Meziantou.FrameworkGradientBrush Class
A brush painting a transition between colors: a LinearGradientBrush, a RadialGradientBrush or a SweepGradientBrush.
public abstract class GradientBrush : BrushRemarks
The color of a pixel is the color of the gradient at the center of that pixel. Each position of the canvas has a parameter (0 at the start of the gradient, 1 at its end), brought back into that range by GradientBrush.SpreadMode. The color is the color of the last stop whose offset is not greater than the parameter, interpolated with the next stop; before the first stop it is the color of the first stop. Two stops with the same offset make a hard edge.
The stops are converted to the pixel format of the frame first, then interpolated on alpha-premultiplied values (a transparent stop does not darken its neighbors), on the encoded sample values, and rounded to nearest with ties upward. GradientBrush.ColorSpace selects another space to mix the colors in: linear light, Oklab or Oklch. A gradient whose stops all have the same color paints exactly what a SolidBrush of that color paints.
- Inheritance
BrushGradientBrush
Properties
| Name | Description |
|---|---|
| ColorSpace | Gets the space in which the colors of two stops are mixed. Defaults to GradientColorSpace.Encoded. |
| Dither | Gets a value indicating whether the colors of the gradient are dithered on a canvas of 8 bits per component, so that a slow transition does not show as bands. Defaults to false. |
| SpreadMode | Gets the colors outside the range of the stops. Defaults to GradientSpreadMode.Pad. |
| Stops | Gets the stops, in increasing order of offset. |
| Transform | Gets the transformation that places the gradient on the canvas: the points and the lengths of the gradient are given before it is applied. Defaults to the identity. |
ColorSpace
GradientBrush.csGets the space in which the colors of two stops are mixed. Defaults to GradientColorSpace.Encoded.
public GradientColorSpace ColorSpace { get; init; }Property value
Exceptions
ArgumentOutOfRangeException- The value is not a defined
GradientColorSpace.
Remarks
In a space other than GradientColorSpace.Encoded, the stops are interpolated as 16-bit sRGB colors, on alpha-premultiplied values of that space, and the result is converted to the pixel format of the frame like any brush color; a color the interpolation takes out of sRGB is brought back to its nearest sample values. The colors come from the power and the cube root functions of the platform, as those of ResizeWorkingSpace.LinearSrgb do: a sample whose exact value is within about 1e-12 of a rounding boundary can differ by one from a platform to another.
Dither
GradientBrush.csGets a value indicating whether the colors of the gradient are dithered on a canvas of 8 bits per component, so that a slow transition does not show as bands. Defaults to false.
public bool Dither { get; init; }Property value
Remarks
A dithered pixel is rounded up or down to one of the two nearest samples, by an ordered pattern (the 8x8 Bayer matrix, placed on the pixels of the frame from its top-left corner) instead of to the nearest one: over a few pixels, the samples average to the color between two steps. The same threshold is used for the color and the alpha of a pixel. The pattern is fixed: the same drawing gives the same pixels.
A color that a frame of 8 bits per component holds exactly, such as the color of a stop, is not changed. A frame of 16 bits per component or of floating-point components, whose steps do not show, is not dithered, and neither are the colors of a gradient that are not drawn on a frame (the paints of color glyphs).
SpreadMode
GradientBrush.csGets the colors outside the range of the stops. Defaults to GradientSpreadMode.Pad.
public GradientSpreadMode SpreadMode { get; init; }Stops
GradientBrush.csGets the stops, in increasing order of offset.
public ReadOnlyMemory<GradientStop> Stops { get; }Property value
Transform
GradientBrush.csGets the transformation that places the gradient on the canvas: the points and the lengths of the gradient are given before it is applied. Defaults to the identity.
public AffineTransform Transform { get; init; }Property value
Remarks
The color of a pixel is the color the gradient has, before the transformation, at the position the center of the pixel comes from. A scaling that is not the same on both axes turns the circles of a radial gradient into ellipses. With a transformation that flattens the plane to a line or a point, the whole canvas has the color of the last stop.