_initState() {
        this._state = {
            anisotropy: 1,
            generateMipmap: false,

            wrapS: null,
            wrapT: null,
            minFilter: null,
            magFilter: this.gl.LINEAR, // default to gl.LINEAR
        };
    }
Init per-texture parameters state
     Called on init and on context restoration to force parameters settings
*