$ openssl
OpenSSL> base64 -in "test.png" -out "test.txt"

openssl base64 -in test.png -out test.txt

echo -n "data:image/png;base64,$(cat test.png | base64 | tr -d '\r\n')" > test.txt

sips -s format jpeg test.png --out test.jpg

sips -s format bmp test.jpg --out test.bmp