_setRotations(tiledImage, useSketch = false) {
        var saveContext = false;
        if (this.viewport.getRotation(true) % 360 !== 0) {
            this._offsetForRotation({
                degrees: this.viewport.getRotation(true),
                useSketch: useSketch,
                saveContext: saveContext
            });
            saveContext = false;
        }
        if (tiledImage.getRotation(true) % 360 !== 0) {
            this._offsetForRotation({
                degrees: tiledImage.getRotation(true),
                point: this.viewport.pixelFromPointNoRotate(
                    tiledImage._getRotationPoint(true), true),
                useSketch: useSketch,
                saveContext: saveContext
            });
        }
    }
Set rotations for viewport & tiledImage
@private
@param {OpenSeadragon.TiledImage} tiledImage
@param {Boolean} [useSketch=false]