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June 2005

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2005.06.20 10:19 "Invert-problem", by Matthias Lach
2005.06.20 11:47 "Re: Invert-problem", by Michel Salvagniac
2005.06.20 15:52 "Re: Invert-problem", by Bob Friesenhahn

2005.06.20 15:52 "Re: Invert-problem", by Bob Friesenhahn

On Mon, 20 Jun 2005, Matthias Lach wrote:
> 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 
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.

Bob Friesenhahn,
GraphicsMagick Maintainer,