Zero.J's profile - activity

Hi berak,

Thank you so much! Your idea is totally work for me!

ok, thank you so much.

wow! cool! Let me try it. So the edited part just need simply add into my program or I have to write a new program to do?

Haha, ok. Thank you! And one more question, since my converting was correct. But when I try to do the cv2.inRange, I cannot do the mask very well. due to the lower and upper value was not set so good. So do you know any way can find out the Blue, Green or Red color's range?

Hi berak, So which is mean that my converting part was no problem right?

Hi everyone,

I'm just a beginner in OpenCV. I'm trying to find the green ball's center point in the image. But when I try to convert the image from BGR to HSV the shows image result will be change to another kind of color instead of the orignal image. This is the result image after the convertion:

Base on my simple understand it should not show this image results after the BGR to HSV. So does anyone know what's the problem cause my problem? Thank you!

Follow is my whole program:

#!/usr/bin/env python
# coding=utf-8

import sys
import rospy
import cv2
#import cv
import argparse
import numpy as np
from std_msgs.msg import String
from sensor_msgs.msg import Image
import std_srvs.srv


def image_processing (color):
    #image_src = cv2.imread('home/ros_ws/src/baxter_examples/ColorBalls.jpg',0)

    print ("deciding color...............")
    if color == "blue":
        lower = (86,31,4)
        upper = (220,88,50)

    if color == "green":
        lower = (29,30,20)
        upper = (64,255,255)

    if color == "red":
        lower = (17,15,100)
        upper = (50,56,200)

    print color

    image_hsv = cv2.cvtColor(image_resized,cv2.COLOR_BGR2HSV)
    cv2.imshow("or_image",image_hsv)
    cv2.waitKey(0)
    cv2.destroyAllWindows()
    image_mask = cv2.inRange(image_hsv,lower,upper)
    #cv2.imshow("or_image",image_mask)
    #cv2.waitKey(0)

    image_mask = cv2.erode(image_mask, None, iterations=2)
    image_mask = cv2.dilate(image_mask, None, iterations=2)
    cv2.imshow("or_image",image_mask)
    cv2.waitKey(0)

    print ("end maskingg")
    print ("finding center.........")

    contours, hierarchy = cv2.findContours(image_mask,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)
    if contours  is None:
        print ("cont is None")
    print ("len.........")
    print  len(contours)

    if len(contours) > 0:
        print  ("############################")
        print  len(contours)

        c =  max (contours,key=cv2.contourArea)
        ((x, y), radius) = cv2.minEnclosingCircle(c)
        M = cv2.moments(c)
        center = (int(M["m10"] / M["m00"]), int(M["m01"] / M["m00"]))

        print center

        if radius > 1:
            cv2.circle(image_resized, (int(x), int(y)), int(radius),(0, 255, 255), 2)
            cv2.circle(image_resized, center, 2, (0, 0, 255), -1)

def main():
    global ball_color
    global image_src
    global image_resized

    arg_fmt = argparse.RawDescriptionHelpFormatter
    parser = argparse.ArgumentParser(formatter_class=arg_fmt, description=main.__doc__)

    parser.add_argument(
        '-c','---color', dest='color',choices=['blue','green','red'], required=True,
        help= "the ball color to pick up", 
         )
    args=parser.parse_args()

    print ("Initializing...........................................")
    rospy.init_node("ylj_ballposition",anonymous=True)

    #image_src = cv2.imread('/home/ros_ws/src/baxter_examples/scripts/ColorBalls.JPG')
    print ("reading the image")
    image_src = cv2.imread('Balls.JPG')
    print ("readed..............")

    if image_src is None:
        print ("the image read is None............")

    #print ("show the image............")
    #cv2.imshow("or_image",image_src)
    #cv2.waitKey(0)

    print image_src.shape
    print ("resizing........")
    image_resized = cv2.resize(image_src,(400,300),interpolation = cv2.INTER_AREA)
    print image_resized.shape
    print ("resized........")

    #cv2.imshow("or_image",image_resized)
    #cv2.waitKey(0)

    print ("start image processing......")
    image_processing(args.color)

    cv2.imshow("image_processed",image_resized)
    cv2.waitKey(0)
    cv2.destroyAllWindows()

if __name__=='__main__':
    main()

Hi berak, I follow you idea and change the image reading path, then my problem was solved. Thank you for your advice.

oh, I found the method. It's just if image_src is None:

print ("the image read is None............")

And the showing result shows that it is None. It's that mean I didn't read the image?

