img = doc:LoadJPEGImage(filename)
doc:LoadJPEGImage() loads an external JPEG image file.
When doc:LoadJPEGImage() succeeds, it returns the handle of an image object. Otherwise, it returns Nil and the error handler is called.
#HPDF_INVALID_DOCUMENT - An invalid document handle was set.
#HPDF_FAILED_TO_ALLOC_MEM - Memory allocation failed.
#HPDF_UNSUPPORTED_JPEG_FORMAT - Unsupported JPEG image format.