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问题:
I'm currently in Ubuntu 14.04, using python 2.7 and cv2.
When I run this code:
import numpy as np import cv2 img = cv2.imread('2015-05-27-191152.jpg',0) gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
it returns:
File "face_detection.py", line 11, in gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) cv2.error: /home/arthurckl/Desktop/opencv-3.0.0-rc1/modules/imgproc/src/color.cpp:7564: error: (-215) scn == 3 || scn == 4 in function cvtColor
I already searched here and one answer said that I could be loading my photo the wrong way, because it should have 3 dimensions: rows, columns and depth.
When I print the img.shape it returns only two numbers, so I must be doing it wrong. But I don't know the right way to load my photo.
回答1:
Give the full path of image with forward slash. It solved the error for me.
E.g.
import numpy as np import cv2 img = cv2.imread('C:/Python34/images/2015-05-27-191152.jpg') gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
Also, if you give 0 in second parameter while loading image using cv2.imread than no need to convert image using cvtColor, it is already loaded as grayscale image eg.
import numpy as np import cv2 gray = cv2.imread('C:/Python34/images/2015-05-27-191152.jpg',0)
回答2:
Please Set As Below
img = cv2.imread('2015-05-27-191152.jpg',1) // Change Flag As 1 For Color Image //or O for Gray Image So It image is //already gray
回答3:
Only pass name of the image, no need of 0:
img=cv2.imread('sample.jpg')
回答4:
img = cv2.imread('2015-05-27-191152.jpg',0)
The above line of code reads your image in grayscale color model, because of the 0 appended at the end. And if you again try to convert an already gray image to gray image it will show that error.
So either use above style or try undermentioned code:
img = cv2.imread('2015-05-27-191152.jpg') gray_img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
回答5:
First thing you should check is that whether the image exists in the root directory or not. This is mostly due to image with height = 0. Which means that cv2.imread(imageName) is not reading the image.
回答6:
Here is what i observed when I used my own image sets in .jpg format. In the sample script available in Opencv doc, note that it has the undistort and crop the image lines as below:
# undistort dst = cv2.undistort(img, mtx, dist, None, newcameramtx) # crop the image x,y,w,h = roi dst = dst[y:y+h, x:x+w] cv2.imwrite('calibresult.jpg',dst)
So, when we run the code for the first time, it executes the line cv2.imwrite('calibresult.jpg',dst) saving a image calibresult.jpg in the current directory. So, when I ran the code for the next time, along with my sample image sets that I used for calibrating the camera in jpg format, the code also tried to consider this newly added image calibresult.jpg due to which the error popped out
error: C:\builds\master_PackSlaveAddon-win64-vc12-static\opencv\modules\imgproc\src\color.cpp:7456: error: (-215) scn == 3 || scn == 4 in function cv::ipp_cvtColor
What I did was: I simply deleted that newly generated image after each run or alternatively changed the type of the image to say png or tiff type. That solved the problem. Check if you are inputting and writing calibresult of the same type. If so, just change the type.
回答7:
i think it because cv2.imread cannot read .jpg picture,you need changed .jpg to .pgn,ma
回答8:
I've had this error message show up, for completely unrelated reasons to the flags 0 or 1 mentionned in the other answers. You might be seeing it too because cv2.imread will not error out if the path string you pass it is not an image:
In [1]: import cv2 ...: img = cv2.imread('asdfasdf') # This is clearly not an image file ...: gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) ...: OpenCV Error: Assertion failed (scn == 3 || scn == 4) in cv::cvtColor, file C:\projects\opencv-python\opencv\modules\imgproc\src\color.cpp, line 10638 --------------------------------------------------------------------------- error Traceback (most recent call last) in () 1 import cv2 2 img = cv2.imread('asdfasdf') # This is clearly not an image file ----> 3 gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) error: C:\projects\opencv-python\opencv\modules\imgproc\src\color.cpp:10638: error: (-215) scn == 3 || scn == 4 in function cv::cvtColor
So you're seeing a cvtColor failure when it's in fact a silent imread error. Keep that in mind next time you go wasting an hour of your life with that cryptic metaphor.
Solution
You might need to check that your path string represents a valid file before passing it to cv2.imread:
import os def read_img(path): """Given a path to an image file, returns a cv2 array str -> np.ndarray""" if os.path.isfile(path): return cv2.imread(path) else: raise ValueError('Path provided is not a valid file: {}'.format(path)) path = '2015-05-27-191152.jpg' img = read_img(path) gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
Written this way, your code will fail gracefully.
回答9:
This answer if for the people experiencing the same problem trying to accessing the camera.
import numpy as np import cv2 cap = cv2.VideoCapture(0) while(True): # Capture frame-by-frame ret, frame = cap.read() # Our operations on the frame come here gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY) # Display the resulting frame cv2.imshow('frame',gray) if cv2.waitKey(1) & 0xFF == ord('q'): break # When everything done, release the capture cap.release() cv2.destroyAllWindows()
Using Linux:
if you are trying to access the camera from your computer most likely there is a permission issue, try running the python script with sudo it should fix it.
sudo python python_script.py
To test if the camera is accessible run the following command.
ffmpeg -f v4l2 -framerate 25 -video_size 640x480 -i /dev/video0 output.mkv
回答10:
Try this at line 11, worked for me.I think you're missing the parameters of function detectMultiScale()
faces = face_cascade.detectMultiScale(gray, 1.3, 5)
