#!/usr/bin/env python
# coding: utf-8

# In[1]:


import cv2 as cv
import numpy as np


# In[2]:


img = cv.imread('reflections.jpg')


# In[9]:


def BGR2YCbCr(bgrimg):
    ycbcrimg = np.empty(bgrimg.shape, np.float32)
    for r in range(bgrimg.shape[0]):
        for c in range(bgrimg.shape[1]):
            #ycbcrimg[r,c,0] = bgrimg[r,c,0]*0.114 + bgrimg[r,c,1]*0.587 + bgimg[r,c,2]*0.299
            ycbcrimg[r,c,0] = sum(bgrimg[r,c]*np.array([0.114,0.587,0.299]))
            ycbcrimg[r,c,1] = 128 + sum(bgrimg[r,c] * np.array([0.5, -0.331264,-0.168736]))
            ycbcrimg[r,c,2] = 128 + sum(bgrimg[r,c] * np.array([-0.08132, -0.418688,0.5]))
    return ycbcrimg


# In[5]:


img.shape


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def YCbCr2BGR(ycbcrimg):
    bgrimg = np.empty(ycbcrimg.shape, np.uint8)
    for r in range(ycbcrimg.shape[0]):
        for c in range(ycbcrimg.shape[1]):
            # I have a row r and col c
            blue = ycbcrimg[r,c,0] + 1.772 * (ycbcrimg[r,c,1] - 128)
            if blue < 0:
                blue = 0
            elif blue > 255:
                blue = 255
            bgrimg[r,c,0] = blue
            
            green = ycbcrimg[r,c,0] - 0.344136 * (ycbcrimg[r,c,1] - 128) - \
                            0.714136 * (ycbcrimg[r,c,2] - 128)
            if green < 0:
                green = 0
            elif green > 255:
                green = 255
            bgrimg[r,c,1] = green
            
            red = ycbcrimg[r,c,0] + 1.402 * (ycbcrimg[r,c,2] - 128)
            if red < 0:
                red = 0
            elif red > 255:
                red = 255
            bgrimg[r,c,2] = red
            
    return bgrimg


# In[18]:


ycbcr_image = BGR2YCbCr(img)


# In[19]:


bgr_image = YCbCr2BGR(ycbcr_image)


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cv.imshow('original', img)
cv.imshow('converted back and forth', bgr_image)
cv.waitKey(0)
cv.destroyAllWindows()


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diffimg = img - bgr_image


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cv.imshow('should be black', diffimg)
cv.waitKey(0)
cv.destroyAllWindows()


# In[23]:


diffimg[0,0]


# In[24]:


yblurred = cv.GaussianBlur(ycbcr_image[:,:,0], [11,11], 4)


# In[25]:


yblurred.shape


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ycbcr_image[:,:,0] = yblurred


# In[27]:


blurred_image = YCbCr2BGR(ycbcr_image)


# In[28]:


cv.imshow('original', img)
cv.imshow('blurred', blurred_image)
cv.waitKey(0)
cv.destroyAllWindows()


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