2006.10.14 13:46 "Re: [Tiff] SamplesPerPixel is 0 when loading image", by Toby Thain

On 14-Oct-06, at 9:29 AM, Anurag Singh wrote:

>

> i have just checked IMG_4224-01.tiff, it has sampleperpixel 3. But > why are you calling this function TIFFGetFieldDefaulted(tif,

> TIFFTAG_SAMPLESPERPIXEL, &samples_per_pixel) to know about > sampleperpixel.

Because that tag may be omitted (default value is 1) - see spec.

--Toby

>
> i always used TIFFGetField( input_tiff, TIFFTAG_SAMPLESPERPIXEL,
> &samplesperpixel );

> and i didn't get any problem with samplesperpixel, outcomes are > always same during my testing period.

>
> Anurag Singh
>
>
>

> On 10/14/06, Marcel Wiesweg <marcel.wiesweg@gmx.de> wrote:

for the application digiKam (www.digikam.org) we are using libtiff in our image loader. A while ago we received a bug report from a user that opening certain 16-bit TIFF images failed. The report was later on confirmed by another user.

Strangely, on other systems (on most systems, including mine) the test image loads without any problems.

We investigated that the problem is that after calling

    TIFFGetFieldDefaulted(tif, TIFFTAG_SAMPLESPERPIXEL, &samples_per_pixel);

the value of samples_per_pixel is "0" on the affected machines, "3" on all others. This has been tested with different versions of libtiff.

The full story can be found here: http://bugs.kde.org/show_bug.cgi?id=125916

The test image is http://amigos.amiga.hu/dudeeg/digikam_tiff/IMG_4224-01.tif

The source of out TIFF loader can be found at

> http://websvn.kde.org/trunk/extragear/graphics/digikam/libs/dimg/ > loaders/tiffloader.cpp?view=auto

Have you any idea what to do about this?