public:
    SkChannelMaskColorFilter(U8CPU redMask, U8CPU greenMask, U8CPU blueMask)
    {
        fMask = SkPackARGB32(0xFF, redMask, greenMask, blueMask);
    }

    virtual void filterSpan(const SkPMColor src[], int count, SkPMColor result[])
    {
        SkPMColor mask = fMask;
        for (int i = 0; i < count; i++)
            result[i] = src[i] & mask;
    }
