I've written an image watermarking plugin for my client, that watermarks all the product details image (but not those image in the thumbnail view in category). The works were based on http://www.codeproject.com/Articles/2927/Creating-a-Watermarked-Photograph-with-GDI-for-NET for the watermarking part. Then I also created a Handler that applies the watermark image dynamically based on certain condition. :)
I am also trying to develop a watermarking plugin based on that article. I need some suggestions about this:
1. How should I save the watermarked image? Should I overwrite the previous image? If so it may not be possible to retrieve the original image (If user thinks to disable the watermark).
2. Once an image is watermarked, definitely no need to watermark the image again. How can I detect it and how the image caching is applicable?
May be too much questions, but it would be helpful if you suggest me.