I want to create a Paint application with adjustable colors and brush radius using Trackbars.

edit

I have written the code for this as follows:

import cv2

import numpy as np

def nothing(x):
    pass

drawing = False # true if mouse is pressed

mode = True # if True, draw rectangle. Press 'm' to toggle to curve

ix,iy = -1,-1


def draw_circle(event,x,y,flags,param):
    global ix,iy,drawing,mode

    if event == cv2.EVENT_LBUTTONDOWN:
        drawing = True
        ix,iy = x,y

    elif event == cv2.EVENT_MOUSEMOVE:

        if drawing == True:
            if mode == True:
                cv2.rectangle(img,(ix,iy),(x,y),(0,255,0),-1)
            else:
                cv2.circle(img,(x,y),ra,(0,0,255),-1)

    elif event == cv2.EVENT_LBUTTONUP:
        drawing = False
        if mode == True:
            cv2.rectangle(img,(ix,iy),(x,y),(0,255,0),-1)
        else:
            cv2.circle(img,(x,y),ra,(0,0,255),-1)


img = np.zeros((1024,1024,3), np.uint8)

cv2.namedWindow('trackbar')

cv2.createTrackbar('Red','trackbar',0,255,nothing)

cv2.createTrackbar('Green','trackbar',0,255,nothing)

cv2.createTrackbar('Blue','trackbar',0,255,nothing)

cv2.createTrackbar('Radius','trackbar',10,200,nothing)

ra = 0

switch = '0 : OFF\n1 : ON'

cv2.createTrackbar(switch,'trackbar',0,1,nothing)

while(1):

    cv2.imshow('trackbar', img)
    ra = cv2.getTrackbarPos('Radius', 'trackbar')
    cv2.setMouseCallback('trackbar', draw_circle)
    k = cv2.waitKey(1) & 0xFF
    if k == ord('m'):
        mode = not mode
    elif k == 27:
        break

    r = cv2.getTrackbarPos('Red','trackbar')
    g = cv2.getTrackbarPos('Green', 'trackbar')
    b = cv2.getTrackbarPos('Blue', 'trackbar')
    s = cv2.getTrackbarPos(switch, 'trackbar')

    if s==0:
        img[:] = 0
    else:
        img[:] = [b,g,r]


cv2.destroyAllWindows()

But it is not working properly. Trackbar for changing RBG color is working but the circle and rectangle are not drawn on mouse click. Anyone can tell me what i am doing wrong in this code?