How to get dct of an image in python using opencv

dct, opencv, python

Solution

I found the solution. As I said we need to convert to float that too within range 0 to 1. Then we can convert it back after computing DCT:

imf = np.float32(imgcv1)/255.0  # float conversion/scale
dct = cv2.dct(imf)              # the dct
imgcv1 = np.uint8(dct*255.0)    # convert back to int

Problem

I've been trying to figure out a way of getting a DCT of image. After getting the image and doing a bunch of filtering, I want to calculate DCT. Following is the code sniplet: ``` imgcv1 = cv2.split(imgcv)[0] cv2.boxFilter(imgcv1, 0, (7,7), imgcv1, (-1,-1), False, cv2.BORDER_DEFAULT) #resize image to 32x32 cv2.resize( imgcv1, (32, 32 ) ,imgcv1) ``` I've been trying to play around with the description given here but no success. When I tried something like: ``` dst = cv2.dct(imgcv1) ``` I get an error like: ``` cv2.error: /build/buildd/opencv-2.3.1/modules/core/src/dxt.cpp:2247: error: (-215) type == CV_32FC1 || type == CV_64FC1 in function dct ``` From what I can understand from the error is that the input is not 32 bit float but 8 bit. How may I convert it and pass it as 32 bit float? I am not sure of the problem. I would be grateful for your help. How can I get the DCT? I am pretty new to openCV and python. I searched through other 2/3 threads on same topic but it did not work.

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