Clipping minimum dimensions 1200x800px

Siegfried · June 9, 2025, 3:30pm

I can’t use the cropping tool to crop images measuring 1200x800px (not 3:2) for use as WordPress images. Yes, I can set the resolution when exporting, but how do I crop them? 1978x1319 is the smallest (see image).

The background is a scan of a 70MP aerial photograph.

Thank you for your help.

Best regards,
Siegfried

paperdigits · June 9, 2025, 3:42pm

Why not? This is how you would do it.

raublekick · June 9, 2025, 4:00pm

It seems like the crop tool has a minimum crop size that is relative to the size of the RAW. I just tried an image from a a 24MP RAW file and a 16MP RAW file and each had a different minimum crop size.

On the images from my 24MP camera it’s quite obvious based on the numbers: The original image is 6000 x 4000 and the minimum crop using the same aspect ratio is 600x400. That’s a clean 10% on each dimension.

Out of curiosity I looked through the code on github and I think this is where it’s enforcing that:

github.com/darktable-org/darktable

src/iop/crop.c

master


      
          }
          if(g->cropping & GRAB_TOP || g->cropping & GRAB_BOTTOM)
          {
            float yy = (g->cropping & GRAB_TOP) ? (pzy - bzy) : (bzy - pzy);
            ratio = fmaxf(ratio,
                          (g->prev_clip_h - 2.0f * yy) / g->prev_clip_h);
          }
          
          // ensure we don't get too small crop size
          if(g->prev_clip_w * ratio < 0.1f)
            ratio = 0.1f / g->prev_clip_w;
          if(g->prev_clip_h * ratio < 0.1f)
            ratio = 0.1f / g->prev_clip_h;
          
          // ensure we don't have too big crop size
          if(g->prev_clip_w * ratio > g->clip_max_w)
            ratio = g->clip_max_w / g->prev_clip_w;
          if(g->prev_clip_h * ratio > g->clip_max_h)
            ratio = g->clip_max_h / g->prev_clip_h;
          
          // now that we are sure that the crop size is correct, we have to adjust top & left

I don’t know if there’s a technical reason for this or not. Having some minimum is good so that users can’t essentially make the clipping area disappear (even though it can easily be reset it could be confusing).

rvietor · June 9, 2025, 4:04pm

There is indeed a minimum size when cropping with the mouse (you can crop down to about 10% of each dimension). You can get smaller than that by adjusting the “margins” sliders, but that’s rather complicated: they are calibrated in “% of full size” as cropped from the respective side. So getting an exact size at a selected position can get tricky.

Probably the easiest way is to do it in two steps: export an intermediate image at about twice the size you need as a png, then impor that and crop to final size, export as jpeg.

Or calculate the margins you need, set them numerically (right click on the sliders), then move the crop to the required position.

But I admit, both methods are not as easy as I’d like.

Siegfried · June 9, 2025, 4:10pm

This isn’t a 100% view of the scan, but rather a reduction. 1978x1319 (Darktable default) will be reduced to the desired 1200x800 during export.

Can you understand my goal?

Thank you!..Wooww thank you all for the fast answer!!!.. Thank you very much for your answers.

Siegfried · June 9, 2025, 5:08pm

I created an 8000x8000 section and exported it as an 8kx8k TIF.

I imported it back into Darktable, and now I can create and export 1200x800 sections.
This is similar to what “revietor” suggested with PNG files. Unfortunately, there’s no easier way

Thanks again for all your help!

Best regards
Siegfried

Donatzsky · June 9, 2025, 7:27pm

I recommend that you open a feature request/bug report on GitHub, asking to remove this limitation.