OpenCV Straighten an Image with Python

Question

Is there any way that I can straighten this image using OpenCV with Python? I was figuring it out using the different transformations but I cant get it.

Here is my code:

rows, cols, h = img.shape

M = np.float32([[1, 0, 100], [0, 1, 50]])

And then I apply Affine Transformation.

dst = cv2.warpAffine(roi, M, (cols, rows))

Still I cant get the desired output of the image to be straighten. Scratching my head for almost an hour now. Anyone can help me please?

Answer 1

Do you remember my previous post? This answer is based on that.

So I obtained the 4 corner points of the bounding box around the book and fed it into the homography function.

Code:

#---- 4 corner points of the bounding box
pts_src = np.array([[17.0,0.0], [77.0,5.0], [0.0, 552.0],[53.0, 552.0]])

#---- 4 corner points of the black image you want to impose it on
pts_dst = np.array([[0.0,0.0],[77.0, 0.0],[ 0.0,552.0],[77.0, 552.0]])

#---- forming the black image of specific size
im_dst = np.zeros((552, 77, 3), np.uint8)

#---- Framing the homography matrix
h, status = cv2.findHomography(pts_src, pts_dst)

#---- transforming the image bound in the rectangle to straighten
im_out = cv2.warpPerspective(im, h, (im_dst.shape[1],im_dst.shape[0]))
cv2.imwrite("im_out.jpg", im_out)

Since you have the contour bounding box around the book; you have to feed those 4 points into the array pts_src.