From: "rmagick@..." <rmagick@...>
Date: 2007-07-17T02:40:00+09:00
Subject: Re: RMagick -- TIF to PDF

On Jul 16, 12:47 pm, paron <rphill...@engineer.co.summit.oh.us> wrote:
>
> image = image.negate.
>
>  If that isn't in there, the PDF comes out the negative of the TIF,
> but it seems like it ought to be unnecessary. Is it a bug, or did I do
> something silly?

I'm not a big TIFF user, but I think you're seeing an instance of the
condition discussed here:
http://www.imagemagick.org/discourse-server/viewtopic.php?f=2&t=8509&p=26135&hilit=photometric#p26135.

You can use the Image::Info#[]= method to define format-specific
options, assuming you have a version of ImageMagick that supports the
option. I'm not at a place where I can test it, but it woudl be
something like this

imgs = Magick::Image.read('C:/test.tif') {self["tiff",
"quantum:polarity"] = "min-is-black"}