Beginner's notes on Tensorflow opencv

OpenCV expansion training sample

If you want to train an object detector from scratch and ensure the correctness, you need a lot of samples. If you don't want to use others' encapsulated samples, you need to make positive and negative samples to take pictures and delineate the area. This process is a bit too boring, so you want to use OpenCV to carry out simple graphic transformation and get multiple training samples in a short time. Here are some simple transformation methods and sample code.


Here is a simple random clipping code

import cv2
import cv2
import random
img = cv2.imread("2.jpg")
width,height,depth = img.shape
img_width_box = int(width * 0.2) #Tailoring size
img_height_box = int(height * 0.2)
for i in range(9):  #9 clipping
    X = int(random.uniform(0, width * 0.8))
    Y = int(random.uniform(0, height * 0.8))
    copyImg = img[X:X+img_width_box,Y:Y+img_height_box]


If you do not want to change the size of training samples, you can expand the database file by random rotation transformation.

import cv2
img = cv2.imread("2.jpg")
rows,cols,depth = img.shape
#Using the getRotationMatrix2D function, the first parameter is the rotation center, the second is the counterclockwise rotation angle, and the third is the scaling factor
img_change = cv2.getRotationMatrix2D((cols/2,rows/2),45,1)
#Image recompression and reality using warpAffine function
res = cv2.warpAffine(img,img_change,(rows,cols))

But the rotation of this code will cause incomplete display of the image

Random transformation of image color

Change the hue, saturation and brightness of the image to enlarge the sample

import cv2
import numpy as np
img = cv2.imread("2.jpg")
img_hsv = cv2.cvtColor(img,cv2.COLOR_BGR2HSV)
turn_green_hsv = img_hsv.copy()
turn_green_hsv[:,:,0] = (turn_green_hsv[:,:,0] + np.random.random())%180
turn_green_hsv[:,:,1] = (turn_green_hsv[:,:,1] + np.random.random())%180
turn_green_hsv[:,:,2] = (turn_green_hsv[:,:,2] + np.random.random())%180
turn_green_img = cv2.cvtColor(turn_green_hsv,cv2.COLOR_HSV2BGR)

In order to add some noise to the image, the transformed image can also be Gamma transformed

Mouse monitoring

Finally, OpenCV is used to monitor the mouse so as to mark the target position easily. Of course, labelimg can also be used to process the training image

This is a code that uses the mouse to circle the target object (drawing has no drag effect, if you need to get a good drawing experience, you can use CV2 "event" flag "lbutton (drag with the left key to achieve)

import cv2
rect_start = (0,0)
rect_end = (0,0)   #Initialize box area diagonal vertex coordinates
def on_mouse(event,x,y,flags,param):
    global rect_start 
    global rect_end    

    if event == cv2.EVENT_LBUTTONDOWN:
        rect_start = (x,y)
    elif event == cv2.EVENT_LBUTTONUP:
        rect_end = (x,y)

img = cv2.imread("2.jpg")

    if cv2.waitKey(1) & 0xFF == ord('q'):

This is the end of OpenCV learning. If there is any need later, continue to study

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Tags: OpenCV Database

Posted on Mon, 03 Feb 2020 09:54:19 -0500 by spacee