Upload images question; limit file size

[EnmnM]

Using

Thanks to this community, I created a button that lets the user upload an image into an image field:

this.getField("image").buttonImportIcon();

I also learned that it is not possible to "reset" the image field; I need to link the "reset" button to a blank image. (This is a major annoyance.)

My last question is: how do I ensure that the user does not upload a large (greater than 300 kb) image? I can't figure out the code for this.

Thanks.