phrogz / context-blender Goto Github PK

/**
 * JavaScript implementation of common blending modes, based on
 * http://stackoverflow.com/questions/5919663/how-does-photoshop-blend-two-images-together
 *
 * Note that I'm not using <code>this</code> to reference current object
 * for faster execution
 */
var blendingModes = {
    normal: function(a, b) {
        return a;
    },

    lighten: function(a, b) {
        return (b > a) ? b : a;
    },

    darken: function(a, b) {
        return (b > a) ? a : b;
    },

    multiply: function(a, b) {
        return (a * b) / 255;
    },

    average: function(a, b) {
        return (a + b) / 2;
    },

    add: function(a, b) {
        return Math.min(255, a + b);
    },

    substract: function(a, b) {
        return (a + b < 255) ? 0 : a + b - 255;
    },

    difference: function(a, b) {
        return Math.abs(a - b);
    },

    negation: function(a, b) {
        return 255 - Math.abs(255 - a - b);
    },

    screen: function(a, b) {
        return 255 - (((255 - a) * (255 - b)) >> 8);
    },

    exclusion: function(a, b) {
        return a + b - 2 * a * b / 255;
    },

    overlay: function(a, b) {
        return b < 128
            ? (2 * a * b / 255)
            : (255 - 2 * (255 - a) * (255 - b) / 255);
    },

    softLight: function(a, b) {
        return b < 128
            ? (2 * ((a >> 1) + 64)) * (b / 255)
            : 255 - (2 * (255 - (( a >> 1) + 64)) * (255 - b) / 255);
    },

    hardLight: function(a, b) {
        return blendingModes.overlay(b, a);
    },

    colorDodge: function(a, b) {
        return b == 255 ? b : Math.min(255, ((a << 8 ) / (255 - b)));
    },

    colorBurn: function(a, b) {
        return b == 0 ? b : Math.max(0, (255 - ((255 - a) << 8 ) / b));
    },

    linearDodge: function(a, b) {
        return blendingModes.add(a, b);
    },

    linearBurn: function(a, b) {
        return blendingModes.substract(a, b);
    },

    linearLight: function(a, b) {
        return b < 128
            ? blendingModes.linearBurn(a, 2 * b)
            : blendingModes.linearDodge(a, (2 * (b - 128)));
    },

    vividLight: function(a, b) {
        return b < 128
            ? blendingModes.colorBurn(a, 2 * b)
            : blendingModes.colorDodge(a, (2 * (b - 128)));
    },

    pinLight: function(a, b) {
        return b < 128
            ? blendingModes.darken(a, 2 * b)
            : blendingModes.lighten(a, (2 * (b - 128)));
    },

    hardMix: function(a, b) {
        return blendingModes.vividLight(a, b) < 128 ? 0 : 255;
    },

    reflect: function(a, b) {
        return b == 255 ? b : Math.min(255, (a * a / (255 - b)));
    },

    glow: function(a, b) {
        return blendingModes.reflect(b, a);
    },

    phoenix: function(a, b) {
        return Math.min(a, b) - Math.max(a, b) + 255;
    }
};