问题
I need to enlarge the image downloaded without affecting its clarity.but when resized its clarity has gone.Can any one help?
回答1:
Given the context, by clarity I assume you mean visual appearance. You want your upscaled image, again I believe you are dealing with upscaling and not downscaling (it is not specified in your problem), to look visually good. We actually can magically create detail, but probably not a perfect one. There are techniques for specifically working with pixelated images, hqx or http://research.microsoft.com/en-us/um/people/kopf/pixelart/paper/pixel.pdf for instance. Since that is not clear from your description either, I'm simply assuming you have images of any kind.
With these considerations, you have yet to describe what you tried. Let me guess you tried a nearest neighbor interpolation, so you get something like:
There are other common types of interpolation. Like bicubic, Lanczos or something more modern like ICBI or http://www.cs.huji.ac.il/~raananf/projects/lss_upscale/paper.pdf. Consider the first three of those, we get the respective results:
It may be a little hard to visualize the differences among these last three, but if you zoom into the actual images then you will be able to notice them. ICBI gives sharpest edges in this case.
回答2:
Image resizing will always affect clarity, unless you downloaded a vector graphics image. See if the image has a vector graphics format, and if so, download that.
Failing that, you could try to see if larger image sizes are available, as generally shrinking hurts the image quality less than increasing.
来源：https://stackoverflow.com/questions/13688169/enlarging-image-without-affecting-clarity