opencv 错误：（-215：断言失败）size.width>0 && size.height>0 in function 'cv::imshow'

Question

I wanna crop the image within the coordinates of rectangle from object detection. Are there any problems in my x,y coordinates? The rectangle can be drawn but the image cannot be cropped.

import cv2 
import numpy as np 

image = cv2.imread('venv/img.jpg')

classNames = []
classFile = 'coco.names'
with open(classFile,'rt') as f:
    classNames = f.read().rstrip('n').split('n')

configPath = 'ssd_mobilenet_v3_large_coco_2020_01_14.pbtxt'
weightsPath = 'frozen_inference_graph.pb'

net = cv2.dnn_DetectionModel(weightsPath, configPath)
net.setInputSize(320, 320)
net.setInputScale(1.0 / 127.5)
net.setInputMean((127.5, 127.5, 127.5))
net.setInputSwapRB(True)

classIds, confs, bbox = net.detect(image, confThreshold=0.5)

print(classIds, bbox)
if len(classIds) != 0:
    for classId, confidence, box in zip(classIds.flatten(), confs.flatten(), bbox):
        cv2.rectangle(image, box, color=(0, 255, 0), thickness=2)
        print(bbox)
        x1=box[0]
        y1=box[1]
        x2=box[2]
        y2=box[3]
        crop_person = image[y1:y2,x1:x2]
        cv2.imshow('img',crop_person)
        cv2.waitKey(0)


image = cv2.resize(image,(480,640))
cv2.imshow('img',image)
cv2.waitKey(0)

the result of printing bbox is shown below:

[[384 617 218 731]
 [ 45 722 188 472]
 [568 648 251 622]
 [767 691 165 528]
 [888 615 131 537]
 [232 657 187 545]
 [ 27 598 128 475]
 [168 590  98 169]
 [782 573 137 301]
 [795 667 186 499]
 [150 717 117 472]
 [227 628 312 672]]

So,I think the coordinates in the bbox can be used directly.

Answer 1

Print the Xs and Ys, see if they didn't create a 0 area rectangle. You can also change the imshow part to be:

if (y2-y1)*(x2-x1) > 0:
  cv2.imshow(....)

Also, make sure that y2 is actually greater than y1 (same goes to x).