Online steganography service, hide message or file inside an image help

Settings Remark
Upload cover image The cover image is where a secret message or a secret file will be hidden in.
The cover image can be any of the following filetypes (max file size = 300 KB):
.bmp, .gif, .jpeg, .jpg, .png.
To avoid detection please use a cover image with plenty of fine details.

For example:
This simple black and white cartoon with few details is not good:

Cover image not good

The picture of a squirrel in the forrest with many fine details is good:

Cover image not good

Also less information hidden inside the cover image is better.