Obtaining and Creating Graphics Objects in Visual Basic .NET

Make QR Code 2d barcode in Visual Basic .NET Obtaining and Creating Graphics Objects

Obtaining and Creating Graphics Objects
QR Code JIS X 0510 Maker In Visual Basic .NET
Using Barcode generation for .NET Control to generate, create QR Code image in Visual Studio .NET applications.
www.OnBarcode.com
QR Code Decoder In VB.NET
Using Barcode recognizer for Visual Studio .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
Getting a Graphics object for an on-screen form or control is as easy as calling the form s or control s CreateGraphics method.
Printing Code-39 In Visual Basic .NET
Using Barcode generation for Visual Studio .NET Control to generate, create Code-39 image in .NET applications.
www.OnBarcode.com
Print EAN13 In Visual Basic .NET
Using Barcode encoder for Visual Studio .NET Control to generate, create EAN 13 image in .NET applications.
www.OnBarcode.com
Dim wholeFormGraphics As Graphics = _ Me.CreateGraphics( ) Dim buttonOnlyGraphics As Graphics = _ Button1.CreateGraphics( )
PDF417 Creation In VB.NET
Using Barcode encoder for .NET Control to generate, create PDF-417 2d barcode image in VS .NET applications.
www.OnBarcode.com
Creating UCC.EAN - 128 In Visual Basic .NET
Using Barcode drawer for .NET Control to generate, create EAN128 image in VS .NET applications.
www.OnBarcode.com
Some events, most notably the Paint event for forms and controls, provide access to a Graphics object through the event arguments.
2D Barcode Creation In Visual Basic .NET
Using Barcode printer for .NET framework Control to generate, create Matrix image in VS .NET applications.
www.OnBarcode.com
Intelligent Mail Generator In VB.NET
Using Barcode encoder for Visual Studio .NET Control to generate, create 4-State Customer Barcode image in VS .NET applications.
www.OnBarcode.com
Private Sub PictureBox1_Paint(ByVal sender As Object, _ ByVal e As System.Windows.Forms.PaintEventArgs) _ Handles PictureBox1.Paint Dim paintCanvas As Graphics = e.Graphics End Sub
QR Code Scanner In VS .NET
Using Barcode scanner for .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
QR Code JIS X 0510 Maker In .NET Framework
Using Barcode drawer for ASP.NET Control to generate, create Quick Response Code image in ASP.NET applications.
www.OnBarcode.com
You can also create a Graphics object that is unrelated to any existing display area by associating it to a bitmap.
Decode Barcode In .NET Framework
Using Barcode scanner for Visual Studio .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
PDF-417 2d Barcode Creation In VS .NET
Using Barcode encoder for .NET framework Control to generate, create PDF-417 2d barcode image in VS .NET applications.
www.OnBarcode.com
Dim trueBitmap As New Bitmap(50, 50) Dim canvas = Graphics.FromImage(trueBitmap)
Read GS1 - 12 In Java
Using Barcode decoder for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
Barcode Scanner In Visual Studio .NET
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
Remember, all changes made to the canvas instance will impact the trueBitmap image.
UPC - 13 Maker In None
Using Barcode creator for Font Control to generate, create European Article Number 13 image in Font applications.
www.OnBarcode.com
QR Code Drawer In Objective-C
Using Barcode encoder for iPhone Control to generate, create Quick Response Code image in iPhone applications.
www.OnBarcode.com
Disposing of Graphics Objects Properly
Making EAN-13 In None
Using Barcode encoder for Software Control to generate, create European Article Number 13 image in Software applications.
www.OnBarcode.com
GS1 - 13 Maker In Visual C#
Using Barcode printer for .NET Control to generate, create EAN13 image in .NET framework applications.
www.OnBarcode.com
When you are finished with a Graphics object that you create, you must dispose of it by calling its Dispose method. (This rule is true for many different GDI+ objects.) Don t keep it around for a rainy day because it won t be valid later. You must, must, must dispose of it when you are finished with it. If you don t, it could result in image corruption, memory usage issues, or worse yet, international armed conflict. So, please dispose of all Graphics objects properly.
