creating base64 encoded images
Heres a quick way to convert pictures into data-urls
openssl
step 1: convert image into base64 encoded text file
{ echo "=> data:image/png;base64,"; openssl enc -base64 -in input.png; } > image.b64
Step 2: Print data-url with no spaces
cat image.b64 | tr -d " \t\n\r"
Step 3: Copy/Paste data-url into gemtext