Drawing a Shaded Triangle

To draw a shaded triangle, define a TRIVERTEX structure with three elements and a single GRADIENT_TRIANGLE structure. The following code example shows how to draw a shaded triangle using the GradientFill function with the GRADIENT_FILL_TRIANGLE mode defined.

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
 int wmId, wmEvent;
 PAINTSTRUCT ps;
 HDC hdc;

 switch (message)
 {
 case WM_COMMAND:
 wmId = LOWORD(wParam);
 wmEvent = HIWORD(wParam);
 // Parse the menu selections:
 switch (wmId)
 {
 case IDM_ABOUT:
 DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
 break;
 case IDM_EXIT:
 DestroyWindow(hWnd);
 break;
 default:
 return DefWindowProc(hWnd, message, wParam, lParam);
 }
 break;
 case WM_PAINT:
 {hdc = BeginPaint(hWnd, &ps);
// Create an array of TRIVERTEX structures that describe
// positional and color values for each vertex.
TRIVERTEX vertex[3];
vertex[0].x = 150;
vertex[0].y = 0;
vertex[0].Red = 0xff00;
vertex[0].Green = 0x8000;
vertex[0].Blue = 0x0000;
vertex[0].Alpha = 0x0000;

vertex[1].x = 0;
vertex[1].y = 150;
vertex[1].Red = 0x9000;
vertex[1].Green = 0x0000;
vertex[1].Blue = 0x9000;
vertex[1].Alpha = 0x0000;

vertex[2].x = 300;
vertex[2].y = 150; 
vertex[2].Red = 0x9000;
vertex[2].Green = 0x0000;
vertex[2].Blue = 0x9000;
vertex[2].Alpha = 0x0000;

// Create a GRADIENT_TRIANGLE structure that
// references the TRIVERTEX vertices.
GRADIENT_TRIANGLE gTriangle;
gTriangle.Vertex1 = 0;
gTriangle.Vertex2 = 1;
gTriangle.Vertex3 = 2;

// Draw a shaded triangle.
GradientFill(hdc, vertex, 3, &gTriangle, 1, GRADIENT_FILL_TRIANGLE);
 EndPaint(hWnd, &ps);
 break;}
 case WM_DESTROY:
 PostQuitMessage(0);
 break;
 default:
 return DefWindowProc(hWnd, message, wParam, lParam);
 }
 return 0;
}

The following image shows the drawing output of the preceding code example.

👁 illustration showing a triangle that fills from orange at the top point to magenta on the bottom edge

Related topics

Bitmaps Overview

Bitmap Functions

Drawing a Shaded Rectangle

EMRGRADIENTFILL

GRADIENT_TRIANGLE

GradientFill

TRIVERTEX