How to crop Top, Left, Bottom, and Right boundaries in an image?

Question

I'm trying to crop the top, left, bottom, and right boundaries of the image below.

So, basically, I'm looking to create something that would take the image above as the input and output these images:

The straight lines and their dimensions can be detected using houghlines in MATLAB, but how can I find the positions of the convex and concave pieces in the image? I tried using regionprops and the extrema property, but it would not detect the concave curves (only gave points for the extrema of the convex curves.) I need to find out the lowest/highest points in the concave/convex curves but I'm not sure how to go about that. I have the step after that figured out though; I can easily use imcrop to crop out the respective boundaries once I know them.

Answer 1

Code

%%// Tolerance in percentage for the outliers/noise in the image because 
%%// of which the edges are not perfectly vertical or horizontal and 
%%// the ovalish blobs are not "round" enough
f=2;

%%// Read in your image
img = im2bw(imread('patt1.png'));

%%// Main processing
sum1 = sum(img,1);
box_startx = find(sum1>0.33*size(img,1),1);
box_stopx = size(img,2) - find(fliplr(sum1)>0.33*size(img,1),1) + 1;

sum2 = sum(img,2)'; %'
box_starty = find(sum2>0.33*size(img,2),1);
box_stopy = size(img,1) - find(fliplr(sum2)>0.33*size(img,2),1) + 1;

blob_leftx = find(sum1>(1-0.01*f)*max(sum1),1);
blob_rightx = size(img,2) - find(fliplr(sum1)>(1-0.01*f)*max(sum1),1) + 1;

blob_topy = find(sum2>(1-0.01*f)*max(sum2),1);
blob_bottomy = size(img,1) - find(fliplr(sum2)>(1-0.01*f)*max(sum2),1) + 1;

top1 = img(1:blob_topy,box_startx+1:box_stopx);
left1 = img(box_starty:box_stopy-1,1:blob_leftx);
bottom1 = img(blob_bottomy:end,box_startx:box_stopx);
right1 = img(box_starty:box_stopy,blob_rightx:end);

%// Debug
figure,
subplot(2,2,1);imshow(top1)
subplot(2,2,2);imshow(bottom1)
subplot(2,2,3);imshow(left1)
subplot(2,2,4);imshow(right1)

Output