How can I find the square footage of an irregular driveway?
Approximately 9,800 square feet, assuming your drawing is accurate. I hastily colored in the image using MS Paint (not perfect, since JPG compression added a bunch of fuzzy grayscale values).

Then using MATLAB with the image processing toolbox:

width = 235; % establish scale parameters
height = 300;
img = imread('areatest.jpg'); % read image in 
bwImg = im2bw(img,0.5); % convert from JPG to binary BW
% find black pixels, divide by total image area, 
% and scale to square footage depicted in drawing:    
dwArea = sum(sum(~bwImg))/numel(bwImg)*width*height; 


You may be able to work this online, with the compile online website. However, I'm not sure if it can read in files from your hard drive.