Enhancements:

[zenglian]

1. Remember the folder for "Browse..." button.
2. Preview the merged image.
3. Mutilple columns * rows instead of vertical and horizontal.
4. Merge all images into 1 file (detecting duplicate file names under different folders).
5. Allow user to unselect images in a folder (show a list/tree for selection).
6. Generate a seprate .css file (besides the html file).
7. Post-processing, which means replacing image references to sprite.
   (1) Parse web files (html, aspx, asp, cshtml, vbhtml, jsp, jspx etc...) for image references
   (2) search the images
   (3) merge them, generate css file
   (4) replace all references to the css.file
   Much work ... :)