Exporting with exact size in pxls

Software darktable
1

Hi all,
I am exporting for printing with exactly defined size in pixels, for instance 2480x3602 (after setting up right proportions of the photo in the crop&rotate module). However, the output file has slightly different size/proportions - 2480x3600. Why is that? I have allowed upscaling and resampling (even if not needed in this case). Tell me please if I missed something.
Thanks in advance for your feedback.

2

this can be the same rounding issue I have reported earlier https://github.com/darktable-org/darktable/issues/9738.

3

Or even simpler: dt tries to stick as close as possible to the aspect ratio of the full-sized image, and considers the dimensions you give as maximum values for the exported image(s).

So you could try adding a few pixels to the shortest size (or removing a few from the longest),

4

That seems indeed to be the issue of initial proportions. However, it is very hard to find the exact ones. When playing with parameters I end up with different values, like 2377x3602 or 2480x3599. I would like dt to resample/upscale to the right values as these are the expected values by my printing service.

5

Perhaps the easiest way to get exact proportions is to define the crop and the export size in such a way that you know which dimension will be exact, and ensure that the other dimension is some pixels too large. Then use a program like the GIMP or Imagemagick to crop to exact dimensions (with no scaling whatsoever needed).

Trying to do it only in dt is probably going to be a very frustrating exercise, between the cropping and the rounding needed on export.

6

Thanks. I was hoping to rely purely on dt :-(.

7

My workflow would need to be:

  • develop a photo in dt, export it in TIF with a certain reduced size, close to desired proportions
  • load the TIF in GIMP and fine tune the crop
  • load the finally cropped image back in dt and sharpen it for a print and export as JPG

I will have to give it a try.

8

Why not sharpen in the GIMP at the final size? It is a capable program.
Though I wouldn’t use it for most of my editing (dt being more flexible and designed for photography) small corrections like sharpening are easy enough to apply, and it avoids another switch.

9

You can do points 2 and 3 using imagemagick from the command line, and script it to do it in all images at once

1 Like