How to make all images in a folder the same pre-determined size

Hey I need to make 120 images the same size (800 pix (width) by 600 pix (height)). The pictures differ in ratio, so instead of stretching/skewing them, I'd like to cut equal amounts from the outer edge.

Is there a way of doing this in matlab (i.e. first compressing images to width of 800, then chopping height to 600)?

Thanks,

Isabel

[Shivaputra Narke]

Do you just want to resize the images?

[Walter Roberson]

If the images differ in aspect ratios then one of them might have a height less than 600 after the width has been adjusted to 800.

Answer 1

[Image Analyst]

See the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

Inside the loop, figure out the size reduction factor and call imresize, then get the new size and crop if necessary. Something like this (untested):

myFolder = 'C:\Documents and Settings\yourUserName\My Documents\My Pictures';
if ~isdir(myFolder)
  errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
  uiwait(warndlg(errorMessage));
  return;
end
filePattern = fullfile(myFolder, '*.jpg');
jpegFiles = dir(filePattern);
for k = 1:length(jpegFiles)
  baseFileName = jpegFiles(k).name;
  fullFileName = fullfile(myFolder, baseFileName);
  fprintf(1, 'Now reading %s\n', fullFileName);
  imageArray = imread(fullFileName);
  imshow(imageArray);  % Display image.
  drawnow; % Force display to update immediately.
  % Get initial size
  [rows, columns, numberOfColorChannels] = size(imageArray);
  % Get size reduction / magnification factor
  sizeFactor = 800 / columns;
  % Resize
  newImage = imresize(imageArray, sizeFactor);
  % Get the new size.
  [rows, columns, numberOfColorChannels] = size(imageArray);
  % Crop if necessary
  if rows > 600
    % Take upper 600 lines.  You could take lower or middle 600 also.
    newImage = imcrop(imageArray, [1,1,columns, 600]);
    newFileName = strrep(fullFileName, '.jpg', '_resized.jpg');
    imwrite(newImage, newFileName );
  end
end

Answer 2

[Shivaputra Narke]

Hope this helps.....

contents=ls;
for i=1:length(contents)
try
   tempImage=imread(contents(i,:));
   tempImage=imresize(tempImage,[600,800]);
   extnposn=find(contents(i,:)=='.');
   extn=contents(i,extnposn+1:end);
   extn(extn==' ')=[];
   name=contents(i,:);
   name(name==' ')=[];
   imwrite(tempImage,name,extn)
catch
    %write err msg as
    %use msgbox
end
end

[Walter Roberson]

That code changes the aspect ratio.

Answer 3

[Walter Roberson]

[rows, cols, panes] = size(tempImage);
aspratio = rows ./ cols;

now if aspratio < 3/4 then you need to resize so height becomes 600 and then chop width down to 800; otherwise you need to resize so width becomes 800 and then chop height down to 600.