Hens Zimmerman's  ToolBook - JPG Filter

Here is a brief description from Hens's release notes:

The TBJPG.DLL is a file-converter. It converts a JPEG to a BMP in a single call. As a ToolBook-developer you can add this DLL to your files and re-distribute it with applications you create.

The primary function is TransferJPEG.  After linking the DLL, the call 
TransferJPEG(jpgFile, bmpFile) 
takes an existing JPG-file (the first parameter, a regular TB-string) and creates the equivalent Windows BMP (bitmap), which is specified in the second parameter. This, too, is a regular TB-string.