Implement min and max blend modes

https://github.com/SFML/SFML/pull/1756

include/SFML/Graphics/BlendMode.h

@@ -56,9 +56,11 @@ typedef enum
 ////////////////////////////////////////////////////////////
 typedef enum
 {
-    sfBlendEquationAdd,            ///< Pixel = Src * SrcFactor + Dst * DstFactor
+    sfBlendEquationAdd,             ///< Pixel = Src * SrcFactor + Dst * DstFactor
-    sfBlendEquationSubtract,       ///< Pixel = Src * SrcFactor - Dst * DstFactor
+    sfBlendEquationSubtract,        ///< Pixel = Src * SrcFactor - Dst * DstFactor
-    sfBlendEquationReverseSubtract ///< Pixel = Dst * DstFactor - Src * SrcFactor
+    sfBlendEquationReverseSubtract, ///< Pixel = Dst * DstFactor - Src * SrcFactor
+    sfBlendEquationMin,             ///< Pixel = min(Dst, Src)
+    sfBlendEquationMax              ///< Pixel = max(Dst, Src)
 } sfBlendEquation;
 
 
@@ -80,6 +82,8 @@ typedef struct
 CSFML_GRAPHICS_API const sfBlendMode sfBlendAlpha;    ///< Blend source and dest according to dest alpha
 CSFML_GRAPHICS_API const sfBlendMode sfBlendAdd;      ///< Add source to dest
 CSFML_GRAPHICS_API const sfBlendMode sfBlendMultiply; ///< Multiply source and dest
+CSFML_GRAPHICS_API const sfBlendMode sfBlendMin;      ///< Take minimum between source and dest
+CSFML_GRAPHICS_API const sfBlendMode sfBlendMax;      ///< Take maximum between source and dest
 CSFML_GRAPHICS_API const sfBlendMode sfBlendNone;     ///< Overwrite dest with source
 
 

src/SFML/Graphics/BlendMode.cpp

@@ -40,6 +40,14 @@ const sfBlendMode sfBlendAdd = { sfBlendFactorSrcAlpha, sfBlendFactorOne, sfBlen
 const sfBlendMode sfBlendMultiply = { sfBlendFactorDstColor, sfBlendFactorZero, sfBlendEquationAdd,
                                       sfBlendFactorDstColor, sfBlendFactorZero, sfBlendEquationAdd };
 
+////////////////////////////////////////////////////////////
+const sfBlendMode sfBlendMin = { sfBlendFactorOne, sfBlendFactorOne, sfBlendEquationMin,
+                                 sfBlendFactorOne, sfBlendFactorOne, sfBlendEquationMin };
+
+////////////////////////////////////////////////////////////
+const sfBlendMode sfBlendMax = { sfBlendFactorOne, sfBlendFactorOne, sfBlendEquationMax,
+                                 sfBlendFactorOne, sfBlendFactorOne, sfBlendEquationMax };
+
 ////////////////////////////////////////////////////////////
 const sfBlendMode sfBlendNone = { sfBlendFactorOne, sfBlendFactorZero, sfBlendEquationAdd,
-                                      sfBlendFactorOne, sfBlendFactorZero, sfBlendEquationAdd };
+                                  sfBlendFactorOne, sfBlendFactorZero, sfBlendEquationAdd };