Change to --export-dpi functionality
Where the user specifies --export-dpi in a command line along with one or both of --export-width or --export-height, set this value into the pHYs chunk of the PNG file.
Where the user specifies --export-dpi in a command line along with one or both of --export-width or --export-height, set this value into the pHYs chunk of the PNG file.