How to find images in Google as per specific parametres

One can search for an image as per the image size or as per the below defined parametres
imagesize:WIDTHxHEIGHT
imagesize:256×256 filetype:png gimp
imagesize:1280×1024 filetype:jpg design
One even has an option of searching the image as per image size. One can set image size in pixels 256×256 or 1920×1200. You can also specify required image type: png, jpg or gif.
imagesize:1024x768 nature ] finds 640px x 480px images related to nature.