% Scans data points from an image file
%
A=imread(input('Image file ','s'));
colormap('colorcube')
image(A)
%
fprintf('Click on the lower left, and then upper right corners of the plot\n');
[x,y]=ginput(2);
%
xvlo=input('X value at lower left corner ');
yvlo=input('Y value at lower left corner ');
xvhi=input('X value at upper right corner ');
yvhi=input('Y value at upper right corner ');
%
ax=(xvhi-xvlo)/(x(2)-x(1));
bx=xvlo-ax*x(1);
ay=(yvhi-yvlo)/(y(2)-y(1));
by=yvlo-ay*y(1);
%
fprintf('Now click on a point whose value you know\n');
test=ginput(1);
tx=ax*test(1)+bx;
ty=ay*test(2)+by;
fprintf('The coordinates of the point are (X,Y)=(%g,%g)\n',tx,ty);
%
fprintf('Now click on the data points.  <CR> when you are done.\n')
[x,y]=ginput;
xdata=ax*x+bx;
ydata=ay*y+by;
plot(xdata,ydata,'o')