manuals in pdf (resolution, compression)

From: Paul Williams <paul_at_frixxon.co.uk>
Date: Sat Jun 26 17:05:30 2004

Tom Owad wrote:
>
> I was doing 150dpi greyscale jpegs. I've changed to 400dpi 1bpp tiffs,
> and now I'm ending up with each page about 700K... (scan as greyscale
> tiff (unknown compression), convert to 1-bit with lzw compression, save
> as pdf in Photoshop).

You need to scan at 1bpp, not grayscale. When you are converting from
grayscale to 1bpp, you are probably getting dithering (a pseudo-random
scattering of black and white pixels) in order to approximate the
original grays at the edges of characters. This dithering will ruin the
achievable compression in G4, which is a fax algorithm optimised for
runs of white and black pixels.
Received on Sat Jun 26 2004 - 17:05:30 BST