s(
    ((?#1) # Capture the entire tag beginning
     <img(?s:.+?) 
     src\s*=\s* # Optional space
     ((?#2)['"]) # Capture the delimiter
     ((?#3)(?s:.*?)) # Capture the URL
     \2 # Use whatever delimiter was used to start the URL
)
    { "$1$2" . resolveimg( $3 ) . $2 }gixe