How to get a PDF to print at 600 DPI

[Muzician]

The place I want to have print my image says they prefer pdf, the maximum dpi they can print at is 600 dpi. However, pdf doesn't save at anything but 100 dpi even if I convert a 600 dpi .jpg or .xcf file. 

If I want the maximum 600 dpi quality at the particular dimensions I want with a pdf file, what's the process when going from a jpg or xcf file?

Thanks!

[rich2005]

Gimp will open a PDF with a resolution of 100 ppi regardless of what the original is. Up to the user to set the value. A screenshot of what to look for here https://www.gimp-forum.net/Thread-Import...5#pid32225

If your Gimp image is created with height x width @ large-ppi and exported as a PDF then the encapsulated image will be @ large-ppi

Gimp does not make very compact PDF's The internal compression is low and you might fall-foul of file size restrictions. In that case export your image as a jpg and use some other application to make the PDF - suggestions LibreOffice / Scribus / ImageMagick

[rich2005]

First read the previous post.
Looking at your other posts to get the context, you are running into PDF issues. 600 ppi is a suitable value for printing an image of a postage  stamp but not for a poster. Probably 200 ppi is more suitable.

However, I used 300 ppi in the video demo, I would not go above that.

The procedure is 
Make a new empty canvas at the required size and ppi
Drop your image into it (or copy/paste if you want)
Scale that to fit
Export as a PDF

...and that gets you a large PDF

For a smaller PDF file size use ImageMagick http://www.imagemagick.org  and a command

Code:

magick infile.jpg outfile.pdf

about 5 minutes  https://youtu.be/TysvSEfd-is  there might be something in there that helps.

[Muzician]

(12-21-2022, 01:06 PM)rich2005 Wrote: First read the previous post.
Looking at your other posts to get the context, you are running into PDF issues. 600 ppi is a suitable value for printing an image of a postage  stamp but not for a poster. Probably 200 ppi is more suitable.

However, I used 300 ppi in the video demo, I would not go above that.

The procedure is 
Make a new empty canvas at the required size and ppi
Drop your image into it (or copy/paste if you want)
Scale that to fit
Export as a PDF

...and that gets you a large PDF

For a smaller PDF file size use ImageMagick http://www.imagemagick.org  and a command

Code:

magick infile.jpg outfile.pdf

about 5 minutes  https://youtu.be/TysvSEfd-is  there might be something in there that helps.

I really appreciate the effort you went to - making and uploading a video. 

Is there any downside to using 600 dpi? This is a reproduction of a painting a relative did so I'm looking to squeeze every bit of resolution possible under the circumstances. I'm conscious that I'm going to lose a certain amount of resolution just due to the limitations of the printer.

Also, if I export from the xcf file to jpg first as an intermediate step it means I'm making the pdf off the slightly less sharp jpg which defeats the purpose of retaining as much quality as possible. When I compare the 600 dpi jpg vs the forced 600 dpi pdf  both made from the 600 dpi xcf file I do see a small difference in the fine details - it's not profound but it's discernible. At that point it seems I might as well have them print the jpg file, or is there still an advantage to using pdf?

[rich2005]

Quote:At that point it seems I might as well have them print the jpg file, or is there still an advantage to using pdf?

I agree, no advantage in your case, for using a PDF. Remember the D(ocument) in PDF. It is a format best suited to text or mixed text and some graphics. Text in the PDF is a vector format and when the font metrics are included in the PDF the document is viewed or printed correctly. Which is why printers like them.

When it comes to Gimp (or ImageMagick) your bitmap image file is just "wrapped" in a PDF and quality depends on the image. Viewing a PDF, depending on zoom value, will result in on-the-fly scaling and your image will look different to the original.

Your quality problem is you are coming from a low base. 72 ppi which when Print Size is adjusted (42" -> 24") ends up as about 120 ppi. No scaling is used for that, quality is what you originally have, anything else requires scaling, interpolation and degradation.

For regular viewing at a distance 120 might be ok see: http://resources.printhandbook.com/pages...inting.php

If you want it for close inspection and 300 ppi then you are scaling the image 2.5 times and you might get away with that, 600 ppi = x5 and expect fuzziness.

Then it depends on the printing company. This from the one I use.
All prints larger than 18″x 12″ are printed on our Chromira printer and these should be supplied at the required print size at 300 ppi. (For good quality we advise at least 200ppi.) and follows up with, use a jpeg with 95-98 quality or an uncompressed tiff.

That is a photographic laser printer which has a high dots-per-inch (dpi, not the same as image ppi)

Best guess the printing company gives not so specific advice.

If you use the procedure outlined in the video, anything you plant on the blank canvas uses the canvas ppi, 200 / 300 ... as you set up. Export as a (95) jpeg and hope the file size is not too large for acceptance.


Edit I see from your other posts "I'm using a 4k TV as my monitor"
Strictly, for accurate results your Monitor should be color-calibrated using a calibration device. No one expects you to do this for a one-off but you should be aware of:

What you see is almost certainly brighter than when printed. I am not sure this will work with a tv but there is a simple brightness adjuster here: https://www.cambridgeincolour.com/tutori...ration.htm

If printed using an inkjet printer, then because of the cyan-magenta-yellow inks some brighter colours become muted (bright green for example)