bitmap convert to RGB565 display

转自：http://blog.csdn.net/nitghost/archive/2009/02/23/39256bitmap图片是一个RGB888，每个像素由3个字节组成，R->8bit，G->8bit，B->8bit；

RGB565 的每个pixels是由2字节组成，R->5bit，G->6bit，B->5bit。

转换的思路是取出原图的点，对没个采样进行运算。

#define RGB565_MASK_RED        0xF800
#define RGB565_MASK_GREEN                         0x07E0
#define RGB565_MASK_BLUE                         0x001F

void
 rgb565_2_rgb24(
BYTE
 *rgb24, 
WORD
 rgb565)
{
 //extract RGB
 rgb24[2] = (rgb565 & RGB565_MASK_RED) >> 11;
 rgb24[1] = (rgb565 & RGB565_MASK_GREEN) >> 5;
 rgb24[0] = (rgb565 & RGB565_MASK_BLUE);

 //amplify the image
 rgb24[2] <<= 3;
 rgb24[1] <<= 2;
 rgb24[0] <<= 3;
}

#define RGB565_MASK_RED        0xF800
#define RGB565_MASK_GREEN                         0x07E0
#define RGB565_MASK_BLUE                         0x001F
void rgb565_2_rgb24(BYTE *rgb24, WORD rgb565)
{
 //extract RGB
 rgb24[2] = (rgb565 & RGB565_MASK_RED) >> 11;
 rgb24[1] = (rgb565 & RGB565_MASK_GREEN) >> 5;
 rgb24[0] = (rgb565 & RGB565_MASK_BLUE);
 //amplify the image
 rgb24[2] <<= 3;
 rgb24[1] <<= 2;
 rgb24[0] <<= 3;
}

USHORT
 rgb_24_2_565(
int
 r, 
int
 g, 
int
 b)
{
    return
 (
USHORT
)(((unsigned(r) << 8) & 0xF800) |
            ((unsigned(g) << 3) & 0x7E0)  |
            ((unsigned(b) >> 3)));
}

USHORT rgb_24_2_565(int r, int g, int b)
{
    return (USHORT)(((unsigned(r) << 8) & 0xF800) |
            ((unsigned(g) << 3) & 0x7E0)  |
            ((unsigned(b) >> 3)));
}

USHORT
 rgb_24_2_555(
int
 r, 
int
 g, 
int
 b)
{
    return
 (
USHORT
)(((unsigned(r) << 7) & 0x7C00) |
            ((unsigned(g) << 2) & 0x3E0)  |
            ((unsigned(b) >> 3)));
}

COLORREF
 rgb_555_2_24(
int
 rgb555)
{
    unsigned r = ((rgb555 >> 7) & 0xF8);
    unsigned g = ((rgb555 >> 2) & 0xF8);
    unsigned b = ((rgb555 << 3) & 0xF8);
    return
 RGB(r,g,b);
}

void
 rgb_555_2_bgr24(
BYTE
* p, 
int
 rgb555)
{
    p[0] = ((rgb555 << 3) & 0xF8);
    p[1] = ((rgb555 >> 2) & 0xF8);
    p[2] = ((rgb555 >> 7) & 0xF8);
}

USHORT rgb_24_2_555(int r, int g, int b)
{
    return (USHORT)(((unsigned(r) << 7) & 0x7C00) |
            ((unsigned(g) << 2) & 0x3E0)  |
            ((unsigned(b) >> 3)));
}
COLORREF rgb_555_2_24(int rgb555)
{
    unsigned r = ((rgb555 >> 7) & 0xF8);
    unsigned g = ((rgb555 >> 2) & 0xF8);
    unsigned b = ((rgb555 << 3) & 0xF8);
    return RGB(r,g,b);
}
void rgb_555_2_bgr24(BYTE* p, int rgb555)
{
    p[0] = ((rgb555 << 3) & 0xF8);
    p[1] = ((rgb555 >> 2) & 0xF8);
    p[2] = ((rgb555 >> 7) & 0xF8);
}

#define RGB565_Val(r,g,b) (WORD)((r)<<11 | (g)<<5 | (b))
WORD
 rgb555_2_rgb565(
WORD
 rgb555)
{
   BYTE
 r,g,b;
   FLOAT
 fRate = 63/31;
   //Get R G B
   r = (BYTE
)(((rgb555 >> 7) & 0xF8)>>3);
   g = (BYTE
)((((rgb555 >> 2) & 0xF8)>>3)*fRate);
   b = (BYTE
)(((rgb555 << 3) & 0xF8)>>3);
   *(WORD
 *)pDest = RGB565_Val(RDest,GDest,BDest);
}