2005.06.20 15:52 "Re: [Tiff] Invert-problem", by Bob Friesenhahn
ist me again - and i have still a problem saving my file.
i opend a fax g-3 tiff with LibTif for Delphi (D7).
I open it as 32 bit bitmap and can work and manipulate it if i like ot save it i need to convert it back into 1-bit because all other formats make the outputfile looks jolted.
But - no matter what bit-format i choose, all output is invertet - and i cant find the reason why.
The problem is likely with using the wrong photometric. The choices available are PHOTOMETRIC_MINISBLACK and PHOTOMETRIC_MINISWHITE. Grayscale images will usually be PHOTOMETRIC_MINISBLACK since this is how computer display systems work, but since paper is white, FAX uses PHOTOMETRIC_MINISWHITE. So you should set the photometric to
PHOTOMETRIC_MINISWHITE and make sure that the sense of the bits is inverted to reflect that. In other words, a set bit indicates a black pixel when the photometric is PHOTOMETRIC_MINISWHITE.
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/