Normalize image based on length of a line

I'm trying to normalize an image of a face based on the length between the top of the left ear and the inner point of the left eye. I use points collected from ginput(2) to create a line between the aforementioned points. But now I'm unsure of how to resize the full image to give the line specific dimensions.

I = imread(imgetfile);

%normalise: ear to inner eye point
image(I),title('Click on top of inner ear then inner eye')
[x,y] = ginput(2);

X1 = ceil(x(1,1)); Y1 = ceil(y(1,1));
X2 = floor(x(2,1)); Y2 = floor(y(2,1));

line = [X1:X2,Y1:Y2];

Answer 1

[Image Analyst]

You know the length of the line you drew

lineLength = sqrt((x(1)-x(2))^2 + (y(1)-y(2)^2);

and you know the desired line length, in pixels. So just compute the ratio and pass in to imresize

scaledImage = imresize(originalImage, desiredLength/lineLength);

[Ryan Snowden]

Thanks a ton