# fingerprint image local orientation field extraction

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#### sambezi

##### Newbie level 4
I am extracting local orientation field of a grayscale fingerprint image using Rao's algorithm. I need urgent help to the correction of this error message that appears each time I run the code.
The error message is:

Index exceeds matrix dimensions.
Error in fp_local_orientation (line 21)
m.i.j=image(ii+3), jj+3)); % create sub image (such regions) of size...

Here is the code

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function img_orient = fp_local_orientation(image)
% image is passed to this function as argument
image(:,209:210)=255;

rows_image=size(image,1);
cols_image=size(image,2);

a=[];
for i = 1:4:rows_image % step in 5 down the image rows

b=[];
for j= 1:4:cols_image % step in 32 over the image columns

m.i.j=image(i:(i+3), j:(j+3)); % create sub images (sub regions) of size...

Gx = edge(m.i.j, 'sobel', 0.1112, 'horizontal');
Gy = edge(m.i.j, 'sobel', 0.0677, 'vertical');
angleT = 0.5 * atan((2*Gx.*Gy)./((Gx.^2) - (Gy.^2)));
angleT = angleT + pi/2;

b=[b angleT];
end
a=[a; b];
end
img_orient=a;

Last edited by a moderator:

#### andre_teprom

##### Super Moderator
Staff member
This code was really written in MATLAB ?

I had never seen such a ternary operation with the matrix operator "." especially getting the result of another operation, as well did not see any mention to a previous charge of value in the variable "m" at the code above.

#### sambezi

##### Newbie level 4
OK, thanks. Could that possibly be the error with the code?

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