GdiGradientFill function
The GdiGradientFill function fills rectangle and triangle structures.
Syntax
BOOL GdiGradientFill( _In_ HDC hdc, _In_ PTRIVERTEX pVertex, _In_ ULONG dwNumVertex, _In_ PVOID pMesh, _In_ ULONG dwNumMesh, _In_ ULONG dwMode );
Parameters
 hdc [in]

A handle to the destination device context.
 pVertex [in]

A pointer to an array of TRIVERTEX structures that each define a triangle vertex.
 dwNumVertex [in]

The number of vertices in pVertex.
 pMesh [in]

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

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

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 32bpp modes. Dithering is performed in 16, 8, 4, and 1bpp 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 upperleft and lowerright coordinates of the rectangle. There are two shading modes used when drawing a rectangle. In horizontal mode, the rectangle is shaded from lefttoright. In vertical mode, the rectangle is shaded from toptobottom. 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 upperleft and lowerright 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 pixelperfect 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
Minimum supported client  Windows 2000 Professional [desktop apps only] 

Minimum supported server  Windows 2000 Server [desktop apps only] 
Header 

Library 

DLL 

See also