Sorry....I had no idea about how to check the None or np.shape(img)==(). Would you mind teach me how to check it? or any website can find it?

I try add the :

print ("Initializing...........................................")
    rospy.init_node("ylj_ballposition",anonymous=True)
    image_src = cv2.imread('home/ros_ws/src/baxter_examples/ColorBalls.jpg')
    **print ("read the image....")**

Then will shows:

   Initializing...........................................
        read the image....
        deciding color...............
        blue
        OpenCV Error: Assertion failed ((scn == 3 || scn == 4) && (depth == CV_8U || depth == CV_32F)) in cvtColor, file /build/buildd/opencv-2.4.8+dfsg1/modules/imgproc/src/color.cpp, line 3959
        Traceback (most recent call last):

The rest of error message still same.

So what kind of print checks should I use? I kind of new in OpenCV would you mind give more detail things?Thank you

Hi everyone,

I'm a beginner and trying to use the basic OpenCV to find the choose color ball's center x,y value from the image. But When I try to run my program there had some error happen but I had no idea what's wrong in my program. Can anyone help me?

Follow is my progam:

#!/usr/bin/env python
# coding=utf-8

import sys
import rospy
import cv2
import cv

import argparse
import numpy as np
from std_msgs.msg import String
from sensor_msgs.msg import Image
import std_srvs.srv


def image_processing (color):
    #image_src = cv2.imread('home/ros_ws/src/baxter_examples/ColorBalls.jpg',0)

    print ("deciding color...............")
    if color == "blue":
        lower = (86,31,4)
        upper = (220,88,50)

    if color == "green":
        lower = (29,86,6)
        upper = (64,255,255)

    if color == "red":
        lower = (17,15,100)
        upper = (50,56,200)

    print color

    image_hsv = cv2.cvtColor(image_src,cv2.COLOR_BGR2HSV)##################
    image_mask = cv2.inRange(image_hsv,lower,upper)

    image_mask = cv2.erode(image_mask, None, iterations=2)
    image_mask = cv2.dilate(image_mask, None, iterations=2)

    print ("end maskingg")

    print ("finding center.........")

    contours,hierarchy = cv2.findContours(image_mask,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)[-2]

    if len(contours) > 0:

        c =  max (contours,key=cv2.contourArea)
        ((x, y), radius) = cv2.minEnclosingCircle(c)
        M = cv2.moments(c)
        center = (int(M["m10"] / M["m00"]), int(M["m01"] / M["m00"]))

        print center

        if radius > 1:

            cv2.circle(image_src, (int(x), int(y)), int(radius),(0, 255, 255), 2)

            cv2.circle(image_src, center, 2, (0, 0, 255), -1)

def main():
    global ball_color
    global image_src

    arg_fmt = argparse.RawDescriptionHelpFormatter
    parser = argparse.ArgumentParser(formatter_class=arg_fmt, description=main.__doc__)

    parser.add_argument(
        '-c','---color', dest='color',choices=['blue','green','red'], required=True,
        help= "the ball color to pick up", 
         )

    args=parser.parse_args()

    print ("Initializing...........................................")
    rospy.init_node("ylj_ballposition",anonymous=True)

    image_src = cv2.imread('home/ros_ws/src/baxter_examples/ColorBalls.jpg',1)

    image_processing(args.color)

    cv2.imshow("image_processed",image_src)

if __name__=='__main__':
    main()

This is the error message show:

Initializing...........................................
deciding color...............
blue
OpenCV Error: Assertion failed ((scn == 3 || scn == 4) && (depth == CV_8U || depth == CV_32F)) in cvtColor, file /build/buildd/opencv-2.4.8+dfsg1/modules/imgproc/src/color.cpp, line 3959
Traceback (most recent call last):
  File "/home/leddar/ros_ws/src/baxter_examples/scripts/ylj/ylj_imgball.py", line 101, in <module>
    main()
  File "/home/leddar/ros_ws/src/baxter_examples/scripts/ylj/ylj_imgball.py", line 91, in main
    image_processing(args.color)
  File "/home/leddar/ros_ws/src/baxter_examples/scripts/ylj/ylj_imgball.py", line 36, in image_processing
    image_hsv = cv2.cvtColor(image_src,cv2.COLOR_BGR2HSV)##################
cv2.error: /build/buildd/opencv-2.4.8+dfsg1/modules/imgproc/src/color.cpp:3959: error: (-215) (scn == 3 || scn == 4) && (depth == CV_8U || depth == CV_32F) in function cvtColor