I have an html form where users insert an image (input). My users may be not advanced users, so they may want to insert many different types of image format. However, I only want the user to send jpg/gif/png files. One option is just block other file types, however, I was wandering if I could convert the files in the client side (I don't want to send a very large file, and convert it on the server). Therefore, the only way I can think of is using javacript.

So, does any one know how to make image format conversions in javascript? And put this image result as the value of an html:input?

Thanks!