Feature Request: compare images not directly adjacent (in time) to one another

[alastairpotts]

Hi Saul,

Thanks again for a fantastic piece of software. Better than anything else I've ever tried, by far.

Background. I use camera traps to monitor plant and animal interactions; e.g. which animal is browsing on what plant (mostly plants that we've planted in a restoration landscape). We track the fate of individual plants in the images.

Problem. Monitoring herbivory on plants requires jumping across images that might not be directly next to each other, temporally. (e.g. herbivores are present during night shots, but we cannot see the plants, so we check the late afternoon image with the early morning image).

Request. It would be great if we could select two images that were not directly next to each to conduct the image differencing. It would be incredibly useful.

Hope this is something easy to implement.

Regards Alastair Potts

[saulgreenberg]

Hmm. This would be difficult to do. I also foresee issues with this. Image differencing subtracts similar pixels from the surrounding images that differ by more than a threshold. This works fairly well when images are taken together very close in time, as lighting and weather (and wind movement) are more or les similar across those images. However, when images are separated considerably in time, the changes between the images are much more dramatic. Thus the utility of image differencing is much more questionable.

Having said that, here is a way to do it. If you want to compare image in different intervals and if you can somehow tag them (leaving out tags on the uninteresting inbetween images), then you can do a custom select on that tag. This brings those images next to each other (as only those tagged images are displayed), and image differencing can be applied. And by the way, I do plan to put a Custom Selection on Time sometimes in the next few releases, although that will normally only return images inbetween a time range (regardless of the date). With that, you can )say) select an afternoon time, tag those, then select a morning time, and tag those as well. So when you custom select on that tag, you would get th

Does that make sense to you? If you have other questions, let me know. Also, its easier to contact me directly rather than through github - saul@ucalgary.ca