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Author Topic: Problem with "Get Image" - Imagesize is reduced to ~25% of actual size  (Read 4620 times)

thrbn

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Hi everyone,

I have to admit that I am quite new to Scribus, but a lot of googling and even more try and error did not help :-)

I am currently making the layout for a photo book with pictures from awesome vacation, the available photo book editors did not satisfy my requirements, so I ended up with the following workflow:
* Darktable to pre-process images, mostly available in Raw. (Input: DNG, Output: TIF)
* The Gimp for finalizing a picture before positioning it in the layout with (Input: TIF, Output: TIF)
* Scribus.

Scribus 1.4.2 is running on my Ubuntu 13.10 64 bit machine.

My Scribus document has a resolution of 6449.00 pt wide x 3260.00 pt in height, printed with 300 dpi this results in a format of 57,85 cm x 28,8 cm.
The image I want to add has a resultion 3225 × 1107 pixels, The Gimp is set to 300 dpi.

The problem is, when I add to an image box with the size of 3225 pt x 1107 pt, Scribus "scales the image to framesize". I didn't even notice the problem until I tried to make my first pdf-print: Scribus warned me that some images did not have 300dpi, but actually 72 dpi.

The thing is, when I set the "Actual x/y-DPI" to 300, it shrinks the image to ~1/4 of the actual size (72/300).

Where do I "lose" the image qualitity? I did not find any settings related to image importing in Scribus or in the manual. Maybe I am looking with the wrong search terms, so it would be great, if you'd help me - I am pretty sure I am just missing something obvious :-)

I found a bug report describing a similar problem, but the bug was flagged fixed and was raised 8 years ago :-(

Thank you very much!

Nermander

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Re: Problem with "Get Image" - Imagesize is reduced to ~25% of actual size
« Reply #1 on: January 04, 2014, 12:29:41 am »
It seems as if you are stuck on the usual misunderstanding.

A digital image DOES NOT HAVE A DPI. Period. No, don't object!

You can set a DPI valu in some digital image formats, however since digital pixels don't have a physical size that is just a "desired print size".

An image of 300x300 pixels printed at 1x1 inches is 300 DPI, even if the numbers in the files says 72 DPI.

An image of 300x300 pixels printed a 2x2 inches is 150 DPI, even if the numbers in file says 72 DPI, 300 DPI, 4711 DPI or 1 DPI.

So, get rid if thinking in DPI. Think in pixels and inches only. Or pixels and mm of you prefer metric.

Get away from the habit of setting the document size in points. Set the document size in inches or mm. Look at how many pixels the images have.

Pixels divided by physical print size is the DPI, there is not other DPI.

thrbn

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Re: Problem with "Get Image" - Imagesize is reduced to ~25% of actual size
« Reply #2 on: January 04, 2014, 12:58:22 am »
Hello - thanks for the reply :-)

I do not object the fact, that an digital image does not have DPI - but in my case I have an image with 3225 px × 1107 px and a page with  6449 px wide x 3260 px.

So, independent from DPI, my image should stretch ~50% wide and ~33% high. It does not, it is 25% of that.
It shows in the image box properties that the image is scaled to more than 400%, which is nonsense, because the image has the exact same size as the image box in pixels.

I have attached some screenshots.

Here you can see the image size:


This screenshot shows the size of the box:


This image shows the automatic scaling of the image in Scribus:


And this image shows what happens when you set the image size to 100%:


I'll try it with settings set to inch/mm, thanks.

Edit: It works when I set the document size in mm in Scribus. But that doesn't make any sense... Especially when everything, the image box, the image and the document is specified in pixel, there should be no offset at all, independent of any DPI setting anywhere...
« Last Edit: January 04, 2014, 01:06:14 am by thrbn »

winxi

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Re: Problem with "Get Image" - Imagesize is reduced to ~25% of actual size
« Reply #3 on: January 04, 2014, 01:15:01 am »
Hi,

I'm also quite new to Scribus. I'm not absolutely sure, but I think that Sribus uses a fixed value of 72 dpi to convert real world measures to pt and vice versa.
Thus, when you set your document to a size of 6449 pt x 3260 pt this actually corresponds to a real world size of 227,5 cm x 115 cm.
The resolution to your problem might be to set the document size to 57,85 cm x 28,8 cm instead of 6449 pt x 3260 pt.

utnik

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Re: Problem with "Get Image" - Imagesize is reduced to ~25% of actual size
« Reply #4 on: January 04, 2014, 01:28:08 am »
hi thrbn

your document has a much bigger size than you expect it…
you're dealing with units you don't understand. as nermander suggested, you should change your document settings to a unit you know (inches or millimeters).
the image box in your screenshot is 3225 pt wide (not 3225 px), this means 113.77 cm or 44.79" – if a picture of 3225 px fills this frame, it has a resolution of one pixel per postscript point (or 72 ppi).

hope, this helps…
utnik

edit: winxi was faster – but it's not the way scribus converts something. it's a confusion with px (real points of the picture) and pt (postscript points – a standardized value, 1/72 of an inch…)
« Last Edit: January 04, 2014, 01:34:39 am by utnik »

winxi

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Re: Problem with "Get Image" - Imagesize is reduced to ~25% of actual size
« Reply #5 on: January 04, 2014, 02:01:10 am »
Thanks utnik for the clarification. I've just looked up the term postscript point - I'm learning something new everyday  :)
As you already stated, the source of the original problem is a confusion of the postscript point pt (which is in fact a real world measure) with the picture element px.

thrbn

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Re: Problem with "Get Image" - Imagesize is reduced to ~25% of actual size
« Reply #6 on: January 04, 2014, 11:06:34 am »
Yip, I thought pt and px are the same  :-X
Thanks for the help!

Nermander

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Re: Problem with "Get Image" - Imagesize is reduced to ~25% of actual size
« Reply #7 on: January 05, 2014, 01:16:25 pm »
And the lesson learned is: Don't assume, find facts! :)

If you think points and pixels are the same, a quick googling of "points pixels" would probably tell if you are right or not.