Graphics.DrawImage Method (Image, Point, Rectangle, GraphicsUnit, ImageAttributes, Graphics.DrawImageAbort)
Draws the specified portion of the specified Image at the specified location and with the specified size.
Assembly: System.Drawing (in System.Drawing.dll)
member DrawImage : image:Image * destPoints:Point * srcRect:Rectangle * srcUnit:GraphicsUnit * imageAttr:ImageAttributes * callback:Graphics.DrawImageAbort -> unit
- Type: System.Drawing.Rectangle
Rectangle structure that specifies the portion of the image object to draw.
- Type: System.Drawing.GraphicsUnit
Member of the GraphicsUnit enumeration that specifies the units of measure used by the srcRect parameter.
- Type: System.Drawing.Imaging.ImageAttributes
ImageAttributes that specifies recoloring and gamma information for the image object.
image is a null reference (Nothing in Visual Basic).
The destPoints parameter specifies three points of a parallelogram. The three PointF structures represent the upper-left, upper-right, and lower-left corners of the parallelogram. The fourth point is extrapolated from the first three to form a parallelogram.
The srcRect parameter specifies a rectangular portion of the image object to draw. This portion is scaled and sheared to fit inside the parallelogram specified by the destPoints parameter.
This overload with the callback parameter provides the means to stop the drawing of an image once it starts according to criteria determined by the application. For example, an application could start drawing a large image and the user might scroll the image off the screen, in which case the application could stop the drawing.
The following code example is designed for use with Windows Forms, and it requires PaintEventArgs e, which is a parameter of the Paint event handler. The code first defines a callback method for the Graphics.DrawImageAbort delegate; the definition is simplistic and merely tests to see whether the DrawImage method calls it with a null callBackData parameter. The main body of the example performs the following actions:
Creates an instance of the Graphics.DrawImageAbort callback method:
Creates an image from a JPEG file SampImag.jpg in the folder of the example.
Creates points that define a parallelogram in which to draw the image.
Creates a rectangle to select the portion of the image to draw.
Sets the graphics drawing unit to pixel.
Draws the original image to the screen.
Creates an additional parallelogram in which to draw an adjusted image.
Creates and sets the attributes of the adjusted image to have a larger-than-usual gamma value.
Draws the adjusted image to the screen.
For the original, unadjusted parallelogram, the position locates the image on the screen, and the size of the rectangle and the size and shape of the parallelogram determines the scaling and shearing of the drawn image.
Because this example uses an overload that does not pass a callBackData parameter, the Graphics.DrawImageAbort callback returns true, which causes the DrawImage method to end, and the exception-handling code included in the example prints out the exception text rather than drawing the image.