It's hard to tell since you give no details (a little ironic, that) but the clarity of a graphic posted here has nothing to do with how it's uploaded. It's the responsibility of the original poster to make sure they're posting a clear image.
One thing that might be causing your problem is that many browsers will automatically resize an image to fit within your browser window if the image is too large to fit. If the image has fine detail then the resizing algorithm used by the browser can cause some of the lines to disappear or other details to be lost. You can usually make your browser show you a full-size version by clicking on the image.
Sometimes you have to click on the pic to get it to blow up to full size
so you can see the detail.
Other times you have to copy the picture or save to hard drive, then
open with your favorite picture viewer.