finding the gradient from image pixels..

Question

i have problem in calculating and finding gradients of pixels
int gradient1 = (y1 - y5) / (x1 - x5);  int gradient2 = (y2 - y5) / (x2 - x5);
from the image shown and the gradients calculations.. supposedly gradient1 = +ve value and gradient2 = -ve value..
but from the result i get both gradients are "0" i don't know where i have it wrong here.. if anyone could help me point out the mistake i've made.. thank you..

Frogleg · Accepted Answer

This is how I see it
int gradient1 = (y5 - y1)/(x5 - x1);
int gradient2 = (y5 - y2)/(x2 -  x5);
Are you tring to detect a smile ?
If so, you only need to know if y5 is a greater distance from the top (zero) than both y1 and y2

hanna banana · Answer

wow! that's true.. how can i not think of that :O thank you soo much!!