predictor.init(
                    fdtRealModelDir,//人脸检测
                    SettingsActivity.fdtCPUThreadNum,
                    SettingsActivity.fdtCPUPowerMode,
                    SettingsActivity.fdtInputScale,
                    SettingsActivity.fdtInputMean,
                    SettingsActivity.fdtInputStd,
                    SettingsActivity.fdtScoreThreshold,//阀值
                    mclRealModelDir,//口罩检测
                    SettingsActivity.mclCPUThreadNum,
                    SettingsActivity.mclCPUPowerMode,
                    SettingsActivity.mclInputWidth,
                    SettingsActivity.mclInputHeight,
                    SettingsActivity.mclInputMean,
                    SettingsActivity.mclInputStd);
        }

中这个 SettingsActivity.fdtInputScale（Input sacle:downScale factor(0.0,1.0)） 参数是什么意思？有什么作用？

来自Android 例子中 (mask-detection-demo)