storing image information in a 2-d array

2011 12 28
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hello everyone... my problem is i want to divide an color image into 100 blocks of equal size and then store the maximum color information present in the box in a 2d array of 10*10..for instance if the maximum color present in the block is black,it should store 0 in the corresponding cell of 2d array,if white then 1,if red then 2 and so on...i have finite number of colors in my image...i read an article on blockproc but i was unable to implement it...may i have some help or suggestions plz.... thnx in advance...any help is highly appreciated..:)

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Walter Roberson
Walter Roberson 2011-12-28
RGB images? Or pseudocolor but the color indices do not match your target numbers? Or pseudocolors and the color indices do already match your target numbers?
geekotronics
geekotronics 2011-12-29
yeah it would be rgb images....i would be setting the target numbers as per my need...i guess this can be done using a simple if-else condition...

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Chandra Kurniawan
Chandra Kurniawan 2011-12-28

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Hello,
That's true. You can use blockproc from Matlab.
It's simple to use.
B = blockproc(A,[M N],fun)
A is input image, [M N] is size of block, and fun is function handle
If you want to divide image into 100 equal block, then
you can divide image width and height by 10. This is for size of the block.
Here my sample code :
I = imread('peppers.png');
I = I(1:300,1:500,:);
[m n o] = size(I);
r = m/10;
c = n/10;
fun = @(block_struct) max(block_struct.data(:));
J = blockproc(I,[r c],fun)
J will returns 10x10 array that represent maximum value of each corresponding block.
J =
75 78 77 84 84 82 80 87 82 73
77 83 79 82 83 83 84 135 81 75
77 83 84 90 254 174 157 250 119 74
82 150 215 207 255 255 212 249 194 165
77 136 247 191 225 239 170 255 255 255
76 169 190 255 255 255 255 255 255 251
255 255 245 255 255 255 255 255 250 233
255 255 255 255 255 255 255 216 255 255
255 255 255 255 255 255 255 255 255 255
255 255 255 254 202 197 173 177 255 255
I hope this will helps you.

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geekotronics
geekotronics 2011-12-29
thnx a lot chandra...but can i define my own function instead of fun??i mean some function which is not been pre defined????
and do you know an alternative for bwdistgeodesic function...actually i want to find the shortest path between two objects in a image subjected to constraint...ie the path between the two objects should not cover up a particular color....my algorithm is i divided the image into various blocks and stored the color information in an array..now i want to trace a shortest path between two objects such that the path should cover up only a particular color....or the path should not cover a particular color....
Walter Roberson
Walter Roberson 2011-12-29
The line
fun = @(block_struct) max(block_struct.data(:));
defines fun right there, so it was not pre-defined.
geekotronics
geekotronics 2011-12-29
yeah it was...but i didnt mean the same....i meant that instead of max(block_struct.data(:)) ;,can i define it in some other way....like i thought of assigning 2 if the color is red,1 if it is white ,3 if it is blue and so on....i will be losing the color if i use max(block_struct.data(:))....

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