Applying Quantization Matrix in which specific coefficients are zero'd out

Hello,

I'm trying to quantize 8x8 blocks using an 8x8 sample quantization matrix that I found online for image processing.

The only issue is that I want to be able to pick and choose which coefficients that I keep during quantization.

For instance if i want to zero out the circle'd portion of the matrix, how would I go about modifying my Quantization Matrix?

Sample Quantization Matrix and implementation:

Q_Matrix= [16 11 10 16 26 40 51 61

12 12 14 19 26 58 60 55

14 13 16 24 40 57 69 56

14 17 22 29 51 87 80 62

18 22 37 56 68 109 103 77

24 35 55 64 81 104 113 92

49 64 78 87 103 121 120 101

72 97 95 98 112 100 103 99];

Quantized_Matrix = floor(blocks_dct ./ Q_Matrix);

DeQuantized_Matrix = Quantized_Matrix .* Q_Matrix;

[Image Analyst]

You can't have matrices with "ragged" rows or columns, so what does "get rid of" mean to you? Do you mean to set their values to zero?

[KG573]

Yes, to set their values to zero.

Answer 1

[Matt J]

One way would be to set Q_matrix to twice the maximum of blocks_dct. That will ensure that the floor() operation zeros them.

Another way would be to apply a binary mask to zero_out the blocks_dct ellements appropriately,

Quantized_Matrix = floor(  (blocks_dct.*Mask) ./ Q_Matrix);