Certain images will report exception when generating greyscale_cam

[tvc5586]

Hello.

I encountered a issue with the generation of greyscale_cam (located in core.py). In short, some images will report exception "'int' object has no attribute 'backward'", while others won't. I found out that the problem is caused by the line that generates greyscale_cam.

The line originally looks like grayscale_cam = self.method(tensor, [self.target])
Even after changing the line to grayscale_cam = self.method(tensor.requires_grad_(), [self.target]) the problem still persists.

For records, I am using YOLOv8n.pt downloaded from Ultralytics and ISIC2019 dataset. The exception occurs when I try to use any method but "EigenCAM".

Hopefully a solution can be found as soon as possible.

[dev-rajk]

Thanks for raising the issue.
We have been caught up in a few exams for the past week. We will try to replicate the issue and resolve it at the earliest.

[Spritan]

@tvc5586 can you share the any eaxct image in ISIC2019 dataset as when i treidon randon=ms ample its w working fine.

[anastanescu]

I had the same issue with object detection, with images where there are no objects detected.
The source of the problem seems to be in line 137 in core.py, when no value of post_result is over the self.conf parameter. In this case, the result of the forward function remains an empty list (which is returned), causing the crash described above.