Flash to Image Converter is a tool for converting frames of Shockwave Flash (SWF) to images. It is designed for running in MS-DOS command line mode. A MS-DOS interface supported application natively supports being called via a script. With a batch script, the application can process more than one SWF files in one command line.

A basic command for converting frames of a SWF to JPG images is as follows,
>swf2img.exe -in a.swf -out b.jpg .

Here is a simple guide about how to use Flash to Image Converter Command Line.

This command line converts frames of "a.swf" and save the converted JPG images with names of "b" followed by increasing continuous numbers, e.g., "b0001.jpg". The above command line can only converts one SWF file in one line. You can use these commands for converting all SWF files in the current directory.
>for %F in (*.swf) do "swf2img.exe" -in "%F" -out "%~dpnF.jpg" .

This command line will convert all SWF files (*.swf) in the current directory and save them using the name of the source SWF files with increasing numbers and extension name ".jpg" followed.

The following snapshot is of the batch conversion progress. You see that the two SWF files "a.swf" and "b.swf" are processed by the first command line displayed in the snapshot.

For more information, you can just type the command "swf2img" without any option in the MS-DOS command prompt interface.