Forum Moderators: not2easy
example 1024x768 to 1280 x 768 or 1920 x 1200
I can say I got Photoshop CS, but not a expert.
You need enough original pixel data to make the pixels for your larger image.
Resizing and cropping images are basic commands in Photoshop... no expertise needed, just read the navigation tabs. As for the quality changes...
If you are cropping the image, you'll have no issue. If you're sizing down the image, you won't have too much of an issue. If you are stretching/increasing the image size, you will have a big issue. More accurately, you can't stretch an image without it looking stretched, period. You can't increase the size of an image without adding fake pixels, period. Either of those tactics are not what you want to be doing if you have any concern for image quality. If you have a 800x600 image, and want it to be 1600x1200... well then, you have to throw that one out and make a new image at 1600x1200.
The other thing is that a lot of people say they want "no loss of quality" but the fact is that 99% of people will not notice the difference between a JPEG saved at the highest quality ("12" in photoshop) and one saved at "9". Quality loss is not important... what's important is whether it looks good enough for what you're using it for. 30 foot billboards look great when you're driving by, but horrible when you're 2 feet away from them... it doesn't mean we need higher quality billboards; it means we need to stop standing 2 feet away from them.