I recently came across a technique called bit-plane slicing for image compression in a book "Digital image processing" by gonzalez and woods . They just presented the theory and i wanted to implement it . So ,my code just creates images out of 8th bit and 7th bit plane seperately and saves them . I just wanted to make sure that the output is really correct . please check these code and make it more efficient or give your own version.

import numpy as np
import cv2

#create a image array
img = cv2.imread("WIN_20170511_13_06_18_Pro.jpg",cv2.IMREAD_GRAYSCALE)
row ,col = img.shape
#convert each interger pixel value of given image to a bit pixel value of 8-
def intToBitArray(img) :
    list = []

    for i in range(row):
        for j in range(col):
             list.append (np.binary_repr( img[i][j] ,width=8  ) )

    return list #the binary_repr() fucntion returns binary values but in 
                #, not integer, which has it's own perk as you will notice   

 #as variable name says ,it's list of pixel values in binary , but in 1 
imgIn1D = intToBitArray(img)
#reshaping above 1D array to a matrix aka image
imgIn2D = np.reshape(imgIn1D , (360,640) )
def bitplane(bitImgVal , img1D ):

this function extracts the specific bit out of each binary pixel values of 
the matrix
for example , if bitImgVal = 3 , then , third bit of each pixel is extracted

:param bitImgVal: specifies the position of bit to be extracted
:param img1D: image which is to be compressed
:return: now returns 1 dimensional list of bits
    bitList = [  int(   i[bitImgVal]  )    for i in img1D]

    return bitList
#i don't know why but the multiplication factor is : 2^(n-1) where n is the 
bit number
#example, if binary pixel value is 11001010 and n = 3 , factor = 2^(3-1)
#image represented by 8th bit plane
eightbitimg = np.array( bitplane(0, imgIn1D ) ) * 128

#image represented by 7th bit plane
sevenbitimg = np.array( bitplane(1,imgIn1D) ) * 64

#bitplane of 8th and 7th bit
combine = eightbitimg + sevenbitimg
comb = np.reshape(combine,(row,col))

#save combined plane image

#save eight bit plane
eightbitimg = np.reshape(eightbitimg,(row,col))
cv2.imwrite("8bitvalue.jpg" , eightbitimg )

#save eight bit plane
sevenbitimg = np.reshape(sevenbitimg,(row,col))

#grayscale version of original image
gray = cv2.imread("WIN_20170511_13_06_18_Pro.jpg",cv2.IMREAD_GRAYSCALE)

the images are as : eigth BIt image:

enter image description here

seventh bit image

enter image description here


How about:

import cv2 
import numpy as np

img = cv2.imread('inputs/Lenna-220px.png', 0) 

out = []

for k in range(0, 7):
    # create an image for each k bit plane
    plane = np.full((img.shape[0], img.shape[1]), 2 ** k, np.uint8)
    # execute bitwise and operation
    res = cv2.bitwise_and(plane, img)
    # multiply ones (bit plane sliced) with 255 just for better visualization
    x = res * 255
    # append to the output list

cv2.imshow("bit plane", np.hstack(out))
| improve this answer | |

When we talk about Bit-Plane Slicing, we means to get each bit-plane eg. 0, 1 or more and then convert it to int and then try to show that bit plane. Then we will be able to see the impact of each Bit-Plane in image. My code do this as follow:

def getPlane(planeId, binary_image):
    switcher = {
        7:[int(b[0] + '0'*7) for b in binary_image],
        6:[int( '0' + b[1] + '0'*6) for b in binary_image],
        5:[int( '0'*2 + b[2] + '0'*5) for b in binary_image],
        4:[int( '0'*3 + b[3] + '0'*4) for b in binary_image],
        3:[int( '0'*4 + b[4] + '0'*3) for b in binary_image],
        2:[int( '0'*5 + b[5] + '0'*2) for b in binary_image],
        1:[int( '0'*6 + b[6] + '0') for b in binary_image],
        0:[int( '0'*7 + b[7]) for b in binary_image]
    return switcher.get(planeId, None)

# image size is (225, 225)
bit_planes = []
c = 0
while( c < 225*225):
    bit_planes.append (np.binary_repr( img[c][0] ,width=8  ) )
    c  = c + 1
c = 0
while(c < 8):
    cv.imwrite('Bit_Plane\plane'+str(c)+ '.jpg', np.array(getPlane(c, bit_planes)).reshape(225, 225))
    c = c + 1

5th Bit-Plane7th Bit-Plane

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.