How can i conver this code to do the same thing fo white background ?

Remember to change directory of the picture.

    clc;
close all;
workspace;
format longg;
format compact;
fontSize = 20;
% Read in a standard MATLAB gray scale demo image.
folder = 'C:\Users\Monsterman\Documents';
baseFileName = 'test.jpg';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);

 end
grayImage = imread(fullFileName);
% Get the dimensions of the image.  
% numberOfColorBands should be = 1.
[rows columns numberOfColorBands] = size(grayImage)
% Display the original gray scale image.
subplot(2, 2, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Give a name to the title bar.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off') 
% Get all rows and columns where the image is nonzero
[nonZeroRows nonZeroColumns] = find(grayImage);
% Get the cropping parameters
topRow = min(nonZeroRows(:));
bottomRow = max(nonZeroRows(:));
leftColumn = min(nonZeroColumns(:));
rightColumn = max(nonZeroColumns(:));
% Extract a cropped image from the original.
croppedImage = grayImage(topRow:bottomRow, leftColumn:rightColumn);
% Display the original gray scale image.
subplot(2, 2, 2);
imshow(croppedImage, []);
title('Cropped Grayscale Image', 'FontSize', fontSize);

[Image Analyst]

You forgot to attach test.jpg so we cannot run this code yet with your image. Use the paper clip or image toolbar button.

Answer 1

[Image Analyst]

Try this:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures if you have the Image Processing Toolbox.
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 15;

% Read in a standard MATLAB color demo image.
folder = 'D:\Temporary stuff';
baseFileName = 'test.jpg';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
if ~exist(fullFileName, 'file')
  % Didn't find it there.  Check the search path for it.
  fullFileName = baseFileName; % No path this time.
  if ~exist(fullFileName, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
grayImage = imread(fullFileName);
% Get the dimensions of the image.  numberOfColorBands should be = 1.
[rows, columns, numberOfColorBands] = size(grayImage);
% Display the original image.
subplot(2, 2, 1);
imshow(grayImage);
axis on;
title('Original Gray Scale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);

% Find the mask
mask = ~(grayImage == 255);
% Get rid of small junk.
mask = bwareaopen(mask, 2500);
% Display the image.
subplot(2, 2, 2);
imshow(mask);
axis on;
title('Mask Image', 'FontSize', fontSize);
% Call regionprops to get the Bounding Box.
measurements = regionprops(mask, 'BoundingBox');

% Crop out the masked part
thisBoundingBox = measurements(1).BoundingBox
croppedImage = imcrop(grayImage, thisBoundingBox);
% Display the image.
subplot(2, 2, 3);
imshow(croppedImage);
axis on;
title('Cropped Image', 'FontSize', fontSize);

% Make another version with the background black
smallMask = croppedImage >= 251;
croppedImage2 = croppedImage; % Initialize.
croppedImage2(smallMask) = 0;
% Display the image.
subplot(2, 2, 4);
imshow(croppedImage2);
axis on;
title('Cropped Image', 'FontSize', fontSize);

msgbox('Results would be better if you use a PNG image instead of a JPG image.');

[Joakim]

Thank you! I can now make it work, you have been an excellent help!

cheers

Answer 2

[Image Analyst]

Try

[nonZeroRows, nonZeroColumns] = find(grayImage > 255); % Or whatever intensity the border is.

[Joakim]

The border is black, but when i try with

[nonZeroRows, nonZeroColumns] = find(grayImage > 255);

There is no crop (I have attached the picture)

[Image Analyst]

try

grayImage(grayImage >= 250) = 0;

[Joakim]

This helps, execpt the backgound is now black.

What im trying to get is a method of detecting a border, where the white/black background ends and crop it a few pixels off. This code works exceptional on the black background but i can't seem to figure out the problem with the wite back ground. Should i try a different method?

Thank you so much for taking the time to help a newcomer :)

[Image Analyst]

What exactly do you want? Do you want a much smaller picture where you have only the bounding box of the part? And no big surround of any color?

[Joakim]

Yes :) both. Lets say the picture have One color background(white/black/blue ect.). I want a way to find the edges of the motive inside the picture, and make a small margin to the new edge(cut a big picture to a smaller).( i hope this make a bit of sense, English is not my native language)