optimized cv::calcHist

modules/imgproc/src/histogram.cpp

@@ -1410,9 +1410,12 @@ static bool ocl_calcHist1(InputArray _src, OutputArray _hist, int ddepth = CV_32
 {
     int compunits = ocl::Device::getDefault().maxComputeUnits();
     size_t wgs = ocl::Device::getDefault().maxWorkGroupSize();
+    Size size = _src.size();
+    bool use16 = size.width % 16 == 0 && _src.offset() % 16 == 0 && _src.step() % 16 == 0;
 
     ocl::Kernel k1("calculate_histogram", ocl::imgproc::histogram_oclsrc,
-                  format("-D BINS=%d -D HISTS_COUNT=%d -D WGS=%d", BINS, compunits, wgs));
+                   format("-D BINS=%d -D HISTS_COUNT=%d -D WGS=%d -D cn=%d",
+                          BINS, compunits, wgs, use16 ? 16 : 1));
     if (k1.empty())
         return false;
 
@@ -1420,8 +1423,7 @@ static bool ocl_calcHist1(InputArray _src, OutputArray _hist, int ddepth = CV_32
     UMat src = _src.getUMat(), ghist(1, BINS * compunits, CV_32SC1),
             hist = ddepth == CV_32S ? _hist.getUMat() : UMat(BINS, 1, CV_32SC1);
 
-    k1.args(ocl::KernelArg::ReadOnly(src), ocl::KernelArg::PtrWriteOnly(ghist),
-            (int)src.total());
+    k1.args(ocl::KernelArg::ReadOnly(src), ocl::KernelArg::PtrWriteOnly(ghist), (int)src.total());
 
     size_t globalsize = compunits * wgs;
     if (!k1.run(1, &globalsize, &wgs, false))

modules/imgproc/src/opencl/histogram.cl

@@ -37,11 +37,21 @@
 //
 //
 
+#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);
+    int id = get_global_id(0) * cn;
     int gid = get_group_id(0);
 
     __local int localhist[BINS];
@@ -50,10 +60,30 @@ __kernel void calculate_histogram(__global const uchar * src, int src_step, int
         localhist[i] = 0;
     barrier(CLK_LOCAL_MEM_FENCE);
 
-    for (int grain = HISTS_COUNT * WGS; id < total; id += grain)
+    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);
-        atomic_inc(localhist + (int)src[src_index]);
+#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);