This grayscale photo effect generator has useful features like:
- accepts JPG, GIF and PNG images;
- has several ways to transform the original colors into gray tones;
- offers great control of number of gray levels (you can even create black and white images);
- let you choose the quality level of JPG outputs;
- preserves alpha information (transparency) for GIF and PNG images.
Here you see some examples changing the grayscale criterion and number of gray tones:
You can use this new P2P utility at the Grayscale Image Generator page. I didn't announced it in the middle column of the main page, but there is a menu item to this tool in the "Utilities" section of the left side menu.