截取屏幕上未完全显示的“缩放”图像的屏幕截图

in my winform application i am trying to take screenshot of a image, and assign it to picturebox using DarwToBitmap() method. it works fine for me, but when i zoom the image and then take screen shot, in picturebox only part of image that was visible on screen is being shown. how can i capture screenshot of entire image, even if it is zoomed. ??in my winform application i am trying to take s