Graphics.FromHdc Method

Definition

Namespace:

System.Drawing

Assembly:

System.Drawing.Common.dll

Creates a new Graphics from the specified handle to a device context.

Overloads

FromHdc(IntPtr, IntPtr)	Creates a new Graphics from the specified handle to a device context and handle to a device.
FromHdc(IntPtr)	Creates a new Graphics from the specified handle to a device context.

FromHdc(IntPtr, IntPtr)

Source:

Graphics.cs

Creates a new Graphics from the specified handle to a device context and handle to a device.

C#

public static System.Drawing.Graphics FromHdc(IntPtr hdc, IntPtr hdevice);

Parameters

hdc

IntPtr

Handle to a device context.

hdevice

IntPtr

Handle to a device.

Returns

Graphics

This method returns a new Graphics for the specified device context and device.

Remarks

You should always call the Dispose method to release the Graphics and related resources created by the FromHdc method.

Even if the display device has an associated ICM color profile, GDI+ will not use that profile by default. To enable ICM for a Graphics, construct the Graphics from an HDC after you pass the HDC (and ICM_ON) to the SetICMMode function. Then any drawing done by the Graphics will be adjusted according to the ICM profile associated with the display device. Enabling ICM will result in slower performance.

The state of the device context (mapping mode, logical unit, and the like) at the time you call FromHdc can affect rendering done by the Graphics.

The device handle is typically used to query specific printer capabilities.

FromHdc(IntPtr)

Source:

Graphics.cs

Creates a new Graphics from the specified handle to a device context.

C#

public static System.Drawing.Graphics FromHdc(IntPtr hdc);

Parameters

hdc

IntPtr

Handle to a device context.

Returns

Graphics

This method returns a new Graphics for the specified device context.

Examples

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 performs the following action:

• Creates an internal pointer type variable hdc and sets it to the handle to the device context of the graphics object of the form.

• Creates a new graphics object using hdc.

• Draws a rectangle with the new graphics object (on the screen).

• Releases the new graphics object using hdc.

C#

private void FromHdcHdc(PaintEventArgs e)
{
    // Get handle to device context.
    IntPtr hdc = e.Graphics.GetHdc();

    // Create new graphics object using handle to device context.
    Graphics newGraphics = Graphics.FromHdc(hdc);

    // Draw rectangle to screen.
    newGraphics.DrawRectangle(new Pen(Color.Red, 3), 0, 0, 200, 100);

    // Release handle to device context and dispose of the      // Graphics object
    e.Graphics.ReleaseHdc(hdc);
    newGraphics.Dispose();
}

Remarks

You should always call the Dispose method to release the Graphics and related resources created by the FromHdc method.

Even if the display device has an associated ICM color profile, GDI+ will not use that profile by default. To enable ICM for a Graphics, construct the Graphics from an HDC after you pass the HDC (and ICM_ON) to the SetICMMode function. Then any drawing done by the Graphics will be adjusted according to the ICM profile associated with the display device. Enabling ICM will result in slower performance.

The state of the device context (mapping mode, logical unit, and the like) at the time you call FromHdc can affect rendering done by the Graphics.