Tell me how to enlargew in sense of dimensions for printing purposes without losing its quality i.e., pixels should not be cracked.

It's impossible

If you have a set resolution on a picture, you can blow it up, but what you are doing is expanding those pixels. You would have to add pixels to keep a clean look.

Like henry said, it's impossible.

It is impossible to maintain the quality, but depending on the initial quality of the image and by how much you want to blow it up by, you may not notice the loss. Eg, if you have a high quality image that you want to make 10% bigger you could probably get away with it.

Depending on the image you can sometimes blow up to say 400% instead of 200%, use sharpen filters, then reduce to 200% again and sharpen. You can't create detail that was never captured so scaling up will never look great but it may look acceptable.

You could use a professional image interpolation program. It wouldn't be lossless, but it would generally yield better results than just resizing it with Paint or Photoshop.

I think the only way to do this is to use I believe the term is a "vector" program. It works differently than a pixel program like say photoshop. Photoshop uses a bunch of pixels and a vector program used mathematics instead to determine where things are. So basically with a vector program you can make something and print it in any size and it will not have any loss.

Someone please correct me if that is not what it is called, it has been a long time since I read about it.

I'm afraid you're off, johniman. Vector and bitmap images are entirely different and not related to one another.

As stated before, the bottom line is, there is no way to enlarge a bitmap image without losing quality. There are programs and plugins out there that use fractal algorithms to better guess new pixels, but they still aren't 100% crisp.

If you absolutely have to enlarge an image, I wouldn't enlarge it to more than twice the original size. One little trick I use is to dupe the image onto a new layer, sharpen it, then knock down the opacity to around 50%. This makes the image a tiny bit crispier without that stair-stepped, hard-edged "I've been sharpened in Photoshop" look

Ok, I wasn't 100% sure. I forgot to mention that this won't help you with an existing bitmap image. You would have to create the image or graphic in a vector program. So if you could create a logo or something in the program it would work but something like a photograph would have to be done in a bitmap program. I tried.

Yea it is impossible to do what you are saying.

the bottom line is, if the original picture itself is a very high pixel one, you won't need to worry to blow it up high. still, it's impossible to enlarge a low pixel pics.

as high as you want

Try to use Topaz.

You can't expand an image without losing it's sharpness.
Enlarging an image just enlarges every single pixel, so your bound to loose out on the quality. Slight enlargements are fine, because most of the time you can never tell the difference.

Trace it with photoshop and expand it.

I did read somewhere (photography mag) that enlarging/reducing in photoshop is better when you do it in smaller increments - ie 1% at a time.

There are other retail apps/plugins for photoshop that work better.
I'm sure a quick Google will surface a few options.

Then again... what does Photoshops Smart Objects work like? I thought that was good for resizing things...?

This may be of help to you. Just look on Google for "photo interpolation".

the quality wont be 100% after you expand the image.

Good point

As far as third party software, I have had really good results with "Blow Up" from Alienskin, it is a photoshop plugin. They claim to be able to quadruple the original image size without any loss of sharpening. This holds more true when the original image is perfectly sharp, as all the small imperfections are magnified. I use this plug all the time for surfing pictures and it makes my dismal 2.0 megapixel shots look reasonable

I think using BMP files over JPEG will certainly increase quality, but of course that would mean a bigger file.