How to Apply Mask to Image in OpenCV

Question

I want to apply a binary mask to a color image  Please provide a basic code example with proper explanation of how the code works  Also  is there some option to apply a mask permanently so all functions operate only within the mask

User · Answer

While  perrejba s answer is correct  it uses the legacy C-style functions  As the question is tagged C    you may want to use a method instead   inputMat copyTo outputMat  maskMat    All objects are of type cv  Mat   Please be aware that the masking is binary  Any non-zero value in the mask is interpreted as  do copy   Even if the mask is a greyscale image   Also be aware that the  copyTo   function does not clear the output before copying   If you want to permanently alter the original Image  you have to do an additional copy clone assignment  The copyTo   function is not defined for overlapping input output images  So you can t use the same image as both input and output

User · Answer

Well  this question appears on top of search results  so I believe we need code example here  Here s the Python code  import cv2  def apply mask frame  mask        quot  quot  quot Apply binary mask to frame  return in-place masked image  quot  quot  quot      return cv2 bitwise and frame  frame  mask mask   Mask and frame must be the same size  so pixels remain as-is where mask is 1 and are set to zero where mask pixel is 0  And for C   it s a little bit different  cv  Mat inFrame     Original  non-empty  image cv  Mat mask     Original  non-empty  mask          cv  Mat outFrame      Result output inFrame copyTo outFrame  mask

User · Answer

You don t apply a binary mask to an image  You  optionally  use a binary mask in a processing function call to tell the function which pixels of the image you want to process  If I m completely misinterpreting your question  you should add more detail to clarify

User · Answer

You can use the mask to copy only the region of interest of an original image to a destination one   cvCopy origImage destImage mask     where mask should be an 8-bit single channel array   See more at the OpenCV docs

User · Answer

Here is some code to apply binary mask on a video frame sequence acquired from a webcam  comment and uncomment the  bitwise not Mon mask Mon mask   line and see the effect   bests  Ahmed    include  cv h          include it to used Main OpenCV functions   include  highgui h    include it to use GUI functions   using namespace cv  using namespace std   int main int argc  char   argv        int c   int radius 100        CvPoint2D32f center        IplImage  color img        Mat image  image0 image1           IplImage  tmp      CvCapture  cv cap   cvCaptureFromCAM 0        while 1             tmp   cvQueryFrame cv cap      get frame              IplImage to Mat             Mat imgMat tmp               image  tmp          center x   tmp- gt width 2      center y   tmp- gt height 2            Mat Mon mask image size    CV 8UC1  Scalar 0 0 0              circle Mon mask  center  radius  Scalar 255 255 255   -1  8  0      -1 means filled          bitwise not Mon mask Mon mask     comment   ou pas   RP ou DMLA               if tmp    0              imshow  Glaucom   image      show frame       c   cvWaitKey 10      wait 10 ms or for key stroke     if c    27          break     if ESC  break and quit              clean up        cvReleaseCapture   amp cv cap        cvDestroyWindow  Glaucom

[c++] How to Apply Mask to Image in OpenCV?

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