storing image information in a 2-d array

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..:)

[Walter Roberson]

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]

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...

Answer 1

[Chandra Kurniawan]

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.

[geekotronics]

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]

The line

fun = @(block_struct) max(block_struct.data(:));

defines fun right there, so it was not pre-defined.

[geekotronics]

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(:))....