First you need to verify its the identical picture. One sunflower looks a lot like another.
Visipics is free and will compare pixel by pixel. You can even adjust how sensitive it is. I use it to weed out dups in my photo collection.
For your purposes set the slider to strict. That requires a perfect match. Basic will incorrectly flag similar pics as dups.
http://www.visipics.info/index.php?title=Main_Page
It’s the same pic. A quick look at the pics (see the linked sites in my OP) will show them to be the same pic.
However, I can’t do a software match as you suggest because they cropped it and threw a banner up in the front of part of the pic.
Zev Steinhardt
I suggest clown porn.
Look at the damn links, will ya?
It’s clearly and unambiguously the same picture. Yes, lots of sunflowers look alike, but the pictures are clearly the same. The leaf or blade of grass sticking up through the petals on the right of the flower; the shapes and colors of the out-of-focus background; the placement of a small, brighter yellow spots in the dark center of the flower; the identical arrangement of every single petal. There is no reasonable evaluation that could conclude anything but that they are the same image.
ETA:
Here are direct links to the two images:
I suspect you could crop the visible part from each and it would be enough to compare with that site. But its obviously the same pic.
Otara
By the way, Zev, how did you find the stolen pics? Just stumble across them, or were you searching?
You mean you’ll begin registering them. In a Berne country, saying that you are “copyrighting” something has no meaning because an original, creative work is protected by copyright law as soon as it is fixed in a perceivable medium.
Firefox has an extension called “Who Stole My Pictures” where it searches through several image search engines for similar pics – including Google.
Zev Steinhardt
Yep, that’s what I meant. 
Zev Steinhardt
Or replace it with a picture that isn’t as nice–like a big hairy toe, or a rusted nail or a crumpled tissue.
I’m sure the site isn’t hot-linking to the photo. They’ve downloaded it and put it on their server.
Re-read post #9. One site apparently is.
For what it’s worth, this book has a lot of great legal advice on what you can do to prevent someone from stealing your pictures (and “prevent” here really means getting them to stop and/or extracting the largest possible amount of financial restitution).
It’s a must-read for anyone who’s posting their photos to the net, IMHO. At the very least, you should see if the library has it.
Correct. The site I linked to isn’t hotlinking. Another site that stole a pic of mine is doing so.
Zev Steinhardt
You should also consider putting your copyright notice as metadata inside of the image file itself (better than a watermark because it’s invisible and some people don’t even know it’s there). If they are too stupid to scrub it, which they probably are, then you have an ironclad case against them.
That also means writing to the major search engines. If you can convince them you are the owner, the best return is they derank the site and remove it from search results, effectively killing off the site. Also consider writing to the domain registry and the web host.
Although the attitude of the OP is quite defensible, personally I’m with beowulff on this. I love it when I see my photos used - and I’m amazed at the variety of ways they have been pressed into service. (Everything from a French human rights NGO to a business PPT to an article on kids’ nutrition to free “wallpaper” that you can download for your cellphone.)
I license my photos under Creative Commons, so no one is “stealing” from me. However, I always assume that since I’ve been able to find my photos on the web by searching on my name, there are a number of other places that have taken my photos and didn’t bother to credit them. While I’d be interested to see what they’ve used the pictures for, I don’t really mind.
I’m with the OP. I’ve always asked for my photos to be taken down, or for compensation. For non-profits we can often work out a photo credit if I approve of their work. For commercial sites, heck no. I’m not putting paid photographers out of work because these folks are too cheap to buy an image or take one themselves.
The point is that it’s supposed to be the creator’s decision whether to allow uses or not.
I used to work for a major film studio in their Copyright & Trademark Department.
In the USA, there is some recourse, but outside of the US it gets more difficult - every country has different laws and you have register work in that country to be protected. We used to register images and logos from films and characters in almost every country in the world. It was a pricey venture and took a lot of research - you would often have to get it notarized, sent to a local consulate, then to the main consulate in the USA, then to the specific department in that country and then wait for the paperwork to be completed. If it were infringed, you would then need to find a lawyer in that country to file a complaint. Our department had about 7 people working full time on this, and we could barely keep up with the bare minimum of marks and copyrights on major characters and films. We then had legal temps who would go through potential infringements. It was pretty much a never-ending battle. However, if you do nothing you are basically saying you don’t care - so you did the right thing by sending that email. It won’t help much in your case, but that will make a future case in the USA stronger by showing you actively go after any infringement you see and can prove (in your email or letter) that you have done so in the past. This shows intent to keep your rights.
And yes, you should at least put the words “Copyright 2012” and your name on every photo. Some people have less than stellar Photoshop skills and might skip over that photo because of it or at least feel like a thief when they take it and use it. In your case, all they had to do was to fiddle with the photo a bit - make it larger/smaller, flip it, alter the color, add a few leaves or whatever, and you probably would never have known.
BTW, this is yet another warning about posting anything on the internet - once it is out there, you never know who is going to use it for what. That sexy photo you used to get a date on Craig’s list will most certainly show up on someone’s porn site in the Ukraine - just sayin’ that people will grab what they want and use it however they want and rarely will you have any recourse whatsoever.
