A bug in python api getImgIds when the input parameters catIds is a list

[xuchao1688]

at line 197, the function try to travel around all the category in catIds and collect the results of every category avoiding repeating results in imgIds. However you use a '&=' operation instead of '|=' operation, which causes the result to be null or less than expected regardless of imgIds when the length of catIds list is more than 1.

[xuchao1688]

I am looking forward to hearing back from you soon.

[salihkaragoz]

It works properly. You missed some point.

&= operant means intersection
|= operant means combination
the method returns image ids which have specific classes.
For example;
dataset = {10, 20, 30, 40, 50, 60, 70}
class_1 = {20,40,50,60}
class_2 = {40,50,60}
the method returns intersection of two classes, namely the method returns
getImgIds([class_1, class_2]) ---> {40,50,60}
getImgIds([class_2, class_1]) ---> {40,50,60} doesn't matter which one is first
that means each image must have both classes.

you can see which number represent a class with this link
you can look with this code;

from pycocotools.coco import COCO
cat_Ids=[23,22]
tann = COCO('instances_train2017.json')
vann = COCO('instances_val2017.json')
print len(tann.getImgIds(catIds=cat_Ids)+vann.getImgIds(catIds=cat_Ids))

also you can compare and check in the cocodataset_explore

[xuchao1688]

Thanks for your reply (*≧ω≦)

[maria-mh07]

In my code:
from pycocotools.coco import COCO coco=COCO('cocoapi/annotations/instances_val2014.json') catIds=coco.getCatIds(catNms=['traffic light','stop sign','mouse','keyboard','cell phone']) imgIds=coco.getImgIds(catIds=catIds)
where catIds=[10,13,74,76,77] but imgIds=[] with len(imgIds)=0
I don't understand why this happens. When I write only one category, for example catNms=['traffic light'], it works.