OpenCV TypeError Expected cv UMat for argument src - What is this

Question

Disclaimer  huge openCV noob     Traceback  most recent call last        File  lanes2 py   line 22  in   canny   canny lane image        File  lanes2 py   line 5  in canny  gray   cv2 cvtColor imgUMat  cv2 COLOR RGB2GRAY        TypeError  Expected cv  UMat for argument  src    What exactly is  src  referring to

User · Answer

src is the first argument to cv2 cvtColor  The error you are getting is because it is not the right form  cv2 Umat   is functionally equivalent to np float32    so your last line of code should read  gray   cv2 cvtColor np float32 imgUMat   cv2 COLOR RGB2GRAY

User · Answer

Sometimes I have this error when videostream from imutils package doesn t recognize frame or give an empty frame  In that case  solution will be figuring out why you have such a bad frame or use a standard VideoCapture 0  method from opencv2

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Is canny your own function  Do you use Canny from OpenCV inside it  If yes check if you feed suitable argument for Canny - first Canny argument should meet following criteria    type   lt type  numpy ndarray  gt  dtype  dtype  uint8   being single channel or simplyfing  grayscale  that is 2D array  i e  its shape should be 2-tuple of ints  tuple containing exactly 2 integers    You can check it by printing respectively  type variable name  variable name dtype variable name shape   Replace variable name with name of variable you feed as first argument to Canny

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The following can be used from numpy   import numpy as np  image   np array image

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I got round thid by writing reading to a file  I guessed cv imread would put it into the format it needed  This code for anki Vector SDK program but you get the idea   tmpImage   robot camera latest image raw image save  temp png   pilImage   cv imread  temp png

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Just add this at start      image   cv2 imread image

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Some dtype are not supported by specific OpenCV functions  For example inputs of dtype np uint32 create this error  Try to convert the input to a supported dtype  e g  np int32 or np float32

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gray   cv2 cvtColor cv2 UMat imgUMat   cv2 COLOR RGB2GRAY    UMat is a part of the Transparent API  TAPI  than help to write one code for the CPU and OpenCL implementations

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Not your code is the problem this is perfectly fine   gray   cv2 cvtColor imgUMat  cv2 COLOR RGB2GRAY    The problem is that imgUMat is None so you probably made a mistake when loading your image    imgUMat   cv2 imread  your image jpg     I suspect you just entered the wrong image path

User · Answer

that is referring to the expected dtype of your image   quot image quot  astype  float32   should solve your issue

User · Answer

This is a general error  which throws sometimes  when you have mismatch between the types of the data you use  E g I tried to resize the image with opencv  it gave the same error  Here is a discussion about it

[python] OpenCV TypeError: Expected cv::UMat for argument 'src' - What is this?

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