Hand Segmentation Based on Thresholding Coding \\ image processing

my project is about to segment the hand from the background, i try this code it works well with some image only ! but the image with complex background does not work correctly this is the code

   clc;
  workspace
  fontSize = 20;
  folder = '/Users/lolo/Desktop';
  baseFileName = 'A.png';
  % Get the full filename, with path prepended.
  fullFileName = fullfile('/Users/Roa/Desktop', 'A.png');
  currentimg=imread(fullFileName);
  %capture the image of interest%
  subplot(2,2,1);
  imshow(currentimg);
  title('Original Image', 'FontSize', fontSize);
  %Read the image, and capture the dimensions
  VidImage = currentimg;
  height = size(VidImage,1);
  width = size(VidImage,2);
  %Initialize the output images
  out = VidImage;
  bin = zeros(height,width);
  %Convert the image from RGB to YCbCr
  img_ycbcr = rgb2ycbcr(VidImage);
  Cb = img_ycbcr(:,:,2);
  Cr = img_ycbcr(:,:,3);
  %Detect Skin
  [r,c,v] = find(Cb>=77 & Cb<=127 & Cr>=133 & Cr<=173);
  numind = size(r,1);
  %Mark Skin Pixels
  for i=1:numind
      out(r(i),c(i),:) = [0 0 255];
      bin(r(i),c(i)) = 1;
  end
  binaryImage= imbinarize(bin,graythresh(bin));
  % binaryImage=~binaryImage;
  subplot(2,2,2);
  imshow(binaryImage);
  title('Binary Image', 'FontSize', fontSize);
  B = bwboundaries(binaryImage);
  % imshow(binaryImage)
  binaryImage = imfill(binaryImage, 'holes');
  % Remove tiny regions.
  binaryImage = bwareaopen(binaryImage, 5000);
  subplot(2,2,3);
  imshow(binaryImage);
  title('Second Binary Image', 'FontSize', fontSize);
  %---------------------------------------------------------------------------
  % Extract the largest area using ImageAnalyst's custom function ExtractNLargestBlobs().
  biggestBlob = ExtractNLargestBlobs(binaryImage, 1);
  % Display the image.
  subplot(2,2, 4);
  imshow(biggestBlob);
  title('Final Image', 'FontSize', fontSize);
  %--------------------------------------------------------------------------
  [labeledImage, numberOfBlobs] = bwlabel(biggestBlob, 8);
  % Get all the blob properties.
  blobMeasurements = regionprops(labeledImage, 'BoundingBox','Area');
  allBlobAreas = [blobMeasurements.Area];
  % Display the original gray scale image.
  subplot(2,2,1);
  % Loop through all blobs, putting up Bounding Box.
  hold on; % Prevent boxes from blowing away the image and prior boxes.
  for k = 1 : numberOfBlobs
        boundingBox = blobMeasurements(k).BoundingBox;   % Get box.
        x1 = boundingBox(1);
        y1 = boundingBox(2);
        x2 = x1 + boundingBox(3) - 1;
        y2 = y1 + boundingBox(4) - 1;
        verticesX = [x1 x2 x2 x1 x1];
        verticesY = [y1 y1 y2 y2 y1];
        plot(verticesX, verticesY, 'r-', 'LineWidth', 2);
  end
  uiwait(msgbox('Done with demo'));

[Guillaume]

Your question is essentially:

Here is some code. I'm not going to explain how it works and what it does, but can somebody spends the time to understand it, then improve it so that it works on some unspecified set of images that I'm not going to show.

Image processing of completely arbitrary images is very hard. If you don't restrict what is allowed in the image you're never going to have 100% working code.

[Image Analyst]

Really? I didn't even see a question there. It looks more like an announcement to me.