【OpenCV - Python】：使用createTrackbar创建滑动条

• 1. 相关函数
• 2. 单个滑动条
• 3. 多个滑动条
• 4. 参考资料

• createTrackbar

// 创建一个滑动条并将其附加到指定的窗口
int cv::createTrackbar(const String & 	  trackbarname, // 滑动条名称
					   const String & 	  winname,      // 窗口名称
					   int * 	          value,        // 滑动条初始位置
					   int 	              count,        // 滑动条最大值
					   TrackbarCallback   onChange = 0, // 回调函数
					   void * 	          userdata = 0)	

• getTrackbarPos

// 获取特定滑动条的当前滑动块位置
int cv::createTrackbar(const String & 	  trackbarname, // 滑动条名称
					   const String & 	  winname)      // 窗口名称

线性叠加两张图像：

import cv2

max_alpha = 100
window_name = 'Linear blend'

src1 = cv2.imread('1.jpg')
src2 = cv2.imread('2.jpg')

# 回调函数
def update_alpha(x):
    alpha = x / max_alpha
    beta = 1.0 - alpha
    dst = cv2.addWeighted(cv2.resize(src1, (330,186)), alpha, src2, beta, 0)
    cv2.imshow(window_name, dst)

cv2.namedWindow(window_name)
cv2.createTrackbar('Alpha', window_name, 0, max_alpha, update_alpha)

cv2.waitKey(0)

改变图像对比度和亮度：

import cv2
import numpy as np

# 单个回调函数无法同时获取两个Trackbar的滑动块位置，定义一个返回pass的回调函数即可
def nothing(x):
    pass

window_name = 'contrast_brightness'
image = cv2.imread('2.jpg')
cv2.imshow('Original image', image)

cv2.namedWindow(window_name)
cv2.createTrackbar('contrast', window_name, 0, 300, nothing)
cv2.createTrackbar('brightness', window_name, 0, 255, nothing)

while True:
	# 使用getTrackbarPos函数分别获取对比度和亮度值
    contrast = cv2.getTrackbarPos('contrast', window_name)
    brightness = cv2.getTrackbarPos('brightness', window_name)
    new_image = cv2.convertScaleAbs(image, contrast*0.01, brightness)
    cv2.imshow(window_name, new_image)
    k = cv2.waitKey(1) & 0xFF
    if k == 27:
        break

https://docs.opencv.org/4.x/d9/dc8/tutorial_py_trackbar.html