Start median rework (#3346)

- Added basic algorithms to `rtengine/median.h`
- Converted first occurrences

rtengine/median.h

@@ -16,26 +16,100 @@
  *  You should have received a copy of the GNU General Public License
  *  along with RawTherapee.  If not, see <http://www.gnu.org/licenses/>.
  */
-#include "rt_math.h"
+
+#pragma once
+
+#include <array>
+#include <algorithm>
+
+#include "opthelper.h"
+
+template<typename T, std::size_t N>
+T median(std::array<T, N> array)
+{
+    const typename std::array<T, N>::iterator middle = array.begin() + array.size() / 2;
+    std::nth_element(array.begin(), middle, array.end());
+
+    return
+        array.size() % 2
+            ? ((*middle + *std::min_element(middle + 1, array.end())) / static_cast<T>(2))
+            : *middle;
+}
+
+template<typename T, typename... ARGS>
+T median(T arg, ARGS... args)
+{
+    return median(std::array<T, sizeof...(args) + 1>{std::move(arg), std::move(args)...});
+}
+
+template<typename T>
+inline T median3(T a, T b, T c)
+{
+    return std::max(std::min(a, b), std::min(c, std::max(a, b)));
+}
+
+template<>
+inline vfloat median3(vfloat a, vfloat b, vfloat c)
+{
+    return vmaxf(vminf(a, b), vminf(c, vmaxf(a, b)));
+}
+
+// See http://stackoverflow.com/questions/480960/code-to-calculate-median-of-five-in-c-sharp
+template<typename T>
+inline T median5(T a, T b, T c, T d, T e)
+{
+    if (b < a) {
+        std::swap(a, b);
+    }
+    if (d < c) {
+        std::swap(c, d);
+    }
+
+    if (c < a) {
+        std::swap(b, d);
+        c = a;
+    }
+
+    a = e;
+
+    if (b < a) {
+        std::swap(a, b);
+    }
+
+    if (a < c) {
+        std::swap(b, d);
+        a = c;
+    }
+
+    return std::min(a, d);
+}
+
+template<>
+inline vfloat median5(vfloat a, vfloat b, vfloat c, vfloat d, vfloat e)
+{
+    const vfloat f = vmaxf(vminf(a, b), vminf(c, d));
+    const vfloat g = vminf(vmaxf(a, b), vmaxf(c, d));
+    return median3(e, f, g);
+}
 
 // middle 4 of 6 elements,
 #define MIDDLE4OF6(s0,s1,s2,s3,s4,s5,d0,d1,d2,d3,d4,d5,temp) \
 {\
-d1 = min(s1,s2);\
-d2 = max(s1,s2);\
-d0 = min(s0,d2);\
-d2 = max(s0,d2);\
-temp = min(d0,d1);\
-d1 = max(d0,d1);\
+d1 = std::min(s1,s2);\
+d2 = std::max(s1,s2);\
+d0 = std::min(s0,d2);\
+d2 = std::max(s0,d2);\
+temp = std::min(d0,d1);\
+d1 = std::max(d0,d1);\
 d0 = temp;\
-d4 = min(s4,s5);\
-d5 = max(s4,s5);\
-d3 = min(s3,d5);\
-d5 = max(s3,d5);\
-temp = min(d3,d4);\
-d4 = max(d3,d4);\
-d3 = max(d0,temp);\
-d2 = min(d2,d5);\
+d4 = std::min(s4,s5);\
+d5 = std::max(s4,s5);\
+d3 = std::min(s3,d5);\
+d5 = std::max(s3,d5);\
+temp = std::min(d3,d4);\
+d4 = std::max(d3,d4);\
+d3 = std::max(d0,temp);\
+d2 = std::min(d2,d5);\
 }
 
 // middle 4 of 6 elements, vectorized
@@ -61,27 +135,27 @@ d2 = vminf(d2,d5);\
 
 #define MEDIAN7(s0,s1,s2,s3,s4,s5,s6,t0,t1,t2,t3,t4,t5,t6,median) \
 {\
-t0 = min(s0,s5);\
-t5 = max(s0,s5);\
-t3 = max(t0,s3);\
-t0 = min(t0,s3);\
-t1 = min(s1,s6);\
-t6 = max(s1,s6);\
-t2 = min(s2,s4);\
-t4 = max(s2,s4);\
-t1 = max(t0,t1);\
-median = min(t3,t5);\
-t5 = max(t3,t5);\
+t0 = std::min(s0,s5);\
+t5 = std::max(s0,s5);\
+t3 = std::max(t0,s3);\
+t0 = std::min(t0,s3);\
+t1 = std::min(s1,s6);\
+t6 = std::max(s1,s6);\
+t2 = std::min(s2,s4);\
+t4 = std::max(s2,s4);\
+t1 = std::max(t0,t1);\
+median = std::min(t3,t5);\
+t5 = std::max(t3,t5);\
 t3 = median;\
-median = min(t2,t6);\
-t6 = max(t2,t6);\
-t3 = max(median,t3);\
-t3 = min(t3,t6);\
-t4 = min(t4,t5);\
-median = min(t1,t4);\
-t4 = max(t1,t4);\
-t3 = max(median,t3);\
-median = min(t3,t4);\
+median = std::min(t2,t6);\
+t6 = std::max(t2,t6);\
+t3 = std::max(median,t3);\
+t3 = std::min(t3,t6);\
+t4 = std::min(t4,t5);\
+median = std::min(t1,t4);\
+t4 = std::max(t1,t4);\
+t3 = std::max(median,t3);\
+median = std::min(t3,t4);\
 }
 
 #define VMEDIAN7(s0,s1,s2,s3,s4,s5,s6,t0,t1,t2,t3,t4,t5,t6,median) \