\frametitle {Matlab code to simulate a JPEG compression cycle (3)}
\begin{lstlisting}
  % Dequantize DCT coefficients
  y  = blockproc( y, [8 8], @(block_struct) block_struct.data .* q_y);
  cb = blockproc(cb, [8 8], @(block_struct) block_struct.data .* q_c);
  cr = blockproc(cr, [8 8], @(block_struct) block_struct.data .* q_c);

  % Inverse DCT
  y  = blockproc( y ./ q_max, [8 8], idct);
  cb = blockproc(cb ./ q_max, [8 8], idct);
  cr = blockproc(cr ./ q_max, [8 8], idct);

  % Up-sample chroma
  upsample_filter_1d = [1 3 3 1] / 4;
  upsample_filter = upsample_filter_1d' * upsample_filter_1d;
  cb = conv2(upsample_filter,
             upsample(upsample(padarray(cb, [1 1], 'replicate'), 2)', 2)');
  cb = cb(4 : size(cb, 1) - 4, 4 : size(cb, 2) - 4);
  cr = conv2(upsample_filter,
             upsample(upsample(padarray(cr, [1 1], 'replicate'), 2)', 2)');
  cr = cr(4 : size(cr, 1) - 4, 4 : size(cr, 2) - 4);

  % Concatenate the channels
  jpeg_result = ycbcr2rgb(cat(3, y, cb, cr));
end
\end{lstlisting}