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ColorHelper.h

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#ifndef __ColorHelper_H__
#define __ColorHelper_H__

#include "StandardLibrary.h"

__forceinline unsigned short AlphaBlend16(
   unsigned short color1, 
   unsigned short color2, 
   unsigned char alpha
   )  
   {
   // These checks are needed to avoid the 16-bit related artefacts we get otherwise
   if (alpha<3)
      {
      return color1;
      }
   if (alpha>252)
      {
      return color2;
      }


   unsigned char invAlpha=255-alpha;
   return 
      ((unsigned short)(
         ((((((unsigned int)color1 & 0xf800)>>11)*invAlpha)+(((unsigned int)color2 & 0xf800)>>11)*alpha)>>8) <<11 |
         ((((((unsigned int)color1 & 0x07e0)>>5 )*invAlpha)+(((unsigned int)color2 & 0x07e0)>>5 )*alpha)>>8) <<5  |
         ((((((unsigned int)color1 & 0x001f)    )*invAlpha)+(((unsigned int)color2 & 0x001f)    )*alpha)>>8)
      ));
   }

__forceinline unsigned int AlphaBlend32(
   unsigned int color1, 
   unsigned int color2, 
   unsigned char alpha
   )
   {
   unsigned char invAlpha=255-alpha;
   return
      (((((color1 & 0x00ff0000)>>16)*invAlpha)+((color2 & 0xff0000)>>16)*alpha)>>8)<<16 |
      (((((color1 & 0x0000ff00)>>8 )*invAlpha)+((color2 & 0x00ff00)>>8 )*alpha)>>8)<<8  |
      (((((color1 & 0x000000ff)    )*invAlpha)+((color2 & 0x0000ff)    )*alpha)>>8)  |
      (0xff000000);
   }

__forceinline unsigned short RGBModulate16(
   unsigned short color1, 
   unsigned short color2
   )
   {
   return
      ((unsigned short)(
         ((((((unsigned int)color1 & 0xf800)>>11)*(((unsigned int)color2 & 0xf800)>>11)))>>5) <<11 |
         ((((((unsigned int)color1 & 0x07e0)>>5 )*(((unsigned int)color2 & 0x07e0)>>5 )))>>6) <<5  |
         ((((((unsigned int)color1 & 0x001f)    )*(((unsigned int)color2 & 0x001f)    )))>>5)
      ));
   }

__forceinline unsigned short RGBAdd16(
   unsigned short color1, 
   unsigned short color2
   )
   {
   #define MIN(x,y) (x<y?x:y)
   return
      ((unsigned short)(
         MIN((((unsigned int)color1 & 0xf800)>>11)+(((unsigned int)color2 & 0xf800)>>11),0x1f) <<11 |
         MIN((((unsigned int)color1 & 0x07e0)>>5 )+(((unsigned int)color2 & 0x07e0)>>5 ),0x3f) <<5  |
         MIN((((unsigned int)color1 & 0x001f)    )+(((unsigned int)color2 & 0x001f)    ),0x1f)
      ));
   }

__forceinline unsigned short RGBSubtract16(
   unsigned short color1, 
   unsigned short color2
   )
   {
   #define MAX(x,y) (x>y?x:y)
   return
      ((unsigned short)(
         MAX((((int)color1 & 0xf800)>>11)-(((int)color2 & 0xf800)>>11),0) <<11 |
         MAX((((int)color1 & 0x07e0)>>5 )-(((int)color2 & 0x07e0)>>5 ),0) <<5  |
         MAX((((int)color1 & 0x001f)    )-(((int)color2 & 0x001f)    ),0)
      ));
   }

__forceinline unsigned short RGB16(
   unsigned char r, 
   unsigned char g, 
   unsigned char b
   )
   {
   return 
      ((unsigned short) (
         ((((unsigned short)r) & 0xf8)<<8) |
         ((((unsigned short)g) & 0xfc)<<3) |
         ((((unsigned short)b) & 0xf8)>>3)
      ));
   }


__forceinline unsigned int RGB32(
   unsigned char r, 
   unsigned char g, 
   unsigned char b
   )
   {
   return
      ((unsigned int) (
         0xff000000  |
         (((unsigned int)r)<<16) |
         (((unsigned int)g)<<8) |
         (((unsigned int)b))
      ));
   }


__forceinline unsigned int RGBA32(
   unsigned char r, 
   unsigned char g, 
   unsigned char b, 
   unsigned char a
   )
   {
   return
      ((unsigned int) (
         (((unsigned int)a)<<24) |
         (((unsigned int)r)<<16) |
         (((unsigned int)g)<<8) |
         (((unsigned int)b))
      ));
   }


