Python3 samples/dnn/object_detection.py. OpenCV-tutorial on YOLOv3 does not work

[NobuoTsukamoto]

System information (version)

• OpenCV => 3.4.2
• Operating System / Platform => Fedora 28
• Compiler => GCC 8.1
• Python3 => 3.6.6

Detailed description

I tried to do the Python3 OpenCV-Sample on yolov3.
I executed opencv/samples/dnn/object_detection.py. (https://github.com/opencv/opencv/blob/3.4.2/samples/dnn/object_detection.py)
But it did not work with errors(TypeError: integer argument expected, got float).

I executed the following command.
"""python3 object_detection.py --input=./test.jpg --model=./yolov3.weights --config=./yolov3.cfg --classes=./object_detection_classes_coco.txt --scale=0.00392 --width=416 --height=416
"""

All errors are below.
'''Traceback (most recent call last):
File "object_detection.py", line 196, in
postprocess(frame, outs)
File "object_detection.py", line 162, in postprocess
drawPred(classIds[i], confidences[i], left, top, left + width, top + height)
File "object_detection.py", line 73, in drawPred
cv.rectangle(frame, (left, top), (right, bottom), (0, 255, 0))
TypeError: integer argument expected, got float
'''

I guess that in Python 3 the following operation result is a floating point number, not an integer.
https://github.com/opencv/opencv/blob/3.4.2/samples/dnn/object_detection.py#L145-L146

[alalek]

Perhaps this should work:
cv.rectangle(frame, (int(left), int(top)), (int(right), int(bottom)), (0, 255, 0))

[dkurt]

Or these two lines:

left = int(center_x - width / 2)
top = int(center_y - height / 2)

[NobuoTsukamoto]

I fixed object_detection.py. And it worked fine.

left = int(center_x - width / 2)
top = int(center_y - height / 2)

I would like to send a pull request.

Thank you very much.

[alalek]

Perhaps this work too (// - integer division):

left = center_x - width // 2

Feel free to prepare PR into 3.4 branch.