You can get the coordinates from the bounding boxes:
row1 = boundingBox(2);
row2 = row1 + boundingBox(4);
col1 = boundingBox(1);
col2 = col1 + boundingBox(3);
subImage = yourImage(row1:row, col1:col2, :);
imwrite(subImage, filename);
or simply use imcrop():
subImage = imcrop(yourImage, boundingBox);
imwrite(subImage, filename);
