r=imRGB(:，:， 1)；

g=imRGB(:，:，2)；

b=imRGB(:，:，3)； Respectively extracting three-color gray-scale images

[m n] = size (r); Extract the width and length of monochrome graphics matrix

A = zero (m, n); Create a zero matrix a of m * n.

Because i = 1: m

For j = 1: n

a(i，j) = min(r(i，j)，g(i，j))；

a(i，j)= min(a(i，j)，b(i，j))； The minimum values of the three color components are sequentially compared and extracted as a dark channel graph.

end

end

D = unit (15,15); Use 15* 15 to create identity matrix.

fun = @(block _ struct)min(min(block _ struct . data))* d；

dark = blockproc(a，[ 15 15]，fun)； Divide the picture into small blocks of 15* 15, and make each block take the minimum value.

Dark = dark (1:m,1:n);

I'm a novice, too, brother. I can only help you here.