The Maths behind gesture: 'facing center'

[YaraAmin]

Can you explain to me the logic and the maths behind facing centre gesture in this code :

`for (let i = 0; i < res.length; i++) {
if (!res[i].annotations || !res[i].annotations.leftEyeIris || !res[i].annotations.rightEyeIris) continue;
const sizeXLeft = res[i].annotations.leftEyeIris[3][0] - res[i].annotations.leftEyeIris[1][0];
const sizeYLeft = res[i].annotations.leftEyeIris[4][1] - res[i].annotations.leftEyeIris[2][1];
const areaLeft = Math.abs(sizeXLeft * sizeYLeft);

const sizeXRight = res[i].annotations.rightEyeIris[3][0] - res[i].annotations.rightEyeIris[1][0];
const sizeYRight = res[i].annotations.rightEyeIris[4][1] - res[i].annotations.rightEyeIris[2][1];
const areaRight = Math.abs(sizeXRight * sizeYRight);

let center = false;
const difference = Math.abs(areaLeft - areaRight) / Math.max(areaLeft, areaRight);
if (difference < 0.25) {
  center = true;
  gestures.push({ iris: i, gesture: 'facing center' });
}`

Thank you

[vladmandic]

i'd consider actual value of iris: facing center gesture less important than similar one face: facing center which looks at the Z coordinates of corners of the eyes (not corners of the face as with higher angles face corner is likely not visible to start with)

iris: facing center is weird, but i've tried different methods and this algorithm gave ok results on average
it first calculates square area of each eye (areaLeft and areaRight) based on corners of the eye
and then if difference in eye areas is less than 25% it states facing center - meaning both eyes are of similar size so thus face is not turned to either side

you can think of iris: facing center as an intermediate result towards iris: looking center
method that states iris: looking center starts if iris: facing center is detected and then looks at difference between iris center and up/down/left/right corners of eyes and if iris is still in center, it states iris: looking center