GdiGradientFill function (wingdi.h)

The GdiGradientFill function fills rectangle and triangle structures.

Syntax

BOOL GdiGradientFill(
  [in] HDC        hdc,
  [in] PTRIVERTEX pVertex,
  [in] ULONG      nVertex,
  [in] PVOID      pMesh,
  [in] ULONG      nCount,
  [in] ULONG      ulMode
);

Parameters

[in] hdc

A handle to the destination device context.

[in] pVertex

A pointer to an array of TRIVERTEX structures that each define a triangle vertex.

[in] nVertex

The number of vertices in pVertex.

[in] pMesh

An array of GRADIENT_TRIANGLE structures in triangle mode, or an array of GRADIENT_RECT structures in rectangle mode.

[in] nCount

The number of elements (triangles or rectangles) in pMesh.

[in] ulMode

The gradient fill mode. This parameter can be one of the following values.

Value	Meaning
GRADIENT_FILL_RECT_H	In this mode, two endpoints describe a rectangle. The rectangle is defined to have a constant color (specified by the TRIVERTEX structure) for the left and right edges. GDI interpolates the color from the left to right edge and fills the interior.
GRADIENT_FILL_RECT_V	In this mode, two endpoints describe a rectangle. The rectangle is defined to have a constant color (specified by the TRIVERTEX structure) for the top and bottom edges. GDI interpolates the color from the top to bottom edge and fills the interior.
GRADIENT_FILL_TRIANGLE	In this mode, an array of TRIVERTEX structures is passed to GDI along with a list of array indexes that describe separate triangles. GDI performs linear interpolation between triangle vertices and fills the interior. Drawing is done directly in 24- and 32-bpp modes. Dithering is performed in 16-, 8-, 4-, and 1-bpp mode.

Return value

If the function succeeds, the return value is TRUE.

If the function fails, the return value is FALSE.

Remarks

Note  This function is the same as GradientFill.

 

To add smooth shading to a triangle, call the GdiGradientFill function with the three triangle endpoints. GDI will linearly interpolate and fill the triangle. Here is the drawing output of a shaded triangle. To add smooth shading to a rectangle, call GdiGradientFill with the upper-left and lower-right coordinates of the rectangle. There are two shading modes used when drawing a rectangle. In horizontal mode, the rectangle is shaded from left-to-right. In vertical mode, the rectangle is shaded from top-to-bottom. Here is the drawing output of two shaded rectangles - one in horizontal mode, the other in vertical mode. The GdiGradientFill function uses a mesh method to specify the endpoints of the object to draw. All vertices are passed to GdiGradientFill in the pVertex array. The pMesh parameter specifies how these vertices are connected to form an object. When filling a rectangle, pMesh points to an array of GRADIENT_RECT structures. Each GRADIENT_RECT structure specifies the index of two vertices in the pVertex array. These two vertices form the upper-left and lower-right boundary of one rectangle.

In the case of filling a triangle, pMesh points to an array of GRADIENT_TRIANGLE structures. Each GRADIENT_TRIANGLE structure specifies the index of three vertices in the pVertex array. These three vertices form one triangle.

To simplify hardware acceleration, this routine is not required to be pixel-perfect in the triangle interior.

Note that GdiGradientFill does not use the Alpha member of the TRIVERTEX structure. To use GdiGradientFill with transparency, call GdiGradientFill and then call GdiAlphaBlend with the desired values for the alpha channel of each vertex.

For more information, see Smooth Shading, Drawing a Shaded Triangle, and Drawing a Shaded Rectangle.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	wingdi.h (include Windows.h)
Library	Gdi32.lib
DLL	Gdi32.dll

See also

Bitmap Functions

Bitmaps Overview

EMRGRADIENTFILL

GRADIENT_RECT

GRADIENT_TRIANGLE

TRIVERTEX