GFXMENU: Image scaling

[Towheed Mohammed]

Scaling down an image does not work as intended.  The image only scales down 
when it's corners touches the respective corner of the screen.

Using a 320x320 image and setting the image component's properties thus:
        + image {
            top = 100%-20
            left = 100%-20
            width = 20
            height = 20
            theme_dir = "/usr/share/grub/themes/demo/images/"
            file = "gnu320.png"
        }

scales the image to 20x20 as expected.  See screenshot: bug-image-scaling-1.png

However, using the same image, and setting the image component's properties 
thus:
        + image {
            top = 80%
            left = 80%
            width = 20
            height = 20
            theme_dir = "/usr/share/grub/themes/demo/images/"
            file = "gnu320.png"
        }
 
does not scale the image to 20x20.  See screenshot: bug-image-scaling-2.png.  
The image is actually scaled to fit the area between 80% and 100% of the 
screen's dimension.

This shows that the image is not scaled if it's edges does not touch the 
respective screen boundaries:
        + image {
            top = 0
            left = 368
            width = 20
            height = 20
            theme_dir = "/usr/share/grub/themes/demo/images/"
            file = "gnu320.png"
        }


See screenshot: bug-image-scaling-3.png

If the same image is used as an icon for the menu items, it scales properly.  
See screenshot: icon-scaling-1.png

bug-image-scaling-1.png
Description: PNG image

bug-image-scaling-3.png
Description: PNG image

bug-image-scaling-2.png
Description: PNG image

icon-scaling-1.png
Description: PNG image