17 lines
388 B
JavaScript
17 lines
388 B
JavaScript
|
'use strict';
|
||
|
|
|
||
|
|
module.exports = function paethPredictor(left, above, upLeft) {
|
||
|
|
|
||
|
|
var paeth = left + above - upLeft;
|
||
|
|
var pLeft = Math.abs(paeth - left);
|
||
|
|
var pAbove = Math.abs(paeth - above);
|
||
|
|
var pUpLeft = Math.abs(paeth - upLeft);
|
||
|
|
|
||
|
|
if (pLeft <= pAbove && pLeft <= pUpLeft) {
|
||
|
|
return left;
|
||
|
|
}
|
||
|
|
if (pAbove <= pUpLeft) {
|
||
|
|
return above;
|
||
|
|
}
|
||
|
|
return upLeft;
|
||
|
|
};
|