Increase Photo size w/o losing quality

[lcosan]

Hi, how can I increase the size of an image w/o losing quality. I have a stock photo that I want to use for a header but when I increase the size, I lose the quality. I have photoshop 7. Any tips?

Thanks

[stewball]

You can't. Raster images (bmp, jpg, raw, png, etc) store pixel data in terms of colour per pixel. So, when you try to enlarge it the data per pixel is distributed according to the number of pixels relative to the size of the resized image. In other words the logical pixels get bigger, and so sharpness is lost.

[uncaff]

You might want to take a look at this web page which discusses several methods of enlarging photos in PS with minimal quality loss:

http://www.imaging-resource.com/SOFT/GF/GF.HTM

It also discusses a PS plug-in called Genuine Fractals (rather pricey, but with good reviews) which uses an algorithm to divorce image size from pixel resolution. The Genuine Fractals website - linked at the above page - offers a free demo.

Hope this helps.