Very nice indeed. this sw should be standard since years. I am surprised it comes so late and highly welcome it!

A few questions:

• Q.1: does the sw detect that the image contains a bitcoin key when entering the correct password even offline (e.g. by some header info or checksum after correct password entering), or is every image-password-combination a valid key? --> the latter would be better because:

• it would make the image even more difficult to brute-force! (you'd have to check with the blockchain each time you try a new password)
• it would provide powerful means against the "$5-wrench-attack": you can store two (or more) keys in one image via two (or more) different passwords and load different amounts on it. should you ever get attacked with a "$5-wrench", you give away your dummy key with a small amount of btc and plausibly deny existence of another key.

• Q.2: I understand that the privkey is stored in the 1 or 2 LSBs of each pixel's 8-bit RGB values, probably after XOR-ing with "sha1(password)"-bit-sequence or sth. like that. But this means that a *.png image would increase in size, compared to the original image, if the original *.png image contains sequences of pixels of identical colours, due to *.png's lossless compression (run lenght encoding). So the original image should preferably be an image that already contains some "noise" on the LSBs, do I understand correctly?
• Q.3: Does the SW support only individual keys or also HD keys with 12-to-24-word mnemonics acc to BIP32/39/44?