09-18-2013 05:57 AM - edited 09-18-2013 07:13 AM
You can't predetermine the file size. That depends on how well the processing can compress the file.
You have an image that is 50 x 50, that is 2500 pixels. Each pixel requires (I think) 4 bytes, so an uncompressed 50 x 50 image should take 10 Kb. Compressed should be smaller.
Try this with your standard desktop image manipulation software - even standard Microsoft paint will do this.