Hi,

I'm building a website for a friend where some pictures need to be uploaded. The pictures need to get a watermark on them automatically after uploading (to prevent other people using them as their own), but the watermark placement cannot be 'static'; if I put it in the same place on each picture then it will obscure too much of the content in some pictures.

So I want to enable my friend to choose the location of the watermark (possibly even the size, but that's not really important at the moment) for each picture individually.
At the moment I just have a page with a FileUpload control that allows my friend to pick the image. It is uploaded when the OK button is pressed and the URL to the image is stored in a database. That's basically it.
Now I was thinking to make another page after the upload page where you can see the image you just uploaded and can drag a picture of the watermark (which will be a transparent PNG image, possibly GIF if PNG is not possible) around to place it. Once placed, the user could click an OK button and the watermark is copied onto the image.

So what I need is a way to drag an image (the watermark) over another image (the picture), as well as the possibility to retrieve the location of the watermark image (relative to the picture image) afterwards (so I can draw it onto the picture using GDI+).

Is there anything that allows me to do this? When I search for stuff related to dragging images all I find is drag and drop samples, where you take an arbitrary image file and drag it into the browser. That's not what I want; the watermark is always going to be the same image, and it will be on the image by default (in the center or something). The user should be able to move it (possibly outside the boundary of the image to completely hide it) but never completely remove it from the image and drag it somewhere else (no drag drop).

Any help?
Thanks!