2007.07.28 20:23 "Re: [Tiff] Well, How to create a 200x100dpi Tiff file programmatically?", by Toby Thain

On 28-Jul-07, at 5:05 PM, mohamad zeinali wrote:

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> > On 7/28/07, Toby Thain <toby@smartgames.ca> wrote:
> > On 27-Jul-07, at 5:49 PM, mohamad zeinali wrote:
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> > How did you check? Resolution is defined by those three tags. That > comes from working code.

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> I opened the file using Microsoft Document Imaging and it says that > this file has a resolution of 100x100 dpi.

That is almost certainly an issue with the program. It's likely taking one value (not looking at both X and Y), and assuming square pixels. Try a program such as Photoshop CS2 which does support non- square pixels.

You can also try inspecting the TIFF tags with tools provided as part of libtiff, to verify that the resolution is correctly encoded. Do the same thing for known-good files (e.g. fax files) generated elsewhere.

> I've tested any and everything you can imagine! I entered many > different values for XRESOLUTION and YRESOLUTION. According to some

> resources like http://www.asmail.be/msg0055114921.html, the value > we enter as XRESOLUTION is just the offset(from the beginning) of

> real information about resolution. More importantly, inspecting > codes like "bmp2tiff" which is available from:

> http://www.torry.net/vcl/graphics/conversion/bmp2tiff.zip

> shows that we should set the value of XRESOLUTION tag as an offset > in which we write a combination of two 4-byte values.

> Yet, I don't know how to implement this using LibTiff!

You really do need to RTFM (such as the TIFF spec, along with libtiff documentation).

One starting point: http://www.awaresystems.be/imaging/tiff/faq.html#q4

--Toby

> Thanks.
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