LinearGradientBrush::SetBlendBellShape method (gdiplusbrush.h)

Article
10/13/2021

The LinearGradientBrush::SetBlendBellShape method sets the blend shape of this linear gradient brush to create a custom blend based on a bell-shaped curve.

Syntax

Status SetBlendBellShape(
  [in] REAL focus,
  [in] REAL scale
);

Parameters

[in] focus

Type: REAL

Real number that specifies the position of the ending color. This number is a percentage of the distance between the boundary lines and must be in the range from 0.0 through 1.0.

[in] scale

Type: REAL

Optional. Real number that specifies the percentage of the gradient's ending color that gets blended, at the focus position, with the gradient's starting color. This number must be in the range from 0.0 through 1.0. The default value is 1.0, which specifies that the ending color is at full intensity.

Return value

Type: Status

If the method succeeds, it returns Ok, which is an element of the Status enumeration.

If the method fails, it returns one of the other elements of the Status enumeration.

Remarks

By default, the color changes gradually from the starting color (color at the starting boundary of the linear gradient brush) to the ending color (color at the ending boundary of the linear gradient brush) as you move from the starting boundary to the ending boundary. You can customize the positioning and blending of the starting and ending colors by using the LinearGradientBrush::SetBlendBellShape method.

The LinearGradientBrush::SetBlendBellShape method customizes the blend so that it follows a bell-shaped curve with the extremes of the bell's base at the gradient's boundaries. The starting color, which, in a default blend, is at the starting boundary of a linear gradient brush, appears at the starting and ending boundaries of the linear gradient brush when a bell-shaped blend is applied. The position of the ending color, which, in a default blend, is at the ending boundary, is somewhere between the boundaries and is determined by the value of the focus. In other words, the focus specifies the position of the peak of the bell. For example, a focus value of 0.7 places the peak at 70 percent of the distance between the starting and ending boundaries. The ending color appears at this peak.

The ending color in a bell-shaped blend is a percentage of the gamut between the gradient's default-blend starting color and default-blend ending color. For example, suppose a linear gradient brush is constructed with red as the starting color and blue as the ending color. If LinearGradientBrush::SetBlendBellShape is called with a scale value of 0.8, the ending color in the bell shaped blend is a hue that is 80 percent between red and blue (20 percent red, 80 percent blue). A scale value of 1.0 produces an ending color that is 100 percent blue.

Examples

The following example creates a linear gradient brush, sets a bell-shaped blend, and uses the brush to fill a rectangle. Twice more, the code sets a bell-shaped blend with different values and, each time, uses the brush to fill a rectangle.

VOID Example_SetBlendBell(HDC hdc)
{
   Graphics myGraphics(hdc);

   LinearGradientBrush linGrBrush(
      Point(0, 0),
      Point(500, 0),
      Color(255, 255, 0, 0),   // red
      Color(255, 0, 0, 255));  // blue

   linGrBrush.SetBlendBellShape(0.5f, 0.6f);
   myGraphics.FillRectangle(&linGrBrush, 0, 0, 500, 50);

   linGrBrush.SetBlendBellShape(0.5f, 0.8f); 
   myGraphics.FillRectangle(&linGrBrush, 0, 75, 500, 50);

   linGrBrush.SetBlendBellShape(0.5f, 1.0f); 
   myGraphics.FillRectangle(&linGrBrush, 0, 150, 500, 50);
}

Requirements

Requirement	Value
Minimum supported client	Windows XP, Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	gdiplusbrush.h (include Gdiplus.h)
Library	Gdiplus.lib
DLL	Gdiplus.dll