ImgAnnot is an app used for annotation of images for computer vision tasks.
Annotation Types it supports are:
Bounding Boxes
Polygons
Ellipses and Circles
Points
Lines(Still Experimental)
It supports its own custom annotation format and popular annotation formats like:
Coco annotation format
Pascal Voc annotation format.
It also has an auto-continue feature, such that the app can be closed and when revisited again, the user can continue from where the annotation was ended.
Tutorials on how to use it is available at https://youtube.com/playlist?list=PLI-AKnb1teYs5GqMvo4dff6vLbIVJPLMN