[Libreoffice-bugs] [Bug 132658] ENHANCEMENT: Image without resolution set should get a default fallback resolution (not based on a screen resolution)

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=132658

Telesto <telesto at surfxs.nl> changed:

           What    |Removed                     |Added
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                 CC|                            |rb.henschel at t-online.de

--- Comment #17 from Telesto <telesto at surfxs.nl> ---
(In reply to Dirk Munk from comment #16)

> Let me start with a general remark. If you want to insert an image in a text
> document, then it is very wise to prepare that image in image editing
> software (Photoshop etc.), to give it the dimensions and resolution (in dpi)
> that you want. That way, you can insert the image as-is, and you don’t have
> to use Writer to modify its properties. 

Yes/ no, not everybody works this way. Have seen enough images without DPI from
various users.. 

> 
> Back to the problem. An image has a size in pixels, but not in cm or inch.
> The dpi setting in the Exif header will tell software like writer how big
> the image should be in the document. This dpi setting is just a kind of
> comment, comparable to your name in the header as copy right holder. If you
> change the dpi setting, the size of the image on the page will change
> obviously, but (and this is important) nothing is done (or should be done)
> to the image itself.
> 
> Often the dpi setting in the Exif header is 72 or 96 dpi, camera’s will add
> that setting. It is a rather silly setting. Now, what should happen if you
> insert a picture that would be to big for the page, let’s say that with the
> dpi setting in the header, it would be 20 inch of 50 cm wide on a page with
> 17 cm between the left and right margin. Should Writer keep the dpi setting,
> and reduce the number of pixels in the image to get the image fitting
> between the margins? NO, NO, NO !! Writer should change the dpi setting, and
> leave the image itself untouched. 

LibreOffice does nothing to the image file itself.. Only after compress..
So no data is lost at all

My issue is about dimensions of the image on insertion. If an image file is
lacking a embedded DPI setting the "Original size" is calculated on screen
DPI.. On insertion it shrinks between the page margins (increasing the DPI).

The original size of in image being actually intended as 300 DPI (without being
embedded) will result in large "Original size"

The cat shape is imported within page margins on my 96 DPI system ( so actual
size on screen 16,93 cm x 12,70 cm)
The same file imported from a mac with 135 DPI screen results on an image in
document size at insertion of 11,95 cm x 8,96 cm). 

So the 'actual dimensions" are based on screen resolution.. While the apparent
dimensions are based the 'actual size' of the image in the document. [How
confusing can actual actually be terminology wise]

> 
> Further manipulations with the size (in inch or cm) of the image on the
> page, should also just change the dpi setting. When you’re finished with
> these manipulations, then you should have a look at the resulting dpi
> setting. Let’s say it is 1000, that is a rather silly dpi setting for a
> printable page. Then you can reduce it to 300 dpi (for instance), and Writer
> will recalculate the number of pixels and actually change the number of
> pixels.
> 
> What if an image has no dpi setting in the header? Simple, let Writer fit it
> between the margins, and let it calculate a dpi setting. Remember, the dpi
> setting is just comment in the Exif header. Then adjust the size of the
> picture, and when you’re done give it the dpi setting you require and let
> Writer recalculate the pixels. 
> 
> In other words, I don’t think adding ‘just’ a dpi setting of for instance
> 200 dpi is the best solution for your problem.

It's about the DPI for calculating the size of an image on insertion when the
file is lacking a embedded DPI. There is no actual manipulation of the image..
Shrink the image afterwards, will decrease the dimensions and increase the DPI.
Enlarging the image will increase the dimensions and decrease the DPI from 200
to...

This would also "solve" the cropping issue of images on screens with different
resolutions. However, this wouldn't fix older documents (or probably make it
even worse; so probably something more nifty thing is needed)

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