camera shading比例

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vendor/mediatek/proprietary/custom/mt6735/hal/D2/camera_3a/isp_tuning_custom.cpp

static MINT32 ratioMapping(MINT32 i4Iso)
{                                                                                                                                            
#define LERP(x, lo_x, lo_y, hi_x, hi_y)
    (((hi_x) - (x))*(lo_y) + ((x) - (lo_x))*(hi_y)) / ((hi_x) - (lo_x))

    static const MINT32 iso[10] =
    {100, 200, 400, 800, 1200, 1600, 2000, 2400, 2800, 3200};

    static const MINT32 rto[10] =
    //{24, 22, 20, 18, 16, 14, 12, 10, 8, 6}; //Tower modify for iso1600 Noise 2014-12-26
    {26, 24, 26, 24, 22, 20, 18, 16, 14, 12};

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