Question

Is it possible to have an image without watermark on my page and when people try to download the image by accessing the right click menu and “save image as”. To let them download an image with the watermark applied to it?

Answer 1

So apparently you can check which mouse button was pressed in a mousedown event handler and if it was the right button change the source of the image:

​$('img').on('mousedown', function (event) {
    if (event.which == 3) {
        this.src = this.src.replace('.jpg', '_watermark.jpg');
    }
});​​​​​​​​​

Here is a demo: http://jsfiddle.net/s6A9m/