2006.10.14 21:22 "Re: [Tiff] SamplesPerPixel is 0 when loading image", by Toby Thain

On 14-Oct-06, at 10:53 AM, Anurag Singh wrote:

>
> On 10/14/06, Toby Thain <toby@smartgames.ca > wrote:

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.

> yeah. i have seen spec, but we are using libtiif here, so we have
> to see this function only
> int TIFFDefaultDirectory(TIFF* tif), Act the point is this libtiff

> take care of it, if tag is not present then it always return > default value for important tags such as for samplesperpixel.

I don't happen to use that function.

--T

>

> If you don't believe then you can check it.

Anurag Singh

--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 we are using ( www.digikam.org)

>> 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?