Question to "Origin"

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herb
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Joined: Sat Jul 18, 2009 3:19 pm

Question to "Origin"

Post by herb »

Hello Pierre,

XnViewMP version 1.00 has a tag "Origin" in: Info area --> tab properties --> images
My first thought was it is "Orientation" or similar, because for all my images "Top Left" is displayed.

Today I did a test with images that have different values for "Orientation".
BUT XnViewMP always shows "Top Left".

So my question is: what value is really displayed?

Thanks for your help in advance.
Best regards
herb
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xnview
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Re: Question to "Origin"

Post by xnview »

it's not always the orientation, but how the image is saved.
Pierre.
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XnTriq
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Re: Question to "Origin"

Post by XnTriq »

herb
Posts: 218
Joined: Sat Jul 18, 2009 3:19 pm

Re: Question to "Origin"

Post by herb »

Hello Pierre, hello XnTriq,

thanks for your replies.

@Pierre:
it's not always the orientation, but how the image is saved.
Sorry, but I miss a scenario where this tag/value changes. Can you please give a detailed one.
My 2nd question is where is this value stored / taken from for display.

@XnTriq:
Sorry, I cannot answer your question. There are so many scenarions with orientation and I do not have the overview how XnViewMP should behave.

Best regards
herb
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xnview
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Re: Question to "Origin"

Post by xnview »

for example:

TIFF: it's the field orientation
BMP and other formats: often images are encoded bottom to top
Pierre.
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XnTriq
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Re: Question to "Origin"

Post by XnTriq »

xnview wrote: Mon May 09, 2022 12:31 pmfor example:

TIFF: it's the field orientation
BMP and other formats: often images are encoded bottom to top
… like Truevision Targa:
ToolsSettings…FormatsWriteTGABottom-up orientation
https://en.wikipedia.org/wiki/Truevision_TGA#Header wrote:Bit 4 of the image descriptor byte indicates right-to-left pixel ordering if set. Bit 5 indicates an ordering of top-to-bottom. Otherwise, pixels are stored in bottom-to-top, left-to-right order.

Thanks for clarifying, Pierre!
herb
Posts: 218
Joined: Sat Jul 18, 2009 3:19 pm

Re: Question to "Origin"

Post by herb »

Hello,

thanks for your quick replies.
But I am still confused:
Tag Exif:Orientation is used for the current orientation of the image.
As far as I know also in case of *.tiff or also *.bmp images.
Or do I miss somethings?

How can it be used for something like "but how the image is saved" (as Pierre wrote).
Thanks in advance for giving me more details.

I also did some experiments storing *.tiff images. But origin alsways was: Top left
Can you tell me the steps in order to get another value for "origin"

Best regards
herb
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XnTriq
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Re: Question to "Origin"

Post by XnTriq »

Does this answer (part of) your question, herb?
Pixel grid origin = top/left:

Code: Select all

0  a  b  c  d
1 1a 1b 1c 1d
2 2a 2b 2c 2d
3 3a 3b 3c 3d
4 4a 4b 4c 4d
Pixel grid origin = bottom/left:

Code: Select all

4 4a 4b 4c 4d
3 3a 3b 3c 3d
2 2a 2b 2c 2d
1 1a 1b 1c 1d
0  a  b  c  d
herb
Posts: 218
Joined: Sat Jul 18, 2009 3:19 pm

Re: Question to "Origin"

Post by herb »

Hello XnTriq,

thanks for all the links. A very good private lession for me (although I have not read everything till now).
Things become clearer and clearer.

Best regards
herb