MATLAB: Error while using rgb2gray

imageimage analysisimage processingMATLAB

I m trying to accept series of color images and apply edge function on them. this is my code….

if true
for k = 1:10
   tifFilename = strcat( num2str(k), '.tif');
   [X,map] = imread(tifFilename);
   gmap = rgb2gray(map);
   BW = edge(gmap,'sobel');
   figure, imshow(BW);
end
end

it shows the following error

??? Error using ==> rgb2gray>parse_inputs at 82 MAP must be a m x 3 array.

Error in ==> rgb2gray at 35 X = parse_inputs(varargin{:});

Error in ==> sequenceimageprocessing at 6 gmap = rgb2gray(map);

Best Answer

Color images don't have a colormap. Try this

fontSize = 20;
for k = 1:10
   tifFilename = sprintf('%d.tif', k);
   if ~exist(tifFilename, 'file')
      fprintf('%s not found.\n', tifFilename);
      continue;
   end
   rgbImage = imread(tifFilename);
   grayImage = rgb2gray(rgbImage );
   BW = edge(grayImage ,'sobel');
   subplot(2,2,1);
   imshow(rgbImage);
   title('Color Image', 'FontSize', fontSize);
   subplot(2,2,2);
   imshow(grayImage );
   title('Grayscale Image', 'FontSize', fontSize);
   subplot(2,2,3);
   imshow(BW);
   title('Binary Edge Image', 'FontSize', fontSize);
end

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MATLAB: Crop dark area and display the face only

Convert to grayscale and then threshold and find the bounding box

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
% Read in the color image.
folder = pwd;
baseFileName = 'm2.bmp';
% 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
rgbImage = imread(fullFileName);
% Get the dimensions of the image.  numberOfColorBands should be = 3.
[rows, columns, numberOfColorBands] = size(rgbImage);
% Display the original color image.
subplot(2, 3, 1);
imshow(rgbImage, []);
axis on;
title('Original Color Image', 'FontSize', fontSize);
drawnow;
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Histogram the red channel, but there is a huge spike at 255 so let's not count those.
subplot(2, 3, 2);
grayImage = rgb2gray(rgbImage);
imshow(grayImage, []);
title('Gray Scale version', 'FontSize', fontSize);
subplot(2, 3, 3);
histogram(grayImage(grayImage<255))
grid on;
title('Histogram of Gray Scale Image', 'FontSize', fontSize);
someThresholdValue = 150;
binaryImage = grayImage > someThresholdValue;
% Take largest blob
binaryImage = bwareafilt(binaryImage, 1);
subplot(2, 3, 4);
imshow(binaryImage);
grid on;
title('Binary Image', 'FontSize', fontSize);
% Label the binary image.
labeledImage = bwlabel(binaryImage);
props = regionprops(labeledImage, 'BoundingBox');
bbox = props.BoundingBox
croppedImageRGB = imcrop(rgbImage, bbox);
subplot(2, 3, 5);
imshow(croppedImageRGB);
grid on;
title('Cropped RGB Image', 'FontSize', fontSize);
% Gray scale version of cropped image
croppedImageGray = imcrop(grayImage, bbox);
subplot(2, 3, 6);
imshow(croppedImageGray);
grid on;
title('Cropped Gray Scale Image', 'FontSize', fontSize);

MATLAB: Finding problem in retrieving output images from a function

Have the first line be

function i = MyFilter(A)

I advise you to use other names for the variables you call "i" and "filter" since they have special built-in meanings for MATLAB and you shouldn't overwrite them with your variables.

Best Answer

Related Solutions

MATLAB: Crop dark area and display the face only

MATLAB: Finding problem in retrieving output images from a function

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