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

[Bruce Steers]

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 ]----
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.gambas-basic.org/pipermail/user/attachments/20221206/f077d8d1/attachment.htm>