Digitally, an image is represented in terms of
pixels.

These pixels can be expressed further in terms of
bits.

Consider the image ‘coins.png’ and the pixel
representation of the image.

Consider the pixels that are bounded within the
yellow line. The binary formats for those values are (8-bit representation)

The binary format for the pixel value 167 is
10100111

Similarly, for 144 it is 10010000

This 8-bit image is composed of eight 1-bit planes.

Plane 1 contains the lowest order bit of all the
pixels in the image.

And plane 8 contains the highest order bit of all
the pixels in the image.

Let’s see how we can do this using MATLAB

A=[167 133 111

144 140 135

159 154 148]

B=bitget(A,1);
%Lowest order bit of all pixels

‘bitget’ is a MATLAB function used to fetch a bit from the specified position from all the
pixels.

B=[1 1 1

0 0 1

1 0 0]

B=bitget(A,8);%Highest order bit of all pixels

B=[1 1 0

1 1 1

1 1 1]

__MATLAB CODE:__**%Bit Planes from 1 to 8. Output Format: Binary**

A=imread('coins.png');

B=bitget(A,1);

figure,

subplot(2,2,1);imshow(logical(B));title('Bit
plane 1');

B=bitget(A,2);

subplot(2,2,2);imshow(logical(B));title('Bit
plane 2');

B=bitget(A,3);

subplot(2,2,3);imshow(logical(B));title('Bit
plane 3');

B=bitget(A,4);

subplot(2,2,4);imshow(logical(B));title('Bit
plane 4');

B=bitget(A,5);

figure,

subplot(2,2,1);imshow(logical(B));title('Bit
plane 5');

B=bitget(A,6);

subplot(2,2,2);imshow(logical(B));title('Bit
plane 6');

B=bitget(A,7);

subplot(2,2,3);imshow(logical(B));title('Bit
plane 7');

B=bitget(A,8);

subplot(2,2,4);imshow(logical(B));title('Bit
plane 8');

__Image reconstruction using n bit planes.__
1. The
nth plane in the pixels are multiplied by the constant 2^n-1

2. For
instance, consider the matrix

A= A=[167 133 111

144 140 135

159 154 148] and the
respective bit format

3. Combine
the 8 bit plane and 7 bit plane.

For 10100111, multiply the 8 bit
plane with 128 and 7 bit plane with 64.

(1x128)+(0x64)+(1x0)+(0x0)+(0x0)+(1x0)+(1x0)+(1x0)=128

4. Repeat
this process for all the values in the matrix and the final result will be

[128 128 64

128 128 128

128 128 128]

**MATLAB CODE:**
%Image reconstruction
by combining 8 bit plane and 7 bit plane

A=imread('coins.png');

B=zeros(size(A));

B=bitset(B,7,bitget(A,7));

B=bitset(B,8,bitget(A,8));

B=uint8(B);

figure,imshow(B);

Image reconstructed using 8 and 7 bit planes |

Explanation:

‘bitset’ is used to
set a bit at a specified position. Use ‘bitget’
to get the bit at the positions 7 and 8 from all the pixels in matrix A and use
‘bitset’ to set these bit values at the positions 7 and 8 in the matrix B.

%Image
reconstruction by combining 8,7,6 and 5 bit planes

A=imread('coins.png');

B=zeros(size(A));

B=bitset(B,8,bitget(A,8));

B=bitset(B,7,bitget(A,7));

B=bitset(B,6,bitget(A,6));

B=bitset(B,5,bitget(A,5));

B=uint8(B);

figure,imshow(B);

Image reconstructed using 5,6,7 and 8 bit planes |

Also check bit plane compression.