html2canvas/src/gradientcontainer.js

function GradientContainer(imageData) {
    this.src = imageData.value;
    this.colorStops = [];
    this.type = null;
    this.x0 = 0.5;
    this.y0 = 0.5;
    this.x1 = 0.5;
    this.y1 = 0.5;
    this.promise = Promise.resolve(true);
}

GradientContainer.prototype.TYPES = {
    LINEAR: 1,
    RADIAL: 2
};