Code 128 Code Set C Printer In None
Using Barcode encoder for Online Control to generate, create ANSI/AIM Code 128 image in Online applications.
www.OnBarcode.com
Recognizing Barcode In C#.NET
Using Barcode Control SDK for .NET framework Control to generate, create, read, scan barcode image in .NET applications.
www.OnBarcode.com
canvas.Dispose( )
If you create a Graphics object within an event, you really need to dispose of it before exiting that event handler. There is no guarantee that the Graphics object will still be valid in a later event. Besides, it s easy to re-create another Graphics object at any time.
Selecting a Canvas |
If you use a Graphics object that is passed to you from another part of the program (like that e.Graphics reference in the preceding Paint event handler), you should not dispose of it. Each creator is responsible for disposing of its own objects.
Choosing Pens and Brushes
A lot of graphics work involves drawing primitives: using lines, ellipses, rectangles, and other regular and irregular shapes to build up a final display. As in real life, you draw these primitives using a Pen object. For those primitives that result in a fillable or semifillable shape, a Brush object specifies the color or pattern to use in that filled area. GDI+ includes many predefined pens and brushes, or you can create your own.
Pens
Pens are line-drawing tools used with the drawing commands of a Graphics object. A basic pen has a solid color and a thickness.
' ----- A red pen five units wide. Dim redPen As New Pen(Color.Red, 5)
As with Graphics objects, any Pen you create using the New keyword must be disposed of properly when you are finished with it.
redPen.Dispose( )
Several predefined pens are made available through the System.Drawing.Pens class, all named by their color, as in Pens.Red. If you use one of these pens, you don t have to dispose of it. You can create a lot of interesting pens that vary by line styles, end decorations, and color variations. The following code generates the image displayed in Figure 18-2:
Private Sub PictureBox1_Paint(ByVal sender As Object, _ ByVal e As System.Windows.Forms.PaintEventArgs) _ Handles PictureBox1.Paint ' ----- Draw some fancy lines. Dim usePen As Pen ' ----- Blank out the background. e.Graphics.Clear(Color.White) ' ----- Draw a basic 1-pixel line using the title ' bar color. usePen = New Pen(SystemColors.ActiveCaption, 1) e.Graphics.DrawLine(usePen, 10, 10, 200, 10) usePen.Dispose( ) ' ----- Draw a thicker dashed line with arrow and ball ' end caps. Each dashed segment has a triangle end. usePen = New Pen(Color.FromName("Red"), 5) usePen.DashCap = Drawing2D.DashCap.Triangle
|
18: User Interface
usePen.StartCap = Drawing2D.LineCap.ArrowAnchor usePen.EndCap = Drawing2D.LineCap.RoundAnchor usePen.DashStyle = Drawing2D.DashStyle.Dash e.Graphics.DrawLine(usePen, 10, 30, 200, 30) usePen.Dispose( ) ' ----- A semitransparent black pen with three line ' parts, two thin and one thick. usePen = New Pen(Color.FromArgb(128, 0, 0, 0), 10) usePen.CompoundArray = _ New Single( ) {0.0, 0.1, 0.4, 0.5, 0.8, 1.0} e.Graphics.DrawLine(usePen, 10, 55, 200, 55) usePen.Dispose( ) End Sub
The code shows that there are a few different ways to specify a color, by either its predefined name (Color.White and SystemColors.ActiveCaption), a string name (using Color.FromName), or its Alpha-Red-Green-Blue value (Color.FromArgb). That last version lets you supply distinct values for the alpha blend (which sets the transparency level, from 0 for fully transparent to 255 for fully opaque), red, green, and blue components of the full color. Most of the pen-specific properties I demonstrated here are somewhat self-explanatory. As with most of GDI+, the mind-numbing amount of available features makes it impossible to completely document in a small chapter, let alone provide a good night s sleep for authors designing such chapters. I will simply refer you to the online documentation for the Pen class to get all of the luscious details.
Copyright © OnBarcode.com . All rights reserved.