I’m new to Darktable, and in the process of testing it out I have noticed the following problem:
When I use the excellent module “perspective correction” and choose “automatic fit , horizontal and vertical” with “automatic cropping off” the dimension of the viewing panel sometimes becomes the new “original image format” (if the image needs a lot of adjustment). In the “crop and rotate” module you are then not able to crop the image to the original aspect ratio unless you know what this is and the aspect ratio can be found in the drop down list.
In the “perspective correction” module you can choose to crop to “original format” and this works ok but the crop can’t be changed in any way (reduced in size and moved) and you are then stuck with a crop you don’t want.
But isn’t it a bug that the perspective correction module changes the aspect ratio of the image if it is not cropped?
In my view the output of the module should always be an image in the original aspect ratio. Part of the image would then be “black” that is without any information from the original image. This image can then easily be cropped in the crop and rotate module maintaining or changing the aspect ratio. This is how RawTherapee works.
Exported form DT after persp. correction, automatic cropping off: 3778x2620, aspect ratio: 1.44
What causes this change in aspect ratio?
Well perspective correction ? I’m not sure what you expect. If you do perspective correction you are changing the aspect of the image! Take a picture, activate perspective correction, in the vertical correction force -1 for example. The image will look flat, almost 16:9. There is no way around that. And RawTherappee cannot do otherwise or some black area are added at the top of the picture.
Thank you for a fast response, but I think there is a misunderstanding somewhere.
When automatic cropping is off I expected an output from the perspective module in the original aspect ratio of 1.33 but with some black areas added just like you described in your previous response option 1.
Put in other words how can I enable the first option you describe: “no crop - aspect ratio is kept but you have some black borders (unavoidable)”?
Oups! I didn’t meant that, wrote to quick. This is not possible. As said above, when perspective correction is done the aspect ratio cannot be kept. Sorry for the confusion.
Oh I see, it works as intended. Actually the manual doesn’t say what happens when cropping is off.
RT and Photoshop Elements keeps the aspect ratio. So I was convinced without giving it much thought that this would the case in DT as well (it’s just a matter of adding black areas where needed).
And I have just implemented a way to move the crop (when aspect ratio is constraint) to the desired location making recomposing easy and without requiring to use crop&rotate.
? I’m not sure what you expect. If you do perspective correction you are changing the aspect of the image! Take a picture, activate perspective correction, in the vertical correction force -1 for example. The image will look flat, almost 16:9. There is no way around that. And RawTherappee cannot do otherwise or some black area are added at the top of the picture.