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Raspberry Pi + Webcam + Python + OpenCV = Weird Problems + No Solutions

Former Member

Now,

 

EDIT: Main goal, capture an image, wait some time, capture another image, add the two images together and show it :END EDIT

 

I run the program and can see the webcam feed, I then press a key capturing an image as img1, then again but as img2, and again img3. Now when the final image displays (img2+img3) it just shows img3 added to itself, i.e. as though I coded Add(img3,img3,img1). I have also tried AddWeighted and AND functions.

 

I have tried and tried and cannot find the problem, is it the Add function that is not reading img2, or could img2 not be saved properly? or what is going on!!

 

Any help would be great,

 

Cheers,

 

Dan.

 

 

# Daniel Myers
# cvTest.py
# 18 Feb 13

 

from cv import *

 

SIZE=(HEIGHT,WIDTH)=(640,480) # Image capture size
CAMERA_INDEX=-1 # -1 means any camera attached

 

def TakePic(cam):
    NamedWindow('cvTest',CV_WINDOW_AUTOSIZE)
    while True:
        img=QueryFrame(cam)
        ShowImage('cvTest',img)
        k=WaitKey(2)
        if k>=0:
            return img

 

cam=CaptureFromCAM(CAMERA_INDEX) # Initializes capturing a video from a camera
SetCaptureProperty(cam,CV_CAP_PROP_FRAME_WIDTH,WIDTH) # Set the capture image width
SetCaptureProperty(cam,CV_CAP_PROP_FRAME_HEIGHT,HEIGHT) # Set the capture image height

 

img1=TakePic(cam)
ShowImage('img1',img1)

 

img2=TakePic(cam)
ShowImage('img2',img2)

 

img3=TakePic(cam)
ShowImage('img3',img3)

 

AddWeighted(img2,0.4,img3,0.6,20,img1)
ShowImage('img2+img3',img1)

 

k=WaitKey(100000)
DestroyAllWindows()
del(cam)

Parents

  • Wrote two functions (below). I capture an image, convert to mat, capture an image, convert to mat, add the two mats, convert to image and show..... now this works, it shows overlapped images however this is awful coding and terribly slow, but proves the Add function works, and the theory is there there is jsut something wrong with the IplImage's

     

    def Img2Mat(img):
         width=img.width
         height=img.height
         depth=img.depth
         mat=CreateMat(height,width,depth)
         for w in range(0,width):
              for h in range(0,height):
                   value=Get2D(img,h,w)
                   Set2D(mat,h,w,value)

         return mat

    def Mat2Img(mat):
         width=mat.cols
         height=mat.rows
         size=(width,height)
         img=CreateImage(size,8,3)
         for w in range(0,width):
               for h in range(0,height):
                    value=Get2D(mat,h,w)
                    Set2D(img,h,w,value)
         return img

Reply

  • Wrote two functions (below). I capture an image, convert to mat, capture an image, convert to mat, add the two mats, convert to image and show..... now this works, it shows overlapped images however this is awful coding and terribly slow, but proves the Add function works, and the theory is there there is jsut something wrong with the IplImage's

     

    def Img2Mat(img):
         width=img.width
         height=img.height
         depth=img.depth
         mat=CreateMat(height,width,depth)
         for w in range(0,width):
              for h in range(0,height):
                   value=Get2D(img,h,w)
                   Set2D(mat,h,w,value)

         return mat

    def Mat2Img(mat):
         width=mat.cols
         height=mat.rows
         size=(width,height)
         img=CreateImage(size,8,3)
         for w in range(0,width):
               for h in range(0,height):
                    value=Get2D(mat,h,w)
                    Set2D(img,h,w,value)
         return img

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