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Author Topic: Setting resolution of pdf export  (Read 638 times)

freya_h

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Setting resolution of pdf export
« on: May 29, 2017, 04:46:14 pm »
Hello everyone,
I'm fairly new to Scribus and haven't been able to find a solution to this issue in the forum...

1. I want to export a file as pdf (1.4) in at least 300 dpi resolution for printing. I have tried different settings for "maximum image resolution" and "resolution for EPS graphics", but in the end, the file is always exported at 72 dpi. How do I change this?

2. Since the printer also accepts jpg and tif files, I tried exporting the file as an image. However, jpg and tif are not shown as options in the dropdown, only bmp, png, ppm, xbm and xpm. Why do I not have all options available? I'm using Scribus 1.4.6 on Mac.

Thanks

a.l.e

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Re: Setting resolution of pdf export
« Reply #1 on: May 29, 2017, 07:04:24 pm »
hi freya

welcome to scribus!

a quick answer:

- you should export (and deliver to the printer) a pdf. ignore the other formats.
- if possible, you should not change the resolution when exporting. you should crop and scale your image in an image editor so that they match the final resolution.
- if possible, you should not use eps images, but -- depending on the content of the image and the source --:
  - jpg (for normal photo and a "normal" output)
  - tiff (for a photo and high quality/resolution output)
  - png (for logos or images that are not a photo)
  - svg (or pdf) if the eps is a vector image.

does this somehow answer your question?

ciao
a.l.e

freya_h

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Re: Setting resolution of pdf export
« Reply #2 on: May 29, 2017, 11:27:06 pm »
Hi a.l.e.,

If I understand correctly, you are suggesting that I export the file to pdf at 72 dpi and then scale it to 300 dpi using an image editor. However, that seems unnecessarily complicated since I had already set up the file in Scribus to be exactly the desired print dimensions. is there no way to simply change the export resolution?

thanks!

a.l.e

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Re: Setting resolution of pdf export
« Reply #3 on: May 30, 2017, 10:52:28 am »
no, i'm suggesting you not to use EPS files.

use TIFF, JPEG or PNG (or SVG) instead. depending on the content.
and prepare those file outside of scribus to match the final size you need in your pdf.

afaik, scribus will not embed your EPS file as is in the PDF file and uses an external tool to
that's why you're asked to define an export resolution.
but scribus can embed TIFF, JPEG and PNG as is in the PDF (and convert SVG to native shapes).

EPS is a format "of the past"... and in most cases you there are formats that better fit the task...

GarryP

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Re: Setting resolution of pdf export
« Reply #4 on: May 30, 2017, 11:50:31 am »
freya_h, I think you might need to give more information about what is happening.

A PDF file does not have a resolution in and of itself. To say that another way, a PDF is "resolution independent". This is why you can zoom in almost infinitely without losing definition in the vectors (including text).

However, when you include raster images (bitmaps) in a document, each of those images has its own resolution which is based on both the number of pixels in the image and the size it is displayed at. For example, an image that is 600x300 pixels inserted into a 2" x 1" frame will have a visible resolution - when exported - of 300 PPI (pixels per inch). 600 pixels divided by 2 inches equals 300 pixels per inch. The same image when inserted into a 4" x 2" frame will have a PPI of 150 (600 pixels divided by 4 inches equals 150 pixels per inch).

NOTE: DPI - dots per inch - and PPI are, for the most part, interchangeable concepts. Scribus mixes the two which can be a little confusing. DPI is only really relevant at the time of printing but these days you can pretty much think of them as being the same thing. (If any purists have a problem with this then this really isn't the time or place to argue about it.)

Therefore, if you insert a 600x300 pixel image into both a 2" x 1" and a 4" x 2" frame in the same document then the 2" x 1" image will be at 300 PPI and the 4" x 2" image will be at 150 PPI. There's nothing you can do about this. There are only so many pixels to go around and they have to fit in the space you put them in.

NOTE: If you look at the properties of an image file in GIMP (or whatever) you may see that an image has been given a resolution, usually 72 DPI. This resolution is mostly irrelevant and can be taken as nothing more than "a serving suggestion". You can ignore the resolution given in the image itself as the only resolution you should be interested in is the resolution the image has when it is exported which, as I've said above, is purely dependant on the number of pixels and the image frame size.

To wrap up what I've said so far: When talking about images, a PDF is simply a container for those images and each image has its own resolution. Because of this, a PDF cannot be "exported at 72 dpi". A PDF file has no resolution but each image within it has its own resolution.

However, when you export a document from Scribus you can set a maximum resolution for images. If you do not set the maximum resolution for images then Scribus will export all images at the resolution which is inherent to the number-of-pixels/frame-size relationship I've explained above. On the other hand, if you DO set the maximum resolution then Scribus will make sure that no image - when exported - will exceed this maximum.

For example, say you have three images in your document: (a) 600x300 pixels in a 2" x 1" frame - 300 PPI, (b) 600x300 pixels in a 4" x 2" frame - 150 PPI, and (c) 600x300 pixels in a 8" x 4" frame - 75 PPI. If you set the maximum resolution to be 150 PPI, the images will be exported at (a) 150 PPI, (b) 150 PPI, and (c) 75 PPI. No image will have an exported resolution above the maximum resolution that was set.

However, images that have resolutions lower than the maximum resolution will not be given a higher resolution to match the maximum resolution as this is impossible. The image only contains as many pixels as it contains. If you have 75 pixels that are displayed within a 1" space then the number of pixels per inch will be 75. Scribus cannot conjure more pixels out of thin air to take the PPI up to 150 (or whatever else). It can only use what it has.

This all means that any exported document will - unless you have been very careful with your choice of images and layout - have images that are a mixture of resolutions (with a maximum resolution of whatever has been set, if it has been set).

Does any of the above explain what is happening to your document? Or is something else happening?

As for your second question, I have no idea why the Mac version of Scribus cannot export as JPG or TIF. Scribus is built using something called Qt, and also uses various code libraries to help it perform various functions. I can only assume that either Qt or one of these code libraries is stopping Scribus from exporting to certain formats on OS X. (Or the developers have missed something.)

Various bug tracker tickets for this were raised years ago:
* https://bugs.scribus.net/view.php?id=12993
* https://bugs.scribus.net/view.php?id=10334
* https://bugs.scribus.net/view.php?id=11739
...but I have no idea whether it's been fixed or not, it's difficult to tell from the comments. Maybe in 1.5.x?

In addition to all of this, don't concern yourself with exporting to image files (JPG, PNG, etc.) at the moment. You're trying to export to PDF so that's what you need to look at. The exporting to image thing is just clouding the issue and bringing in other things - like EPS - that aren't relevant. Let's stick to getting your PDFs exported nicely and then we can look at image exports if that's something you really need to look at.

 

palmate