When I use Simple Scan to produce a pdf at 75dpi the resulting size is 84kB. When I use scanimage at the same resolution it produces a file size of 555kB.
As far as I understand it, you can create a PDF (basicaly a text oriented format) containing a picture in several ways. Also PDFs can be more or less compressed. Did you inspect the resulting documnets visualy? Is ther no difference at all between them?
There is no visual difference between the two. I am questioning the enormous difference in file size and how I can use scanimage to produce a file that is similar in size to that produced by Simple Scan.
Correct. It seems to accept the option but produces a PGM image. But when I produce a .tiff image and use “convert” to convert it to PDF. it’s still an enormous file.
The PDF specification allows the option of compressing an image using one of several different compression algorithms or none. It is up to the PDF creator; they just have different ways of dealing with images within a PDF.
FWIW, I’ve found from past experience that I can take a large (image-based) PDF and print to file, which then produces a noticeably smaller resulting PDF file, which I might then attach to an email. As the others mentioned already compression makes the difference here.
Many thanks to all of you. My solution has been to scan to .tiff with Scanimage giving me a high definition image, and to convert to .pdf with 75% compression for E-mail attachment. Scanimage offers a multitude of options not available in Simple Scan, one being a faster warm up time. It allows me to use it from inside a BaCon program to control the options.