For anybody who wants the image file to save as a new file rather than replace the original:
Open the "Process image(s)" AppleScript block in the workflow
Find this line in the script:
save this_image in myPath
And insert the following to append the image filename with the target width (e.g. image.png becomes image-300.png when resized to 300px width):
-- append target width to file name
set oldDelim to AppleScript's text item delimiters
set AppleScript's text item delimiters to {"."}
set theExt to last text item of myPath
set AppleScript's text item delimiters to {"." & theExt}
set file_path_list to every text item of myPath
set AppleScript's text item delimiters to {"-" & target_width & "." & theExt}
set myPath to the file_path_list as string
set AppleScript's text item delimiters to oldDelim
