So I have a page with a bunch of images with largely varying sizes. Also the layout of the page is such that the images are all in the shape of square tiles, so just resizing will cause distorted images. What I've been doing previously is when users upload images, I resize and crop them appropriately and display the new image as the thumbnail and load full image when user clicks on it. However, I just realized this is an issue with SEO as google will crawl the thumbnails and stick the thumbnails on Google Images instead of the full images. Is there any way to show a cropped/resized image but have Google Image show the full image? I can do something with css using an enclosing div and overflow:hidden, but I'd imagine the performance on that would be pretty bad. Any suggestions?

Thanks!

PS. I saw this (Make google index the actual image not the thumbnail), but in my case I have users continuously uploading images, and the database of images is always changing and pretty big (thousands), so sitemap will be pretty unwieldy..