Author Topic: Importing images - low resolution?  (Read 225 times)

artdude

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Importing images - low resolution?
« on: August 31, 2019, 01:50:36 am »
When I import an image, the selection window shows that my image is 72 x 72 dpi - but I know that the image is really 300 dpi. Is the 72 thing just showing how it will be displayed for Scribus, or is Scribus actually lowering the resolution of my image? I exported a PDF and it looks higher/proper resolution there, but I just want to make sure of why it's saying "72 x 72". Thank you.

utnik

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Re: Importing images - low resolution?
« Reply #1 on: August 31, 2019, 11:39:26 am »
hi artdude

the resolution of your image is 1596×1509px – that's what really counts!

the exif data of some image files contains an intended output resolution. in this case scribus will show this resolution, and depending on your settings it might scale the image to this resolution. (i prefer to have the images scaled to frame size first…)
whens scribus shows 72×72, there's either no defined resolution or it is really set to 72×72 ppi.

but what your output will be depends on the image size in your layout. with 300 ppi your image will be around 135×128 mm (or if you scale the image to fill an a4 page the resolution will be 136 ppi…)

utnik

a.l.e

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Re: Importing images - low resolution?
« Reply #2 on: August 31, 2019, 12:18:25 pm »
this question seems to be rather popular...

i'm writing a more detailed answer and i would be glad if people would contribute and improve it so that we can publish it and link it!

more to come...

RodneyLee

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Re: Importing images - low resolution?
« Reply #3 on: August 31, 2019, 03:39:51 pm »
if I recall all .JPG files are shown at 72 dpi so like utnik say it's the Pixels that count, a 5 x 5 image at 300 dpi is 1500 x 1500 pixels, make that image any smaller or larger and the dpi changes

utnik

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Re: Importing images - low resolution?
« Reply #4 on: August 31, 2019, 09:59:06 pm »
hi rodney

if I recall all .JPG files are shown at 72 dpi…
no, not all of them. i have a whole lot of .jpg images with a defined output size of 314 ppi as a part of the exif data. but lots of image processors don't write an output resolution into the files and others write 72 unless the user changes the value.
as scribus shows 72 when the value is missing, most .jpg files will show like that – but not all…

utnik

Nermander

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Re: Importing images - low resolution?
« Reply #5 on: August 31, 2019, 10:48:31 pm »
this question seems to be rather popular...

i'm writing a more detailed answer and i would be glad if people would contribute and improve it so that we can publish it and link it!

more to come...

I have written a post before somewhere in the forum, explaining how an image that is 1200x1200 pixels becomes different DPI depending on how big it is printed.

artdude

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Re: Importing images - low resolution?
« Reply #6 on: September 01, 2019, 04:17:01 am »
From what I can see in exporting PDF's, the "72x72" seems to just be for Scribus, as the PDF, when zoomed in, still looks crisp/high resolution. The ultimate test would be to try and print it out, which I haven't done yet.

Thanks for all the replies.

a.l.e

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Re: Importing images - low resolution?
« Reply #7 on: September 01, 2019, 11:09:02 am »
hi nermander,

i'm going through your posts about resolutions... i already found a link where there are a few interesting inputs...

and i've submitted a request to remove the information about the image resolution from the "import image" dialog:

https://bugs.scribus.net/view.php?id=15796

Nermander

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Re: Importing images - low resolution?
« Reply #8 on: September 01, 2019, 02:31:31 pm »
Maybe an alternative to removing the information would be to label it differently (but I am not sure how to label it to avoid misunderstanding...).

The point is that for people who understand the value it may sometimes be useful (to avoid importing the wrong image).

RodneyLee

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Re: Importing images - low resolution?
« Reply #9 on: September 01, 2019, 04:44:25 pm »
thought I'd through in an example of how PPI changes with the image size

a.l.e

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Re: Importing images - low resolution?
« Reply #10 on: September 02, 2019, 09:29:53 am »
nermander, what's the context when somebody  would profit from looking at the resolution?

personally, i only look at the name and the preview... and if i really have used bad names i check the size in pixels.
i mean, it's not that you have two images, one with 299 and with 300 dpi... and the differences in sizes are so big that you can tell at first sight if it's the right image or not.

i have to admit that the information does not disturb me at all. it's very easy to ignore.
but it's also of so little value, that i 100% for removing it, if other people are confused by it.
(in other contexts, like the "images manager" i'm fine with the image resolution being shown. but in the "file > import" dialog, the value loses all of its value as soon as you click on the ok button)
« Last Edit: September 02, 2019, 04:24:09 pm by a.l.e »

Nermander

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Re: Importing images - low resolution?
« Reply #11 on: September 02, 2019, 07:28:35 pm »
For example if someone has the same image saved in different resolutions. It might not be obvious which version is the one intended for 150 DPI if you only look at the number of pixels.

Say you have two versions of the image, do you know if they are intended for 150 and 300 respectively or if they are intended for 300 and 600? Both situations would have the same ratio of pixels.

But of course that requires the images to have been saved with a correct DPI information.
« Last Edit: September 02, 2019, 07:31:01 pm by Nermander »

utnik

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Re: Importing images - low resolution?
« Reply #12 on: September 02, 2019, 09:04:59 pm »
Say you have two versions of the image, do you know if they are intended for 150 and 300 respectively or if they are intended for 300 and 600? Both situations would have the same ratio of pixels.

well, if they still have the same length and width in pixels, it usually doesn't matter wich one you chose.
a difference will only appear if your settings tell scribus to place the images at a scale factor of 100%.

utnik

Nermander

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Re: Importing images - low resolution?
« Reply #13 on: September 02, 2019, 10:45:52 pm »
I am saying if you have one image that is 500x500 pixels and the other one is 250x250 pixels, they can be intended for 150 DPI and 300 DPI or 300 DPI and 600 DPI.

Say you have dozens of images, each of them is provided in 2 or 3 different resolutions. Some are for 150 and 300, some are for 300 and 600 and some are for 150, 300 and 600. It would make things a lot easier to find the right image if the import dialog showed the DPI.

But to make it more clear to users I think Scribus should differiate between "Specified DPI" and "Calculated DPI" (but maybe better names).

a.l.e

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Re: Importing images - low resolution?
« Reply #14 on: September 02, 2019, 11:13:35 pm »
thanks for sharing the workflow!

i'm still not really convinced and i think that you have better ways to make sure that you can pick the right image...

since you cannot have images with the same name on a disk, and since dpi are important to you, i guess that you will be naming your images:

- landscape-300.jpg
- landscape-600.jpg

otherwise, how can you know that you've set the different DPIs in the images?

and if you're organizing your images in such a systematic way, you're probably using some sort of image manager, which is showing your the resolution you have defined... and it will be much better (filtering!) for you to drag and drop your images from there into scribus and avoid using the scribus own load dialog.

you're in a rather specialized workflow where you already know the size of the frame where the image will be placed... you should have better means for checking the size of the image than looking at the resolution in the file > import > image dialog...

 

palmate