Visual Basic Graphics

In VB, graphics capabilities are usually associated with drawing lines, boxes, or otherwise manipulating the display. Graphics are usually created on something, which in the case of VB is either the printer, the screen, or the picture control. All three represent a surface to which graphics can be applied. No other control supplied with VB supports the graphics features.

I'll first walk through the graphical methods and properties which VB supports and then discuss them one at a time to help you understand how they play together.

Here are graphics methods which VB supports.

• Circle - as you expect, draws a circle or an ellipse
  
• Cls - clears all graphics
  
• Line - draws a straight line
  
• PaintPicture - draws the contents of a graphics file
  
• Point - returns the color of a point
  
• Print - used for printing text
  
• Pset - sets the color of a specific pixel

Likewise, here are the graphics properties which VB supports.

• AutoRedraw - Determines if graphics are automatically redrawn if something moves in front of them
  
• ClipControls - Determines how repainting of graphics is handled
  
• DrawMode - Sets the appearance of a graphics method
  
• DrawStyle - Sets the line style for output from graphics methods
  
• DrawWidth - Sets the line width for output from graphics methods
  
• FillColor - Sets the color used to fill circles, lines and boxes
  
• FillStyle - Sets the pattern used to fill circle, lines and boxes
  
• FontTransparent - Determines if the font is printed with a transparent background
  
• Palette - Sets the image containing the palette to use for a control
  
• PaletteMode - Determines which palette to use for the controls on a object
  
• RightToLeft - Indicates the text display direction.
  
• ScaleHeight - Sets the height of the client area
  
• ScaleLeft - Sets the starting value of the left of the client area
  
• ScaleTop - Sets the starting value of the top of the client area
  
• ScaleWidth - Sets the width of the client area
  
• ScaleMode - Sets the units of the scale

color:black Scales 

• oints
  Points are the same as you're used to seeing associated with a font. 72 points make an inch. Typically point sizes for typed text range from 10-12 for most documents.
  
• Twips
  VB also introduces a unit known as a twip, where there are 1440 twips to the inch. The twip gives more resolution to measurements than the point (1 twip = 1/20 of a point), making possible more accurate graphics
  
• Characters
  Uses fixed twips (120 twips per horizontal character and 240 twips per vertical character) definitions.
  
  User
  In this case, the name "user" means user-defined. This is one of the most powerful units you can use as a scale. Here, you define the number of units within the client area

ScaleMode
The ScaleMode property simply identifies which units are to be used. You can set it to any of the units I've already discussed above. Once you pick a scalemode, VB adjusts the size properties of the client area to match the selection.

color:black Using Graphics Methods
 

• Circle
  In this code, I simply draw 10 circles, progressively moving the center to the right starting from the coordinate of X=500.

For i = 1 to 1000 Step 100

   picture1.circle (i + 500, 1000), 400, vbGreen

Next i

Cls
It doesn't get any simpler:

picture1.cls

The .cls methods will erase all graphics which have been drawn on the object, in this case the picturebox.

• Line
  Similar to the use of the circle method, this example simply creates 10 vertical lines, positioned from left to right.

For i = 1 to 1000 Step 100

picture1.line (i+500,500)-(i+500,4000), vbBlue

Next i

The line method can also draw boxes by simply adding an extra argument to the code as follows:

For i = 1 to 4000 Step 400

   picture1.line (i+200,500)-(i+400,3000), vbBlue, BF

Next i

The BF added at the end of the line of code simply tells VB to draw a filled box instead of a line.

• PaintPicture
  
• Point

i  = picture1.point (100,500)

Here, the color of the point located at X=100 and Y=500 is assigned to the variable i. In my own experience I haven't had any reason to use this method.

• Pset
  This is the most basic drawing tool VB has to offer. With PSET you can set the color of any point within the client area of the drawing surface. For example, the next code randomly picks a color and randomly picks a coordinate at which to set the color. For no good reason I limit the number of points plotted to 1000

mso-list:Ignore 10.0pt mso-bidi-9.5pt font-family:Symbol mso-fareast-font-family:Symbol mso-bidi-font-family:Symbol color:black · font:7.0pt "Times New Roman"'                9.5ptfont-family: "Courier New"For i = 1 to 1000

pick color value from 0 to 15 (the QBasic standard color set)

Int(15*Rnd)+0)

pick X from 0 to ScaleWidth

   X = (Int((Picture1.ScaleWidth * Rnd) + 0))

pick Y from 0 to ScaleHeight

   Y = (Int((Picture1.ScaleHeight * Rnd) + 0))

now plot the data

   picture1.pset (X,Y), QBColor( iColor)

Next i

Note: To get a value from n to 15, replace the "0" with the value of n

With PSET you can do almost any graphic you can imagine, limited only by the difficulty in controlling one point at a time. Also, the PSET method is not nearly so fast as some of the higher order graphics methods.