MATLAB: Black image after imread

imread image png

hello using this code:

I1 = imread('E:\Dropbox\Andrea VMS\Esame_di_Stato\Programmi\Spur_Gear\Spur11.PNG');
imshow(I1);
Y_j=input('Insert the geometrical coefficient of flexural resistance: '); 
close

appears a black window. using other images i have no problem. this is an image i scanned from a book

Best Answer

Try

imshow(I1, []);
message = sprintf('Max Value = %f\nMin Value = %f\n', max(I1(:)), min(I1(:)))
uiwait(helpdlg(message));

Also, check the values of I1 in the variable editor to see what they are.

Related Solutions

MATLAB: How can i automatically convert the input image to gray scale

Well it's a little bit tricky to detect the most common types of images: grayscale, RGB, and indexed . Of course your "binary image" is most likely a grayscale uint8 image with gray levels of only 0 and either 1 or 25. See this snippet which handles all of those, and adapt as needed:

%=====================================================================
% Reads FullImageFileName from disk into the axesImage axes.
function imageArray = DisplayImage(handles, fullImageFileName)
% Read in image.
imageArray = []; % Initialize
try
  [imageArray, colorMap] = imread(fullImageFileName);
  % colorMap will have something for an indexed image (gray scale image with a stored colormap).
  % colorMap will be empty for a true color RGB image or a monochrome gray scale image.
catch ME
  % Will get here if imread() fails, like if the file is not an image file but a text file or Excel workbook or something.
  errorMessage = sprintf('Error in program %s, function %s(), at line %d.\n\nError Message:\n%s', ...
    mfilename, ME.stack(1).name, ME.stack(1).line, ME.message);
  uiwait(warndlg(errorMessage));
  return;  % Skip the rest of this function
end
try
  % Display image array in a window on the user interface.
  %axes(handles.axesImage);
  hold off;  % IMPORTANT NOTE: hold needs to be off in order for the "fit" feature to work correctly.
  
  % Here we actually display the image in the "axesImage" axes.
  imshow(imageArray, 'InitialMagnification', 'fit', 'parent', handles.axesImage);
  
  % Display a title above the image.
  [folder, basefilename, extension] = fileparts(fullImageFileName);
  extension = lower(extension);
  % Display the title.
  caption = [basefilename, extension];
  title(handles.axesImage, caption, 'Interpreter', 'none', 'FontSize', 14);
  
  [rows, columns, numberOfColorChannels] = size(imageArray);
  % Get the file date
  fileInfo = dir(fullImageFileName);
  txtInfo = sprintf('%s\n\n%d lines (rows) vertically\n%d columns across\n%d color channels\n', ...
    [basefilename extension], rows, columns, numberOfColorChannels);
  % Tell user the type of image it is.
  if numberOfColorChannels == 3
    colorbar 'off';  % get rid of colorbar.

    txtInfo = sprintf('%s\nThis is a true color, RGB image.', txtInfo);
  elseif numberOfColorChannels == 1 && isempty(colorMap)
    colorbar 'off';  % get rid of colorbar.
    txtInfo = sprintf('%s\nThis is a gray scale image, with no stored color map.', txtInfo);
  elseif numberOfColorChannels == 1 && ~isempty(colorMap)
    txtInfo = sprintf('%s\nThis is an indexed image.  It has one "value" channel with a stored color map that is used to pseudocolor it.', txtInfo);
    colormap(colorMap);
    whos colorMap;
    %fprintf('About to apply the colormap...\n');
    % Thanks to Jeff Mather at the Mathworks to helping to get this working for an indexed image.
    colorbar('peer', handles.axesImage);
    %fprintf('Done applying the colormap.\n');
  end
catch ME
  errorMessage = sprintf('Error in program %s, function %s(), at line %d.\n\nError Message:\n%s', ...
    mfilename, ME.stack(1).name, ME.stack(1).line, ME.message);
  uiwait(warngld(errorMessage));
end
uiwait(helpdlg(txtInfo));
return; % from DisplayImage

MATLAB: How to convert gray or indexed images to color images

That image is a 2D image, an indexed image with a color map. It's not a 3D color RGB image. You need to convert it to an RGB image if you recognize it's an indexed image. Replace your loop with this:

for k = 1:numel(bmpFiles)
  fullInputFileName = fullfile(inputFolder,bmpFiles(k).name)
  [originalImage, colorMap] = imread(fullInputFileName);
  [rows, columns, numberOfColorChannels] = size(originalImage)
  if ~isempty(colorMap) && numberOfColorChannels == 1
    % It's an indexed image with a colormap.
    % Convert it to RGB color
    originalImage = ind2rgb(originalImage, colorMap);
    [rows, columns, numberOfColorChannels] = size(originalImage)
  end
  fullOutputFileName = fullfile(outputFolder, bmpFiles(k).name);
  outputImage = imresize(originalImage, [100,50]);
  [rows columns numberOfColorChannels] = size(outputImage);
  if numberOfColorChannels == 1
    % It's monochrome, so convert to color.
    outputImage = cat(3, outputImage, outputImage, outputImage);
  end
  
  figure,imshow(outputImage);
  imwrite(outputImage, fullOutputFileName);
end

Best Answer

Related Solutions

MATLAB: How can i automatically convert the input image to gray scale

MATLAB: How to convert gray or indexed images to color images

Related Question