At 22:04 03.03.2002, Michael Ulbrich wrote:
Ah - not off topic
Comment on : Tags in TIFF hold analogous data to the JPEG markers,
Its just the other way round JPEG APP1 sections contains a TIFF header
including IFD0 structure and TIFF6.0 Tags.
As i wrote today morgning (my one) i would prefer adding TIFF support
for GetImageSize and leave it as it is besides that. The new exif module
has some extensions, maybe i split up the information to seperate arrays
to inform where the data comes from...but next version.
marcus
>Marcus Boerger wrote:
> >
> > Hi Rasmus,
> >
> > today i woke up and i think the solution is to have read_exif_data
> > a third parameter whether or not to return information if no exif is
> > present. And to support TIFFs with GetImageSize we only need
> > a small addition of say less than 100 lines c code...
> >
> > marcus
> > --------------------------------------
> >
> > [sorry first one has gone to wrong mailing list - so here again]
> >
> > Hi Rasmus,
> >
> > i think Serge is correct because one can use standard functions for
> > FileName,FileDateTime and FileSize. So better reply with false.
> > The other solution would be adding an array entry 'EXIFPresent'
> (true|false)
> > BUT i think that is not so good.
> >
> > From my point of view i would like to discuss the difference between
> > getimagesize and read_exif_data a little:
> >
> > We would need some function*ality* from exif.c in image.c to support TIFF.
> > When we have those functions we would be able to interpret APP markers
> > of JPEG also (see below).
> >
> > I suppose we check whether or not ext/exif is present and then return
> > read_exif_data results in GetImageSize (i do not see the point of returning
> > and APP marker section which has to be interpreted). Then we should also
> > make ext/exif default to present and change switch from --enable-exif to
> > --disable-exif (prefer this).
> >
> > Or we move the necessary functions from exif.c to image.c and
> > then make ext/exif optional for editing exif headers in the future.
> >
> > If to many people use APP return info we could use a third parameter to
> > return interpreted values.
> >
> > The real point here is that i do not know what APP markers and EXIF
> > headers have to do with GetImageSize but we have the information when
> > adding TIFF support.
> >
> > what do you think?
> >
> > marcus
> >
> >
>
>-----------------------------------------------------------------------------------------------------------
> >
> > #6787
> > [17 Sep 2000 6:07am] [EMAIL PROTECTED]
> > Hi Guys,
> >
> > It seems that read_exif_data builds certain fields like
> > FileName, FileDateTime, FileSize etc .. even when no real
> > EXIF data exists. So read_exif_data will always return something....!
> >
> > This makes it a pain to test for the presence of actual EXIF data cause
> > I have to do something like this:
> >
> > $exif_data = @read_exif_data($upload);
> > if (isset ($exif_data['CameraMake'])) {
> >
> > Not very bullet proof ....
> >
> > Would be nice if it would not return anything without the presence of
> > actual EXIF data.
> >
> > Thanks, Serge
> >
> > #14994
> > [11 Jan 6:07am] [EMAIL PROTECTED]
> > I know, that Rasmus made the implementation for this function and that
> > he used the header readouts from an imageinfo.c, but I'm missing the
> > ability to identify TIFF images.
> > As i'm not firm with imageheaders, I'd like to ask someone to implement
> > this feature.
> >
> > --
> > PHP Development Mailing List <http://www.php.net/>
> > To unsubscribe, visit: http://www.php.net/unsub.php
>
>Hi Marcus, Rasmus,
>
>I'm rather new to this list, just lurking for some time now. Please
>excuse me, if this is slightly off topic.
>
>I've come across some weird results from GetImageSize() in $info[]
>myself and have sent a comment w/ patch to bugs #15174 and #13213 of
>which the latter is not that important IMO.
>
>On the topic of EXIF headers:
>
>The ext/exif/exif.c code does basically the same as in standard/image.c:
>it parses the JPEG header structure and extracts the different markers.
>In image.c we have a function iptcparse(), which further interprets the
>APP13 markers content. In ext/exif/exif.c there is read_exif_data().
>Since the EXIF header is identical to the APP1 marker (M_EXIF == M_APP1
>== 0xe1), why not have a function exifparse() in standard/image.c which
>will interpret the APP1 (aka EXIF header) marker's content and get rid
>of ext/exif?
>
>AFAIK there's a third data structure in the JPEG headers which might
>become interesting to image processing apps in the future: the APP2
>marker contains ICC profiles, which are needed for color management ...
>
>Adding TIFF support:
>
>A corresponding situation exists when adding TIFF support. Tags in TIFF
>hold analogous data to the JPEG markers, especially the above mentionend
>substructures will be present. So wouldn't it be great to call
>GetImageSize() on a TIFF and return $info[], which has elements
>$info["IPTC"], $info["EXIF"] and info["ICC] reliably set?
>
>HTH ... Michael
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