How to Draw a Gradient Background

• Microsoft Windows Software Development Kit (SDK) for Windows versions 3.1 and 3.0
• Microsoft Win32 Application Programming Interface (API) included with:

      - Microsoft Windows NT versions 3.1, 3.5, and 3.51
      - Microsoft Windows 95 version 4.0
  

SUMMARY

This article provides source code for drawing a gradient background pattern similar to the one used in Microsoft Setup applications. The code will compile and run on Windows version 3.1, Win32s, and Windows 95.

MORE INFORMATION

WARNING: ANY USE BY YOU OF THE CODE PROVIDED IN THIS ARTICLE IS AT YOUR OWN RISK. Microsoft provides this code "as is" without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and/or fitness for a particular purpose.

/*************************************************************
*                                                            *
*  DrawBackgroundPattern()                                   *
*                                                            *
*  Purpose: This function draws a gradient pattern that      *
*           transitions between blue and black. This is      *
*           similar to the background used in Microsoft      *
*           setup programs.                                  *
*                                                            *

void DrawBackgroundPattern(HWND hWnd)

  HDC hDC = GetDC(hWnd);  // Get the DC for the window
  RECT rectFill;          // Rectangle for filling band
  RECT rectClient;        // Rectangle for entire client area
  float fStep;            // How large is each band?
  HBRUSH hBrush;
  int iOnBand;  // Loop index

  // How large is the area you need to fill?
  GetClientRect(hWnd, &rectClient);

  // Determine how large each band should be in order to cover the
  // client with 256 bands (one for every color intensity level)
  fStep = (float)rectClient.bottom / 256.0f;

  // Start filling bands
  for (iOnBand = 0; iOnBand < 256; iOnBand++) {

    // Set the location of the current band
    SetRect(&rectFill,
            0,                           // Upper left X
            (int)(iOnBand * fStep),      // Upper left Y
            rectClient.right+1,          // Lower right X
            (int)((iOnBand+1) * fStep)); // Lower right Y

    // Create a brush with the appropriate color for this band
    hBrush = CreateSolidBrush(RGB(0, 0, (255 - iOnBand)));


    // Fill the rectangle
    FillRect(hDC, &rectFill, hBrush);

    // Get rid of the brush you created
    DeleteObject(hBrush);
  };

  // Give back the DC
  ReleaseDC(hWnd, hDC);