at most the alpha, all from 0 to 1.

public abstract void Shade(int y, int x, Span<PremulRgbaF32> row, in Matrix3x2 inverse)

Parameters

y int

The device row.

x int

The device column of the first pixel.

row Span<PremulRgbaF32>

The colors to write, one per pixel.

inverse Matrix3x2

The transform from device pixels to paint coordinates: the inverse of the local matrix then the canvas transform.

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