This article was created for my own purpose titled Creating Curved or Rounded Corners with GIMPa free, open source image editing and manipulation program.
The easiest way to create an image with rounded corners is to open your image,choose Select from the top,and choose Rounded Rectangle.You can adjust the 'Radius' to make the curves and also you can make concave curves also.Gimp will automatically create a rounded rectangle selection on top of your image.
When you choose the Rounded Rectangle tool under Selection, you will get the option to adjust the radius & for concave. This will be a trial and error process for you as there is no way to preview your radius selection.
Now choose Select -> Invert (Ctrl+I), then Edit -> Cut (Ctrl+X), then File -> Save As… (Ctrl+Shift+S) to delete the corner pieces. This eliminates the need to create a new image to paste into, which can be a time saver if you are working with many image.
After selecting the radius
At this point we are ready to design our XHTML with rounded corner images.