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

[Fabien Bodard]

Hi Bruce,
Have you try my thumbnail class ?

It can return a well orientated thumbnail.

And thumbnails are stored like all file browser following the freedesktop
thumbnails spécifications.



Le mar. 6 déc. 2022 à 16:00, Bruce Steers <bsteers4 at gmail.com> a écrit :

> Cheers Tim, yeah i'm investigating. (already found that page:) )
>
> Might look into a gb.image.exif component or something here as exif has
> quite a lot more than Orientation info, like ready made thumbnails for one.
>
> Could be worth looking into.
>
> Respects
> BruceS
>
>
> On Tue, 6 Dec 2022 at 14:31, Tim Dickson via User <
> user at lists.gambas-basic.org> wrote:
>
>> 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 ]----
>>
>>
>>
>> ----[ http://gambaswiki.org/wiki/doc/netiquette ]----
>>
>
> ----[ http://gambaswiki.org/wiki/doc/netiquette ]----
>
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