how can i find pixels of image's border

i have a set of images and i would like to test if there is a a black border on limits on the image, such this one:

i will appreciate any help ,thank you ^^

Answer 1

[harjeet singh]

you may use this code do set the th val according to the boarder noise

clear all
close all
clc

img=imread('images.jpg');
th=10;
a=img(:,:,1)>th & img(:,:,2)>th & img(:,:,3)>th;
a=bwareaopen(a,5000);
[r,c]=find(a==1);
b=img(min(r):max(r),min(c):max(c),:);

figure(1)
imshow(b)

Answer 2

[Image Analyst]

Your image has white columns on the left and right side - did you know that? So there are no all zero rows. To see if all pixels in a row or column are 0, use all():

allZeroColumns = all(grayImage == 0, 1);
allZeroRows = all(grayImage == 0, 2);

These are logical vectors. If you want, you can then use them to remove all zero rows or columns:

grayImage(:, allZeroColumns) = [];
grayImage(allZeroRows, :) = [];