Tip 205: Drawing a Gradient Background Pattern on Forms in Visual Basic 4.0

February 28, 1996

Abstract

The Microsoft® Visual Basic® version 4.0 Setup program allows you to create a standard installation program for your Visual Basic application. The Setup program, as with other Microsoft Setup programs, draws a gradient background pattern, usually in a blue color. This article explains how to draw gradient backgrounds in a Visual Basic application.

Using the RealizePalette Function to Draw Backgrounds

Most Microsoft® Windows® applications are installed by running a Setup program. These setup programs often display a window in which appears a faded blue background. This same effect can be reproduced in Microsoft Visual Basic® version 4.0 applications by using the Windows application programming interface (API) RealizePalette function.

To display a window with a gradient background, you simply paint thin rectangles in different colors on the form. This gives the form a fade-to-black effect.

The RealizePalette function lets you select a logical palette for a device context, such as a window. This allows you to use a larger number of colors in your application without interfering with the colors used by other forms (windows) in your program. After calling the RealizePalette function, you need only select the colors with which you want to paint the rectangles and the gradient background effect is created.

Example Program

This program shows how to draw a gradient background on a form/window in Visual Basic.

1. Create a new project in Visual Basic. Form1 is created by default.
   
   
2. Add the following code to the General Declarations section of Form1 (note that the Declare statement must be typed as a single line of code):

   Private Declare Function RealizePalette Lib "gdi32" 
      (ByVal hdc As Long) As Long
   
   Dim RedColor(256) As Integer
   Dim GreenColor(256) As Integer
   Dim BlueColor(256) As Integer
   

3. Add the following code to the Form_Load event for Form1:

   Private Sub Form_Load()
       For I = 1 To 256
           RedColor(I) = 1
           GreenColor(I) = 1
           BlueColor(I) = I
       Next I
   End Sub
   

4. Add a Command Button control to Form1. Command1 is created by default.
   
   
5. Add the following code to the Click event for Command1:

   Private Sub Command1_Click()
       dummy = RealizePalette(Form1.hdc)
       Form1.Scale (0, 0)-(256, 1)
       For I = 0 To 255
           Form1.Line (I, 0)-(I + 1, 1), RGB(RedColor(I + 1), _
               GreenColor(I + 1), BlueColor(I + 1)), BF
           Form1.ForeColor = RGB(RedColor(I + 1), GreenColor(I + 1), _
               BlueColor(I + 1))
       Next I
   End Sub
   

6. Add a second Command Button control to Form1. Command2 is created by default.
   
   
7. Add the following code to the Click event for Command2:

   Private Sub Command2_Click()
       dummy = RealizePalette(Form1.hdc)
       Form1.Scale (0, 0)-(1, 256)
       For I = 0 To 255
           Form1.Line (0, I)-(1, I + 1), RGB(RedColor(I + 1), _
           GreenColor(I + 1), BlueColor(I + 1)), BF
           Form1.ForeColor = RGB(RedColor(I + 1), GreenColor(I + 1), _
           BlueColor(I + 1))
       Next I
   End Sub
   

Run the example program by pressing  When you click the first Command Button control, the program draws the black-to-blue gradient background horizontally across the form. Clicking the second Command Button control instructs the program to draw the gradient background vertically down the form.

Additional References

"Color Palettes." (MSDN Library, SDK Documentation, Platform SDK)

Knowledge Base Q128637. "How to Draw a Gradient Background."

"RealizePalette QuickInfo Overview Group." (MSDN Library, SDK Documentation, Platform SDK)