View Single Post
Old 27th June 2009, 11:00   #10  |  Link
reepa
Registered User
 
reepa's Avatar
 
Join Date: Aug 2003
Posts: 144
Quote:
no way to reconstruct details with upscaling. by downsizing pixels get discarded. you can do nothing to avoid that.
since pixels will be brutally deleted the best thing you can do is replace those pixels by interpolating the nearest ones (upscaling) with some complex interpolation function but subpixel details are gone forever. there is NO way to have them back.
If the high-resolution image doesn't have low-frequency details (say, if it's high-pass filtered), it can be downsampled without losing the high-frequency details. The details alias to low frequencies when downsampling. When upsampling later, the low frequencies "image" to high frequencies. By low-pass filtering the aliased details get removed and the "imaged", i.e. the original details remain.
reepa is offline   Reply With Quote