App to Restore Large Images that were Shrunk?

[HoppaLong]

My image editing skill is limited to adding captions to pictures. Really, that's about
all I've ever done with a picture.

If I take several very large jpegs and reduce them in size, a simple mouse click will
restore them to their original size. No harm done.

My friend sent a collection of razor sharp small images taken with a multi-thousand
dollar camera. Their original size would have easily filled a standard sheet of copy
paper, if printed. They were reduced to fit several images on a single page. Restoring
them to their original size should be easy, but it's not.

As you enlarge these images you see jagged rows of densely packed pixels, not the
clarity you would expect. Because I helped him with a few complex computer problems,
he thinks I can explain or fix the problem with these images. Maybe someone at this
forum can provide a solution.

I'm guessing it might be possible to restore the original clarity of these images with the
right app. Is there some newbie friendly freeware that could do the job? If expert level
software is required like Adobe Photoshop I'm out of luck. A simple app with a name like
"Blowup Your Images" would be perfect.

[jumper]

Your friend's camera might be capable of taking razor-sharp large pictures, but they were saved in a low quality mode (small size in this case). Regular JPEG is a lossy-compression format. The clarity of the original images is lost and gone forever.

> If I take several very large jpegs and reduce them in size, a simple mouse click will

restore them to their original size. No harm done.

You must first have large, high quality images, and then the app must support undo. If you resave the files and the power fails or the system crashes before clicking "undo", the original quality is gone.

[dencorso]

Even when using non-lossy formats, like  GIF, TIFF or PNG, when a image is shrunk, there'll be less pixels per feature than originally, so that resolution is therefore lost. For enlarging, one may even use refined methods of pixel interpolation to restore some of the lost resolution, but the results will still be less satisfactory than the original, non-manipulated image.

[HoppaLong]

Yes, I understand. Thank you jumper and dencorso.

My friend was not the owner of that expensive camera. The pictures were taken by
a professional. They were reduced in size for a trade magazine.

He has a few full size framed prints hanging on his office wall. That's why he was
puzzled when the smaller images couldn't be enlarged.

[Tripredacus]

When a raster image is shrunk and then saved, the now unused data is deleted from the file. This is why you can't resize then afterwards. There are *some* cases where the information is retained but typically unavailable. For example, Program1 can read this data and the image can be resized in Program1 (or only if in the native format) but cannot by other programs. A practical example of this behaviour is with Fireworks PNG files (as a vector format) can be re-opened and changed in Fireworks but not by other PNG capable programs like Paint or Photoshop.

Image (like video) upscaling does exist and is described here: http://www.cs.huji.ac.il/~raananf/projects/lss_upscale/paper.pdf

But since you are relying on a program to enlarge the image for you, results may vary. For use on a webpage it may not be ideal because you can see the blending effect up close. Same would be for photo printing, but poster printing may be acceptable as long as you don't get to close.

However, some people are more sensitive to image quality than others. An example is that some can live with connecting a VCR to an HD TV but others cannot stand it and would insist on using a VCR on an SD TV or maybe using an upscaler on an HD TV.