图像处理笔记（5）---- OpenCV 用滑动条做调色板

import numpy as np
import cv2 as cv

def nothing(x):
    pass


drawing = False #如果按下鼠标，则为真
mode = True #如果为真，绘制矩形。按m键可以切换到曲线
ix,iy = -1,-1
#鼠标回调函数
def draw_circle(event, x, y, flags, param):
    r = cv.getTrackbarPos('R','image')
    g = cv.getTrackbarPos('G','image')
    b = cv.getTrackbarPos('B','image')
    color = (b,g,r)
    
    global ix,iy,drawing,mode
    if event == cv.EVENT_LBUTTONDOWN:
        drawing = True
        ix,iy = x,y
    #当鼠标左键按下并移动是绘制图形。event可以查看移动，flags查看是否按下
    elif event == cv.EVENT_MOUSEMOVE and flags == cv.EVENT_FLAG_LBUTTON:
        if drawing == True:
            if mode == True:
                cv.rectangle(img, (ix,iy), (x,y), color, -1)
            else:
                r = int(np.sqrt((x - ix)**2 + (y - iy)**2))
                cv.circle(img,(x,y), r, color, -1)
    #当鼠标松开停止绘画      
    elif event == cv.EVENT_LBUTTONUP:
        drawing = False
        if mode == True:
            cv.rectangle(img, (ix,iy),(x,y),color,-1)
        else:
            cv.circle(img,(x,y),abs(x-ix),color,-1)


        
#创建一副黑色图像
img = np.zeros((512,512,3),np.uint8)
cv.namedWindow('image')

cv.createTrackbar('R','image',0,255,nothing)
cv.createTrackbar('G','image',0,255,nothing)
cv.createTrackbar('B','image',0,255,nothing)
cv.setMouseCallback('image', draw_circle)

while(1):
    cv.imshow('image', img)
    if cv.waitKey(1) & 0xFF == 27:
        break
    elif cv.waitKey(1) & 0xFF == ord('m'):
        mode = not mode
        
cv.destroyAllWindows()