2004.01.22 02:13 "Re: [Tiff] change fax resolution", by Joris Van Damme

1. Create the PNG image of 1728x2280
2. Reduce the height to 50%, so I get a PNG image of 1728x1140 using something like ImageMagick
3. Save the tiff image with the TIFFTAG_YRESOLUTION set to 100

Is this the correct way of do it?

Yes, it is.

Alternatively, you could do the resampling yourself. It's really not that difficult, and can be very fast, since you reduce each group of 2 pixels to a single pixel. But of course, doing just that, you end up with 3 different grayscale values including black and white, instead of just black and white. So to be able to use fax compression in the destination TIFF, you should apply some flavor of dithering after the resampling.

Joris Van Damme
info@awaresystems.be
http://www.awaresystems.be