imageList.Draw doesn't draw with different size?

The ImageList has a method named "Draw":

imageList.Draw(graphics, bounds.X, bounds.Y, bounds.Width, bounds.Height, imgIndex);

I use this method to draw an image on a graphics object of a PrintDocument. When using the original image size (16 x 16 pixels), the image is drawn correct. If however, I change the bounds size, n开发者_如何学运维othing is drawn. Even changing the size to 32 x 32 (double size) has no effect. Nothing is drawn. I need to change the drawn size because of the different dpi ... Where am I gong wrong ?

Edit: The solution seems to be simply to use the g.DrawImage method instead. Why imageList.Draw() doesn't draw is still a mistery to me ...

g.DrawImage(imageList.Images[imgIndex], bounds);

ImageList.Draw() is a bit unusual, it takes advantage of the built-in support that the native image list code inside of Windows has for rendering an image in the list. This is an optimization, it avoids the cost of converting the internal image as stored in the native image list back to a managed Image object.

One side-effect however is that this drawing happens without regard for any of the transforms that were applied to the Graphics object. A 16x16 image in the list is going to be rendered as 16x16 pixels on paper. Which is indeed a bit hard to find back, printers have very high resolution (600 dots per inch is typical), that image turns into a decimal point.

Image lists were really meant to be the source of images for the TreeView and ListView controls, it is not a good general purpose collection object for images. Like a List<Image>. Your workaround is good, the Image property converts the internal bitmap back to a managed Image, Graphics.DrawImage() will then scale it appropriately to get a size on paper that's close to the size on the screen. However with the graininess you get from making an image 6 times larger. Note that you should Dispose() that object.