// Helper function for converting color values from 32 bit X8R8G8B8 to 16 bit R5G6B5
__forceinline unsigned short RGB32TO16(
   unsigned int color
   )
   {
   return
      ((unsigned short) (
         ((color & 0x00f80000)>>8) |
         ((color & 0x0000fc00)>>5) |
         ((color & 0x000000f8)>>3)
      ));
   }

// Helper function for converting color values from 16 bit R5G6B5 to 32 bit X8R8G8B8
__forceinline unsigned int RGB16TO32(
   unsigned short color
   )
   {
   return 
      (((unsigned int)color & 0xf800)<<8) |
      (((unsigned int)color & 0x07e0)<<5) |
      (((unsigned int)color & 0x001f)<<3) |
      (0xff000000);
   }

__forceinline unsigned int RGB16TO32(
   unsigned short color, 
   unsigned char alpha
   )
   {
   return 
      (((unsigned int)color & 0xf800)<<8) |
      (((unsigned int)color & 0x07e0)<<5) |
      (((unsigned int)color & 0x001f)<<3) |
      (((unsigned int)alpha) <<24);
   }

// Clamp function used by colorhelper functions to clamp input values
__forceinline float CH_CLAMP(float i) 
   { 
   if (i<0.0f)
      {
      i=0.0f;
      }

   if (i>1.0f) 
      {
      i=1.0f;
      }

   return i;
   }

// Helper function for converting from float alpha value in the range 0 to 1 to an 8 bit value in the range 0 to 255
__forceinline unsigned char FLOATTO8(
   float a
   )
   {
   return ((unsigned char)(255.0f*CH_CLAMP(a)));
   }


// Helper function for converting from r, g and b float values in the range 0 to 1 to 16 bit R5G6B5
__forceinline unsigned short FLOATTORGB16(
   float r, 
   float g, 
   float b
   )
   {  
   return
      (((unsigned short)Round(31.0f*CH_CLAMP(r)))<<11) |
      (((unsigned short)Round(63.0f*CH_CLAMP(g)))<<5) |
      (((unsigned short)Round(31.0f*CH_CLAMP(b))));
   }

// Helper function for converting from r, g and b float values in the range 0 to 1 to 32 bit X8R8G8B8
__forceinline unsigned int FLOATTORGB32(
   float r, 
   float g, 
   float b
   )
   {
   return
      (((unsigned int)Round(255.0f*CH_CLAMP(r)))<<16) |
      (((unsigned int)Round(255.0f*CH_CLAMP(g)))<<8) |
      (((unsigned int)Round(255.0f*CH_CLAMP(b)))) |
      0xff000000;
   }

// Helper function for converting from r, g, b and a float values in the range 0 to 1 to 32 bit A8R8G8B8
__forceinline unsigned int FLOATTORGBA32(
   float r, 
   float g, 
   float b, 
   float a
   )
   {
   return 
      (((unsigned int)(255.0f*CH_CLAMP(a)))<<24) |
      (((unsigned int)(255.0f*CH_CLAMP(r)))<<16) |
      (((unsigned int)(255.0f*CH_CLAMP(g)))<<8) |
      (((unsigned int)(255.0f*CH_CLAMP(b))));
   }

__forceinline float RGB16TOFLOATR(
   unsigned short color
   )                       
   {
   return (((float)((color & 0xf800)>>11))/((float)0x1f));  
   }

__forceinline float RGB16TOFLOATG(
   unsigned short color
   )                       
   {
   return (((float)((color & 0x07e0)>>5))/((float)0x3f));
   }

__forceinline float RGB16TOFLOATB(
   unsigned short color
   )                       
   {
   return (((float)((color & 0x001f)))/((float)0x1f));
   }

__forceinline float RGB32TOFLOATA(
   unsigned int color
   )                       
   {
   return (((float)((color & 0xff000000)>>24))/((float)0xff));
   }


__forceinline float RGB32TOFLOATR(
   unsigned int color
   )                       
   {
   return (((float)((color & 0x00ff0000)>>16))/((float)0xff));
   }

__forceinline float RGB32TOFLOATG(
   unsigned int color
   )                       
   {
   return (((float)((color & 0x0000ff00)>>8))/((float)0xff));
   }

__forceinline float RGB32TOFLOATB(
   unsigned int color
   )
   {
   return (((float)((color & 0x000000ff)))/((float)0xff));
   }

#endif /* __ColorHelper_H__ */

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