How can the image be like this?

Hi, I'm a newbie and need help. I want my pictures to focus on vegetables. and the back is a black background that is the same size as the original image. Can you help me? how do writing code

thanks for the help really appreciate it

Answer 1

[DGM]

This is one way:

A = imread('peppers.png');
imshow(A)

B = zeros(size(A),class(A)); % black image
B(100:250,200:350,:) = A(100:250,200:350,:); % copy ROI from original image
imshow(B)

[mayy noensai]

omg thank you so much

Answer 2

[Image Analyst]

Use the Color Thresholder App on the Apps tab of the tool ribbon. See if this is what you really want:

% Demo by Image Analyst, April, 2022.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clearvars;
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 16;
fprintf('Beginning to run %s.m ...\n', mfilename);
%-----------------------------------------------------------------------------------------------------------------------------------
% Read in image.
folder = [];
baseFileName = 'food.jpeg';
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~isfile(fullFileName)
    % The file doesn't exist -- didn't find it there in that folder.
    % Check the entire search path (other folders) for the file by stripping off the folder.
    fullFileNameOnSearchPath = baseFileName; % No path this time.
    if ~exist(fullFileNameOnSearchPath, 'file')
        % Still didn't find it.  Alert user.
        errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
        uiwait(warndlg(errorMessage));
        return;
    end
    fullFileName = fullFileNameOnSearchPath;
end
rgbImage = imread(fullFileName);
[rows, columns, numberOfColorChannels] = size(rgbImage)
% Crop away other stuff in the screenshot to get the image along.
rgbImage = rgbImage(400:1800, 200:972,:);
% Display the image.
subplot(2, 2, 1);
imshow(rgbImage, []);
axis('on', 'image');
impixelinfo;
caption = sprintf('RGB Image : "%s"', baseFileName);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Set up figure properties:
% Enlarge figure to full screen.
hFig1 = gcf;
hFig1.Units = 'Normalized';
hFig1.WindowState = 'maximized';
% Get rid of tool bar and pulldown menus that are along top of figure.
% set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
hFig1.Name = 'Demo by Image Analyst';
%--------------------------------------------------------------------------------------------------------
% Segment (mask) the image.
[mask,maskedRGBImage] = createMask(rgbImage);
% Display the image.
subplot(2, 2, 2);
imshow(mask, []);
axis('on', 'image');
impixelinfo;
title('Initial Mask', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Need to fix the mask.
mask = imfill(mask, 'holes'); % Fill holes in blobs.
mask = bwareafilt(mask, 1); % Take largest blob.
% Display the image.
subplot(2, 2, 3);
imshow(mask, []);
axis('on', 'image');
impixelinfo;
title('Final Mask', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Construct new masked RGB image with new mask
% Mask the image using bsxfun() function to multiply the mask by each channel individually.  Works for gray scale as well as RGB Color images.
maskedRgbImage = bsxfun(@times, rgbImage, cast(mask, 'like', rgbImage));
% Display the image.
subplot(2, 2, 4);
imshow(maskedRgbImage, []);
axis('on', 'image');
impixelinfo;
title('Masked Image', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
%=======================================================================================================
% Color Thresholder generated code.
function [BW,maskedRGBImage] = createMask(RGB)
%createMask  Threshold RGB image using auto-generated code from colorThresholder app.
%  [BW,MASKEDRGBIMAGE] = createMask(RGB) thresholds image RGB using
%  auto-generated code from the colorThresholder app. The colorspace and
%  range for each channel of the colorspace were set within the app. The
%  segmentation mask is returned in BW, and a composite of the mask and
%  original RGB images is returned in maskedRGBImage.
% Auto-generated by colorThresholder app on 24-Apr-2022
%------------------------------------------------------
% Convert RGB image to chosen color space
I = rgb2hsv(RGB);
% Define thresholds for channel 1 based on histogram settings
channel1Min = 0.054;
channel1Max = 0.311;
% Define thresholds for channel 2 based on histogram settings
channel2Min = 0.390;
channel2Max = 1.000;
% Define thresholds for channel 3 based on histogram settings
channel3Min = 0.374;
channel3Max = 1.000;
% Create mask based on chosen histogram thresholds
sliderBW = (I(:,:,1) >= channel1Min ) & (I(:,:,1) <= channel1Max) & ...
    (I(:,:,2) >= channel2Min ) & (I(:,:,2) <= channel2Max) & ...
    (I(:,:,3) >= channel3Min ) & (I(:,:,3) <= channel3Max);
BW = sliderBW;
% Initialize output masked image based on input image.
maskedRGBImage = RGB;
% Set background pixels where BW is false to zero.
maskedRGBImage(repmat(~BW,[1 1 3])) = 0;
end