I have Psd image which is now 48x48 pixel and i like to change it to 128x128 without losing quality/resolution. How?
notes, the psd has multi layers
The question will be migrated to superuser.com soon. For the meantime:
It is not possible to enlarge a bitmap image without loss of quality. The data simply is not there. It's different from vector images where the image consists of geometric objects that can be enlarged indefinitely.
Photoshop's "Resize" dialog offers several interpolation filters with various results in quality. You can play around with them, but you will always suffer some loss in quality.
I'd say your best bet is to either to a normal resize and redraw the areas that are problematic or re-draw the entire image at the resolution you need. For bitmap images you can't put data where none existed before so resizing a 48 × 48 image to 128 × 128 won't look that good, naturally.
Icons are often drawn in vector graphics programs such as Illustrator and only exported to bitmaps. That way you retain all detail at multiple resolutions.