Convert graphics VB6 to .net

PeterGans · September 3rd, 2011, 04:27 PM

I'm at last converting programs from VB6 to .NEt.

In VB6 I draw a graph on a picture box using methods like "line" to draw a line from one point to another. In VB.net a picture box does not appear to be a graphics object. I can't see how to get started. How do I draw a line from point x1,y1 to point x2,y2 on an object comparable to the picture box in VB6?

Rod Stephens · September 4th, 2011, 10:36 AM

Graphics is the hardest thing to convert from VB 6 to VB .NET. For a lot of information about using graphics in .NET, see my Wrox Blox:

Visual Basic Graphics Programming
http://www.wrox.com/WileyCDA/WroxTit...470343486.html

It provides a good introduction for only $6.99.

The key ideas are:

There is a PictureBox control but it doesn't provide drawing methods. Instead it can either display an image or draw in its Paint event handler. (The Form can do the same).

The Paint event handler provides a Graphics object, and that object provides drawing methods such as DrawLine and FillRectangle. You can think of the Graphics object as the surface on which you draw.

You can also get a Graphics object by creating a Bitmap like this:

Code:

Dim bm As New Bitmap(100, 100)
Dim gr As Graphics = Graphics.FromImage(bm)
gr.DrawLine(Pens.Red, 0, 0, 100, 50)

You use Pen objects to determine how lines are drawn. For example, to set their color, thickness, dash styles, etc.

You use Brushes to determine how areas and text are filled. For example, to set their color and fill pattern.

That's the extremely quick overview. Search online for more examples. The VB Helper web site has lots of graphics examples. Try looking at:

http://www.vb-helper.com/index_graphics.html

Of look at that Wrox Blox I mentioned, or read the chapters about graphics in this forum's book Visual Basic 2010 Programmer's Reference.

Finally if you get stuck and need a hint, post a new question here or email me directly (RodStephens@vb-helper.com).

Good luck!

PeterGans · September 4th, 2011, 12:05 PM

Here's a follow up. When the line is used as a cursor I use picturebox.drawmode=7 (XOR). What's the equivalent in VB 8? I can't see anything relevant in pen or brush properties.

Rod Stephens · September 5th, 2011, 11:42 AM

One of the stranger omissions in GDI+ graphics is drawing modes like XOR. You just can't do it.

Instead what you normally do is make a copy of the Bitmap on which you are drawing, draw on the copy, and then display it. When you need to erase, you just make anotehr copy of the original.

To make a line contrast with whatever is is over (like XOR would provide), you can draw with a dashed line.

All this is less efficient than drawing in XOR mode but the GDI+ graphics used by .NET are around 20x faster than the graphics methods used by VB 6 so the end result is faster.