OpenCV Python rotate image by X degrees around specific point

Question

I m having a hard time finding examples for rotating an image around a specific point by a specific  often very small  angle in Python using OpenCV   This is what I have so far  but it produces a very strange resulting image  but it is rotated somewhat   def rotateImage  image  angle        if image    None          dst image   cv CloneImage  image            rotate around    0 0          transl   cv CreateMat 2  3  cv CV 32FC1            matrix   cv GetRotationMatrix2D  rotate around  angle  1 0  transl           cv GetQuadrangleSubPix  image  dst image  transl           cv GetRectSubPix  dst image  image  rotate around        return dst image

User · Answer

Here s an example for rotating about an arbitrary point  x y  using only openCV def rotate about point x  y  degree  image       rot mtx   cv getRotationMatrix2D  x  y   angle  1      abs cos   abs rot mtx 0  0       abs sin   abs rot mtx 0  1       rot wdt   int frm hgt   abs sin   frm wdt   abs cos      rot hgt   int frm hgt   abs cos   frm wdt   abs sin      rot mtx    np asarray   0  0  -lftmost x                               0  0  -topmost y        rot img   cv warpAffine image  rot mtx   rot wdt  rot hgt                               borderMode cv BORDER CONSTANT      return rot img

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import imutils  vs   VideoStream src 0  start        while  1      frame   vs read              frame   imutils rotate frame  45    More  https   github com jrosebr1 imutils

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I had issues with some of the above solutions  with getting the correct  bounding box  or new size of the image  Therefore here is my version  def rotation image  angleInDegrees       h  w   image shape  2      img c    w   2  h   2       rot   cv2 getRotationMatrix2D img c  angleInDegrees  1       rad   math radians angleInDegrees      sin   math sin rad      cos   math cos rad      b w   int  h   abs sin      w   abs cos        b h   int  h   abs cos      w   abs sin         rot 0  2       b w   2  - img c 0       rot 1  2       b h   2  - img c 1        outImg   cv2 warpAffine image  rot   b w  b h   flags cv2 INTER LINEAR      return outImg

User · Answer

You can simply use the imutils package to do the  rotation  it has two methods    rotate  Rotate the image at specified angle  however the drawback is image might get cropped if it is not a square image  Rotate bound  it overcomes the problem happened with rotate  It adjusts the size of the image accordingly while rotating the image    more info you can get on this blog  https   www pyimagesearch com 2017 01 02 rotate-images-correctly-with-opencv-and-python

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import numpy as np import cv2  def rotate image image  angle     image center   tuple np array image shape 1  -1     2    rot mat   cv2 getRotationMatrix2D image center  angle  1 0    result   cv2 warpAffine image  rot mat  image shape 1  -1   flags cv2 INTER LINEAR    return result  Assuming you re using the cv2 version  that code finds the center of the image you want to rotate  calculates the transformation matrix and applies to the image

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The cv2 warpAffine function takes the shape parameter in reverse order   col row  which the answers above do not mention   Here is what worked for me    import numpy as np  def rotateImage image  angle       row col   image shape     center tuple np array  row col   2      rot mat   cv2 getRotationMatrix2D center angle 1 0      new image   cv2 warpAffine image  rot mat   col row       return new image

User · Answer

Quick tweak to  alex-rodrigues answer    deals with shape including the number of channels   import cv2 import numpy as np  def rotateImage image  angle       center tuple np array image shape 0 2   2      rot mat   cv2 getRotationMatrix2D center angle 1 0      return cv2 warpAffine image  rot mat  image shape 0 2  flags cv2 INTER LINEAR

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Or much easier use SciPy  from scipy import ndimage   rotation angle in degree rotated   ndimage rotate image to rotate  45    see here  for more usage info

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def rotate image  angle  center   None  scale   1 0        h  w    image shape  2       if center is None          center    w   2  h   2         Perform the rotation     M   cv2 getRotationMatrix2D center  angle  scale      rotated   cv2 warpAffine image  M   w  h        return rotated

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You can easily rotate the images using opencv python-  def funcRotate degree 0       degree   cv2 getTrackbarPos  degree   Frame       rotation matrix   cv2 getRotationMatrix2D  width   2  height   2   degree  1      rotated image   cv2 warpAffine original  rotation matrix   width  height       cv2 imshow  Rotate   rotated image    If you are thinking of creating a trackbar  then simply create a trackbar using cv2 createTrackbar   and the call the funcRotate  fucntion from your main script  Then you can easily rotate it to any degree you want  Full details about the implementation can be found here as well- Rotate images at any degree using Trackbars in opencv

[python] OpenCV Python rotate image by X degrees around specific point

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