GDI+ FromImage, FromHdc, and FromHwnd Methods in VB.NET

In this article I will explain about The FromImage, FromHdc, and FromHwnd Methods in GDI+.
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An application can use Graphics class members to get a Graphics object. The Graphics class provides three methods to create a Graphics object: FromHwnd, FromHdc, and FromImage.

FromImage takes and Image object as input parameter and returns a Graphics object. The following code snippet creates a Graphics object from an Image object. One a Graphics object has been created, you can call its members.


        Dim img As Image = Image.FromFile("Rose.jpg")
        Dim g As Graphics = Graphics.FromImage(img)

        ' Do something
        g.Dispose()

Note: Make sure you call the Dispose method of the Graphics object when you're finished with it.

FromHdc creates a Graphics object from a window handle to a device context. The following code snippet shows an example in which FromHdc takes one parameter, of type IntPtr.


        Dim hdc As IntPtr = e.Graphics.GetHdc()
        Dim g As Graphics = Graphics.FromHdc(hdc)

        ' Do something
        e.Graphics.ReleaseHdc(hdc)
        g.Dispose()

Note: You need to call the ReleaseHdc method to release resource allocated by a window handle to a device context, and also make sure you call the Dispose method of the Graphics object when you're finished with it.

FromHwnd returns a Graphics object for a form. The following method takes a window handle.

Dim g As Graphics = Graphics.FromHwnd(Me.Handle)

To draw on a form, an application can pass this handle. One an application has a Graphics object, it can call any Graphics class method to draw graphics object.

Conclusion

Hope the article would have helped you in understanding The FromImage, FromHdc, and FromHwnd Methods in GDI+. Read other articles on GDI+ on the website.

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