How to: Create Thumbnail Images
A thumbnail image is a small version of an image. You can create a thumbnail image by calling the GetThumbnailImage method of an Image object.
Example
The following example constructs an Image object from a JPG file. The original image has a width of 640 pixels and a height of 479 pixels. The code creates a thumbnail image that has a width of 100 pixels and a height of 100 pixels.
The following illustration shows the thumbnail image.
.png "Thumbnail Image")
Note
In this example, a callback method is declared, but never used. This supports all versions of GDI+.
Public Function ThumbnailCallback() As Boolean
Return True
End Function
Private Sub GetThumbnail(ByVal e As PaintEventArgs)
Dim callback As New Image.GetThumbnailImageAbort(AddressOf ThumbnailCallback)
Dim image As Image = New Bitmap("c:\FakePhoto.jpg")
Dim pThumbnail As Image = image.GetThumbnailImage(100, 100, callback, New IntPtr())
e.Graphics.DrawImage(pThumbnail, 10, 10, pThumbnail.Width, pThumbnail.Height)
End Sub
public bool ThumbnailCallback() {
return true;
}
private void GetThumbnail(PaintEventArgs e)
{
Image.GetThumbnailImageAbort callback =
new Image.GetThumbnailImageAbort(ThumbnailCallback);
Image image = new Bitmap(@"c:\FakePhoto.jpg");
Image pThumbnail = image.GetThumbnailImage(100, 100, callback, new
IntPtr());
e.Graphics.DrawImage(
pThumbnail,
10,
10,
pThumbnail.Width,
pThumbnail.Height);
}
Compiling the Code
The preceding example is designed for use with Windows Forms, and it requires PaintEventArgs e, which is a parameter of the Paint event handler. To run the example, follow these steps:
Create a new Windows Forms application.
Add the example code to the form.
Create a handler for the form's Paint event
In the Paint handler, call the GetThumbnail method and pass e for PaintEventArgs.
Find an image file that you want to make a thumbnail of.
In the GetThumbnail method, specify the path and file name to your image.
Press F5 to run the example.
A 100 by 100 thumbnail image appears on the form.