Use NaN-safe clip function.

This is to prevent more NaN to int conversions like in #21111.

modules/imgproc/src/color_lab.cpp

@@ -2979,9 +2979,9 @@ struct RGB2Luvfloat
         for( ; i < n; i++, src += scn, dst += 3 )
         {
             float R = src[0], G = src[1], B = src[2];
-            R = std::min(std::max(R, 0.f), 1.f);
-            G = std::min(std::max(G, 0.f), 1.f);
-            B = std::min(std::max(B, 0.f), 1.f);
+            R = clip(R);
+            G = clip(G);
+            B = clip(B);
             if( gammaTab )
             {
                 R = splineInterpolate(R*gscale, gammaTab, GAMMA_TAB_SIZE);
@@ -3205,9 +3205,9 @@ struct Luv2RGBfloat
             float G = X*C3 + Y*C4 + Z*C5;
             float B = X*C6 + Y*C7 + Z*C8;
 
-            R = std::min(std::max(R, 0.f), 1.f);
-            G = std::min(std::max(G, 0.f), 1.f);
-            B = std::min(std::max(B, 0.f), 1.f);
+            R = clip(R);
+            G = clip(G);
+            B = clip(B);
 
             if( gammaTab )
             {

modules/imgproc/test/test_color.cpp

@@ -3203,6 +3203,8 @@ TEST(ImgProc_RGB2Lab, NaN_21111)
     src(0, 1) = src(0, 28) = src(0, 82) = src(0, 109) = cv::Vec3f(0, kNaN, 0);
     src(0, 2) = src(0, 29) = src(0, 83) = src(0, 110) = cv::Vec3f(kNaN, 0, 0);
     EXPECT_NO_THROW(cvtColor(src, dst, COLOR_RGB2Lab));
+    EXPECT_NO_THROW(cvtColor(src, dst, COLOR_RGB2Luv));
+    EXPECT_NO_THROW(cvtColor(src, dst, COLOR_Luv2RGB));
 
 #if 0  // no NaN propagation guarantee
     for (int i = 0; i < 20; ++i)