What is preview doing to make jpegs look better?

I got the hp combo photoscanner printer that came with the imac last year and the scanner makes pictures look kind of rough but preview compensates somehow. How do I make the preview changes perminent? Can it be saved? Or is there something I can do in iphoto or photoshop to hide the grain?

Could it just be that the image is smaller in preview? I really don't know, that is just the first thing that popped in my head.

Nope, because it first comes up looking a bit grainy and spotty and then it adjusts to a very clean image. How can I keep it clean?

Simply put, Preview has no image enhancement or corrective capabilities. It is an image viewer, not an image editor.

Devilboy, that is not true with 10.5. Preview is actually quite robust now...




To answer the original question, preview is post-processing the image. It is anti-aliasing to give the appearance of a smoother image. The only way to keep that post processed image is to take a screen grab, since the image you are seeing doesn't actually exist - if you were to simply SaveAs, you would get the original, un-post-processed image.

If it's a large image, Preview will first open it in sort of "low res" mode, before showing the actual image after few milliseconds. This looks as though it's taking a "jagged" image and smoothing it out, but it's really just Preview loading in the image's full resolution... it has no effect on the image's real quality.

Aptmunich said:

If it's a large image, Preview will first open it in sort of "low res" mode, before showing the actual image after few milliseconds. This looks as though it's taking a "jagged" image and smoothing it out, but it's really just Preview loading in the image's full resolution... it has no effect on the image's real quality.

Click to expand...

This staged viewing is done for performance reasons. It initially loads it at a lower resolution so that you can flip through images extremely quickly.