How to use the gemini-core.Image.fromBase64 function in gemini-core

async extendWithPageScreenshot(error) {
        if (!this._config.screenshotOnReject || error.screenshot || this._screenshotTaken) {
            return error;
        }

        this._screenshotTaken = true;
        this._browser.setHttpTimeout(this._config.screenshotOnRejectTimeout);

        try {
            const {value: base64} = await this._browser.publicAPI.screenshot();
            const size = Image.fromBase64(base64).getSize();

            error = _.extend(error, {screenshot: {base64, size}});
        } catch (e) {
            logger.warn(`WARN: Failed to take screenshot on reject: ${e}`);
        }

        this._browser.restoreHttpTimeout();

        return error;
    }
};

.then((screenData) => {
                const image = Image.fromBase64(screenData.value);

                return this._applyCalibration(image);
            });
    }