cvtColor() segfaults in HSV2RGB_f when src has NaNs (Patch #2020)

When the source image has hues which are NaNs, the sector computed by cvFloor (which should be in the range 0 to 5, inclusive) is a large negative number. This sector is used as an offset for an array, and so leads to invalid memory access and a segfault.

This can be fixed by the following patch:

 1diff --git a/modules/imgproc/src/color.cpp b/modules/imgproc/src/color.cpp
 2index f887837..ae5ab1f 100644
 3--- a/modules/imgproc/src/color.cpp
 4+++ b/modules/imgproc/src/color.cpp
 5@@ -928,12 +928,15 @@ struct HSV2RGB_f
 6                 float tab[4];
 7                 int sector;
 8                 h *= _hscale;
 9+                sector = cvFloor(h);
10+                h -= sector;
11                 if( h < 0 )
12                     do h += 6; while( h < 0 );
13                 else if( h >= 6 )
14                     do h -= 6; while( h >= 6 );
15-                sector = cvFloor(h);
16-                h -= sector;
17+                sector %= 6;
18+                if(sector < 0)
19+                    sector += 6;
20
21                 tab[0] = v;
22                 tab[1] = v*(1.f - s);

Thanks for your time and effort,

Joel.