Hi, maybe the code below can help start you off! It's not a perfect segmentation, and I'm fairly new to MATLAB so someone else might have a better method. This link may also help you too, have a look under "Functions", then "Segmentation Techniques".
apple = imread("apple.jpg"); % read in image name
grayapple = rgb2gray(apple); % convert image to grayscale
level = graythresh(grayapple); % get threshold value
BWapple = imbinarize(grayapple,level); % binarize image using the threshold value
BWopen = bwpropfilt(~BWapple,"area",1,"largest"); % filter only the 1 largest blob. The ~ inverts the mask
BWfilled = imfill(BWopen,"holes"); % fill any missing holes
finalimage = imoverlay(apple,~BWfilled,"k"); % burn the mask onto the original image, with black (k) background
imshow(finalimage) % show the final image
