Downsizing images but retaining sharpness

[landyvlad]

I know that there are technical limitations to maintaining sharpness when reducing image size to very small.

For example taking an image from 1000X100 to 200x20. Naturally due to the small number of pixels to play with it's inevitable that it's impossible to maintain smooth curves/definition as there just isn't enough resolution to play with.

Having said that - can anyone suggest the optimal way to reduce image size but maintain the maximum possible sharpness?

1, For JPG
2. For PNG
3. AI and ESP files (going from a vector image to a small raster image for website use)

Any guidance gratefully appreciated.

[ricktas]

What software are you using?

If Photoshop: There are some good actions you can download from this set and install, that include sharpening actions : http://www.ausphotography.net.au/forum/showthread.php?139420-Photoshop-Actions-Collection

[ameerat42]

Work at a blown-up size on screen to check your results.

Apply only mild sharpening to the reduced size image.

If you haven't already tried it, give Filters-Other-High Pass a try.

But whichever sharpening you do, view the result at Full Size
(the magnifier, then Actual Pixels) to see how your sharpening
looks. Make sharpening your last step then toggle Ctrl-Z or use
History to switch between sharpened and unsharpened views.

Note that at different screen magnifications (scroll wheel to
reduce/enlarge the image) it will look alternately more and less
jagged as it interacts with the screen pixels. The Actual Pixels
is the critical size.

[fillum]

If you haven't already tried, you could experiment with the resampling options (in the PS Image Size dialog). Bicubic Sharper is the recommended method for image reduction but might be worth testing the others as well, particularly if you have a specific image type (e.g. text, logo, etc).


Cheers.

[ameerat42]

Lands. Looking back at your question, I see you asked about 3 different file types.
Treat the JPG and PNG files the same way, as they're both raster images. For the
vector images, get them down to the size you want before you rasterise them.

[landyvlad]

Sorry I forgot to respond here. I mean using something other than photoshop.