opencv/modules/imgproc/src/opencl/histogram.cl

//                           License Agreement
//                For Open Source Computer Vision Library
//
// Copyright (C) 2010-2012, Institute Of Software Chinese Academy Of Science, all rights reserved.
// Copyright (C) 2010-2012, Advanced Micro Devices, Inc., all rights reserved.
// Copyright (C) 2010-2012, Multicoreware, Inc., all rights reserved.
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// @Authors
//    Niko Li, newlife20080214@gmail.com
//    Jia Haipeng, jiahaipeng95@gmail.com
//    Xu Pang, pangxu010@163.com
//    Wenju He, wenju@multicorewareinc.com
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#ifndef cn
#define cn 1
#endif

#if cn == 16
#define T uchar16
#else
#define T uchar
#endif

__kernel void calculate_histogram(__global const uchar * src, int src_step, int src_offset, int src_rows, int src_cols,
                                  __global uchar * hist, int total)
{
    int lid = get_local_id(0);
    int id = get_global_id(0) * cn;
    int gid = get_group_id(0);

    __local int localhist[BINS];

    for (int i = lid; i < BINS; i += WGS)
        localhist[i] = 0;
    barrier(CLK_LOCAL_MEM_FENCE);

    for (int grain = HISTS_COUNT * WGS * cn; id < total; id += grain)
    {
        int src_index = mad24(id / src_cols, src_step, src_offset + id % src_cols);
#if cn == 1
        atomic_inc(localhist + convert_int(src[src_index]));
#else
        T value = *(__global const T *)(src + src_index);
        atomic_inc(localhist + convert_int(value.s0));
        atomic_inc(localhist + convert_int(value.s1));
        atomic_inc(localhist + convert_int(value.s2));
        atomic_inc(localhist + convert_int(value.s3));
        atomic_inc(localhist + convert_int(value.s4));
        atomic_inc(localhist + convert_int(value.s5));
        atomic_inc(localhist + convert_int(value.s6));
        atomic_inc(localhist + convert_int(value.s7));
        atomic_inc(localhist + convert_int(value.s8));
        atomic_inc(localhist + convert_int(value.s9));
        atomic_inc(localhist + convert_int(value.sA));
        atomic_inc(localhist + convert_int(value.sB));
        atomic_inc(localhist + convert_int(value.sC));
        atomic_inc(localhist + convert_int(value.sD));
        atomic_inc(localhist + convert_int(value.sE));
        atomic_inc(localhist + convert_int(value.sF));
#endif
    }
    barrier(CLK_LOCAL_MEM_FENCE);

    for (int i = lid; i < BINS; i += WGS)
        *(__global int *)(hist + mad24(gid, BINS * (int)sizeof(int), i * (int)sizeof(int))) = localhist[i];
}

__kernel void merge_histogram(__global const int * ghist, __global int * hist)
{
    int lid = get_local_id(0);

    #pragma unroll
    for (int i = lid; i < BINS; i += WGS)
        hist[i] = 0;
    barrier(CLK_LOCAL_MEM_FENCE);

    #pragma unroll
    for (int i = 0; i < HISTS_COUNT; ++i)
    {
        #pragma unroll
        for (int j = lid; j < BINS; j += WGS)
            hist[j] += ghist[mad24(i, BINS, j)];
        barrier(CLK_LOCAL_MEM_FENCE);
    }
}

__kernel void calcLUT(__global uchar * dst, __constant int * hist, int total)
{
    int lid = get_local_id(0);
    __local int sumhist[BINS];
    __local float scale;

    sumhist[lid] = hist[lid];
    barrier(CLK_LOCAL_MEM_FENCE);

    if (lid == 0)
    {
        int sum = 0, i = 0;
        while (!sumhist[i])
            ++i;

        if (total == sumhist[i])
        {
            scale = 1;
            for (int j = 0; j < BINS; ++j)
                sumhist[i] = i;
        }
        else
        {
            scale = 255.f / (total - sumhist[i]);

            for (sumhist[i++] = 0; i < BINS; i++)
            {
                sum += sumhist[i];
                sumhist[i] = sum;
            }
        }
    }
    barrier(CLK_LOCAL_MEM_FENCE);

    #pragma unroll
    for (int i = lid; i < BINS; i += WGS)
        dst[i]= convert_uchar_sat_rte(convert_float(sumhist[i]) * scale);
}