Combining Two Images with OpenCV

Question

I m trying to use OpenCV 2 1 to combine two images into one  with the two images placed adjacent to each other  In Python  I m doing   import numpy as np  cv  img1   cv LoadImage fn1  0  img2   cv LoadImage fn2  0   h1  w1   img1 height img1 width h2  w2   img2 height img2 width    Create an array big enough to hold both images next to each other  vis   np zeros  max h1  h2   w1 w2   np float32   mat1   cv CreateMat img1 height img1 width  cv CV 32FC1  cv Convert  img1  mat1    mat2   cv CreateMat img2 height  img2 width  cv CV 32FC1  cv Convert  img2  mat2      Copy both images into the composite image  vis  h1   w1    mat1 vis  h2  w1 w1 w2    mat2  h w   vis shape vis2   cv CreateMat h  w  cv CV 32FC3  vis0   cv fromarray vis  cv CvtColor vis0  vis2  cv CV GRAY2BGR  cv ShowImage  test   vis2  cv WaitKey     The two input images are   https   code ros org trac opencv browser trunk opencv samples c box png rev 2270  https   code ros org trac opencv browser trunk opencv samples c box in scene png rev 2270  The resulting image is     It may be hard to distinguish from the rest of the site  but most of the image is white  corresponding to where the individual images should be  The black area is where no image data was written   Why is all my image data being converted to white

User · Answer

For those who are looking to combine 2 color images into one   this is a slight mod on Andrey s answer which worked for me    img1   cv2 imread imageFile1  img2   cv2 imread imageFile2   h1  w1   img1 shape  2  h2  w2   img2 shape  2    create empty matrix vis   np zeros  max h1  h2   w1 w2 3   np uint8    combine 2 images vis  h1   w1  3    img1 vis  h2  w1 w1 w2  3    img2

User · Answer

For cases where your images happen to be the same size  which is a common case for displaying image processing results   you can use numpy s concatenate to simplify your code   To stack vertically  img1 over img2    vis   np concatenate  img1  img2   axis 0    To stack horizontally  img1 to the left of img2    vis   np concatenate  img1  img2   axis 1    To verify   import cv2 import numpy as np img1   cv2 imread  img1 png   img2   cv2 imread  img2 png   vis   np concatenate  img1  img2   axis 1  cv2 imwrite  out png   vis    The out png image will contain img1 on the left and img2 on the right

User · Answer

You can also use OpenCV s inbuilt functions cv2 hconcat and cv2 vconcat which like their names suggest are used to join images horizontally and vertically respectively   import cv2  img1   cv2 imread  opencv lena jpg   img2   cv2 imread  opencv baboon jpg    v img   cv2 vconcat  img1  img2   h img   cv2 hconcat  img1  img2    cv2 imshow  Horizontal   h img  cv2 imshow  Vertical   v img  cv2 waitKey 0  cv2 destroyAllWindows     Horizontal Concatenation    Vertical Concatenation

User · Answer

The three best way to do it using a single line of code import cv2 import numpy as np    img   cv2 imread  Imgs Saint Roch new data Point 4 Face jpg   dim    256  256  resizedLena   cv2 resize img  dim  interpolation   cv2 INTER LINEAR  X  Y   resizedLena  resizedLena    Methode 1  Using Numpy  hstack  vstack  Fusion Horizontal   np hstack  resizedLena  Y  X   Fusion Vertical     np vstack  newIMG  X    cv2 imshow  Fusion Vertical using vstack   Fusion Vertical  cv2 waitKey 0     Methode 2  Using Numpy  contanate  Fusion Vertical     np concatenate  resizedLena  X  Y   axis 0  Fusion Horizontal   np concatenate  resizedLena  X  Y   axis 1   cv2 imshow  quot Fusion Horizontal usung concatenate quot   Fusion Horizontal  cv2 waitKey 0      Methode 3  Using OpenCV  vconcat  hconcat  Fusion Vertical     cv2 vconcat  resizedLena  X  Y   Fusion Horizontal   cv2 hconcat  resizedLena  X  Y    cv2 imshow  quot Fusion Horizontal Using hconcat quot   Fusion Horizontal  cv2 waitKey 0

User · Answer

import numpy as np  cv2  img1   cv2 imread fn1  0  img2   cv2 imread fn2  0  h1  w1   img1 shape  2  h2  w2   img2 shape  2  vis   np zeros  max h1  h2   w1 w2   np uint8  vis  h1   w1    img1 vis  h2  w1 w1 w2    img2 vis   cv2 cvtColor vis  cv2 COLOR GRAY2BGR   cv2 imshow  test   vis  cv2 waitKey     or if you prefer legacy way   import numpy as np  cv  img1   cv LoadImage fn1  0  img2   cv LoadImage fn2  0   h1  w1   img1 height img1 width h2  w2   img2 height img2 width vis   np zeros  max h1  h2   w1 w2   np uint8  vis  h1   w1    cv GetMat img1  vis  h2  w1 w1 w2    cv GetMat img2  vis2   cv CreateMat vis shape 0   vis shape 1   cv CV 8UC3  cv CvtColor cv fromarray vis   vis2  cv CV GRAY2BGR   cv ShowImage  test   vis2  cv WaitKey

User · Answer

in OpenCV 3 0 you can use it easily as follow    combine 2 images same as to concatenate images with two different sizes h1  w1   img1 shape  2  h2  w2   img2 shape  2   create empty martrix  Mat  res   np zeros shape  max h1  h2   w1   w2  3   dtype np uint8    assign BGR values to concatenate images for i in range res shape 2          assign img1 colors     res  h1   w1  i    np ones  img1 shape 0   img1 shape 1      img1       i        assign img2 colors     res  h2  w1 w1   w2  i    np ones  img2 shape 0   img2 shape 1      img2       i   output img   res astype  uint8

[python] Combining Two Images with OpenCV

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