Convert red portion to white and the background to black . Second part is to detect road sign and put bounding box on it.

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renit anthony 2020-9-18

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https://ww2.mathworks.cn/matlabcentral/answers/595987-convert-red-portion-to-white-and-the-background-to-black-second-part-is-to-detect-road-sign-and-pu

评论： renit anthony 2020-9-18

采纳的回答： Image Analyst

I need to extract the road sign from an image. Can someone help me with this as I am new to matlab.

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Answer 1

Image Analyst 2020-9-18

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Try the Color Thresholder on the Apps tab of the tool ribbon. Otherwise look in the Computer Vision Toolbox or Automated Driving Toolbox for road sign demos.

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Image Analyst 2020-9-18

在 MATLAB Online 中打开

Looks like you didn't try my suggestion. If you had, you would have ended up with something like this:

% Demo to find road signs.  By Image Analyst, Sep 18, 2020.
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 = 'double.jpg';
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
	% 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
end
rgbImage = imread(fullFileName);
[rows, columns, numberOfColorChannels] = size(rgbImage)
% Display the test image.
subplot(2, 2, 1);
imshow(rgbImage, []);
axis('on', 'image');
caption = sprintf('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';
% Get red stuff
[mask, maskedRGBImage] = createMask(rgbImage);
% Display the initial mask image.
subplot(2, 2, 2);
imshow(mask, []);
axis('on', 'image');
title('Initial Color Segmentation Mask', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
% Fill holes
mask = imfill(mask, 'holes');
props = regionprops(mask, 'area');
allAreas = sort([props.Area], 'descend')
% Get rid of small blobs less than 1000 pixels in area.
mask = bwareaopen(mask, 1000);
% Display the final mask image.
subplot(2, 2, 3);
imshow(mask, []);
axis('on', 'image');
title('Final Road Sign Mask', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% 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 final mask image.
subplot(2, 2, 4);
imshow(maskedRgbImage, []);
axis('on', 'image');
title('Final Masked Red Road Sign', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
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 18-Sep-2020
%------------------------------------------------------
% Convert RGB image to chosen color space
I = rgb2hsv(RGB);
% Define thresholds for channel 1 based on histogram settings
channel1Min = 0.980;
channel1Max = 0.057;
% Define thresholds for channel 2 based on histogram settings
channel2Min = 0.210;
channel2Max = 1.000;
% Define thresholds for channel 3 based on histogram settings
channel3Min = 0.367;
channel3Max = 0.679;
% 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

Do the same for yellow but create a new masking function for yellow using the Color Thresholder.

Image Analyst 2020-9-18

testRGBImage.m

You need to find thresholds for "red" that work for the entire range of "reds" that you expect to see. I made some adjustments using the Color Thresholder and it works fine. Not sure why are not even trying that app, but you really should.