Preprocessing satellite images to find crowns of trees using MATLAB

MATLAB Program: 
clear all;
close all;
g=imread('test_area_1.tif');
l=[100/255 75/255 50/255];
h=[255/255 255/255 250/255];
b=imadjust(g,[l;h],[0;1]);
H = padarray(2,[2 2]) - fspecial('gaussian' ,[5 5],2); % create unsharp mask
d=imfilter(b,H);
subplot(131);imshow(g);title('

original');
subplot(132);imshow(b);title('Contrast stretched image');
subplot(133);imshow(d);title('sharpened image');

By contrast stretching the image using imadjust and by applying high pass filter for sharpening, the results are as shown below: