Scale transformation of images

[Eli Zaretskii]

If I insert an image into a buffer with insert-image, and then position point 
on the image and press '-' to make it smaller, the scale factors I see in the 
transform matrix are greater than 1.  This is because image_set_size does this:

   double xscale = img->width / (double) width;

and similarly for yscale.  Shouldn't we divide width by img->width instead?