Python下使用OpenCV——使用Trackbar实现绘图板

本次实验利用到了cv2中的createTrackbar和getTrackbarPos函数实现一个绘图板的功能，用户可以选择矩形或是画笔模式，并设置调色板中的值来选择颜色，再选择画笔大小，进行绘图。除此之外，还可以用橡皮擦进行擦除，模式同样也分为矩形和画笔。下面是具体的代码：

import cv2
import numpy as np

drawing = False
mode = True
ix, iy = -1, -1

def nothing(x):
pass

def draw_circle(event,x,y,flags,param):
    r = cv2.getTrackbarPos('R','image')
    g = cv2.getTrackbarPos('G','image')
    b = cv2.getTrackbarPos('B','image')
    color = (b,g,r)
if s == 1:
        color = (255,255,255)

    s = cv2.getTrackbarPos('eraser','image')
    thin = cv2.getTrackbarPos('thin','image')

global ix,iy,drawing,mode
if event == cv2.EVENT_LBUTTONDOWN:
        drawing = True
        ix,iy = x,y
elif event == cv2.EVENT_MOUSEMOVE and flags == cv2.EVENT_FLAG_LBUTTON:
if drawing == True:
if mode == True:
                cv2.rectangle(img, (ix,iy),(x,y),color,-1)
else:
                cv2.circle(img,(x,y),thin,color,-1)
elif event == cv2.EVENT_LBUTTONUP:
        drawing == False

img = np.zeros((512,512,3), np.uint8)
img[:] = 255
cv2.namedWindow('image')
cv2.createTrackbar('R','image',0,255,nothing)
cv2.createTrackbar('G','image',0,255,nothing)
cv2.createTrackbar('B','image',0,255,nothing)

cv2.createTrackbar('eraser','image',0,1,nothing)
cv2.createTrackbar('thin','image',1,50,nothing)

cv2.setMouseCallback('image', draw_circle)

while(1):
    cv2.imshow('image',img)
    k = cv2.waitKey(1) & 0xFF
if k == ord('m'):
        mode = not mode
elif k == 27:
break

下面是运行的结果：
1.运行初始界面

2.选择颜色分别进行矩形绘图和画笔绘图，此图中的画笔的大小为1

3.此时的画笔大小为15

4.使用大小为15的橡皮擦擦除面板（选择了画笔模式的橡皮擦）

5.使用大小为4的橡皮擦擦除面板（选择了画笔模式的橡皮擦）