A Python example for using Spectrico's car color classifier. It consists of object detector for finding the cars, and a classifier to recognize the colors of the detected cars. The object detector is an implementation of YOLOv3 (OpenCV DNN backend). It doesn't use GPU and one frame takes 1s to process on Intel Core i5-7600 CPU. YOLOv3 weights were downloaded from YOLO website. The classifier is based on Mobilenet v2 (TensorFlow backend). It takes 35 milliseconds on Intel Core i5-7600 CPU for single classification. It can be accelerated more by running on GPU and using batching. This classifier is not accurate enough yet and serves as a proof-of-concept demo.

This example takes an image as input, detects the cars using YOLOv3 object detector, crops the car images, makes them square while keeping the aspect ratio, resizes them to the input size of the classifier, and recognizes the color of each car. The result is shown on the display and saved as output.jpg image file.

Use --help to see usage of car_color_classifier_yolo3.py:

$ python car_color_classifier_yolo3.py --image cars.jpg

$ python car_color_classifier_yolo3.py [-h] [--yolo MODEL_PATH] [--confidence CONFIDENCE] [--threshold THRESHOLD] [--image]

required arguments:
  -i, --image              path to input image

optional arguments:
  -h, --help               show this help message and exit
  -y, --yolo MODEL_PATH    path to YOLO model weight file, default yolo-coco
  --confidence CONFIDENCE  minimum probability to filter weak detections, default 0.5
  --threshold THRESHOLD    threshold when applying non-maxima suppression, default 0.3

• python
• numpy
• tensorflow
• opencv
• yolov3.weights must be downloaded from https://pjreddie.com/media/files/yolov3.weights and saved in folder yolo-coco

The settings are stored in python file named config.py:

model_file = "model-weights-spectrico-car-colors-mobilenet-224x224-052EAC82.pb"
label_file = "labels.txt"
input_layer = "input_1"
output_layer = "softmax/Softmax"
classifier_input_size = (224, 224)

model_file is the path to the car color classifier classifier_input_size is the input size of the classifier label_file is the path to the text file, containing a list with the supported colors

The examples are based on the tutorial by Adrian Rosebrock: YOLO object detection with OpenCV The YOLOv3 object detector is from: YOLO: Real-Time Object Detection

@article{yolov3,
  title={YOLOv3: An Incremental Improvement},
  author={Redmon, Joseph and Farhadi, Ali},
  journal = {arXiv},
  year={2018}
}

The car color classifier is based on MobileNetV2 mobile architecture: MobileNetV2: Inverted Residuals and Linear Bottlenecks