[Gambas-user] Is exif Orientation obtainable without any exif libs/commands?

[Tim Dickson]

why don't you look at the exif lib (that may not be on a system), and 
see how it does it. that should give you a pointer on implementing a 
gambas-only version.
this doc may help.
https://www.media.mit.edu/pia/Research/deepview/exif.html

looks like you need the 0x0112 tag.

regards, Tim

On 05/12/2022 17:17, Bruce Steers wrote:
>
>
> On Mon, 5 Dec 2022 at 16:20, Rolf-Werner Eilert <rwe-sse at osnanet.de> 
> wrote:
>
>     Am 05.12.22 um 17:06 schrieb Bruce Steers:
>     > So i've found exiftool is a tool to easily retrieve Orientation
>     flag
>     > from an image but it's not on all systems, not by default at least.
>     >
>     > Was wondering if anyone has a method to retrieve exif flags from an
>     > image or the Orientation one at least?
>     >
>     > I found rotating and saving an image back to file removed it's
>     > Orientation flag so that's cool.
>     >
>     > But I also found that to save a similar size file back i needed an
>     > instruction like...
>     > hPicture.Save(sPath, 92)
>     >
>     > I had to play with the quality value and found 92 about the
>     right value
>     > for a similar size file.
>     > Wondered if there was a better way to save the image back with
>     identical
>     > file size (i assume a rotated image to be the same mass/size)
>     >
>     > Ultimately I'm looking to spin my images round to be correct way
>     up with
>     > zero quality change.
>     >
>     > The only piece of the puzzle gambas seems to lack is detecting
>     the exif
>     > Orientation flag.
>     > Something in my mind suspects gambas Read could possibly be able
>     to get
>     > the data from the files?
>     >
>     > Respects
>     > BruceS
>     >
>     >
>     >
>     > ----[ http://gambaswiki.org/wiki/doc/netiquette ]----
>
>     Without looking in detail, but it should be in different positions
>     depending on the file format. So for instance you would have to know
>     where and how it is saved in a jpg file, open the file in binary
>     mode,
>     and jump to the information. The same with other file formats.
>
>     Or did I get you wrong?
>
>     Regards
>     Rolf
>
>
> Yes that's what I'm "suspecting" may be possible.
> Just wondering if anyone has tried and failed, or tried and succeeded ?
>
> looks like it's possible. I found this page...
> https://gist.github.com/yepitschunked/9d2e73d9228f5a0b300d75babe2c3796
> Has something i may be able to convert.
> And plenty to study
> https://www.media.mit.edu/pia/Research/deepview/exif.html
>
> Just hoping someone else might have already looked into it and have 
> some working or unfinished code or just information they might share 
> on the topic before i have to start at square 1.
>
> Respects
> BruceS
>
>
> ----[http://gambaswiki.org/wiki/doc/netiquette  ]----
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