BMP RGB888 To BMP RGB565\RGB555

 #include"BMP.h"

    
  
    
 #define RGB16_BITCOUNT 16
    
 #define RGB24_BITCOUNT 24
    
  
    
 #define RGB565_R 0xf8
    
 #define RGB565_G 0xfc
    
 #define RGB565_B 0xf8
    
 T_U8* RGB24BitTRGB16Bit(T_U8 *src_img,BMP_TYPE bmp_type, DWORD width,DWORD height)
    
 {
    
 	T_U8 *bmp,*dst,*src_dst;
    
 	WORD *temp,K;
    
 	T_U32 B,G,R,g1,b1,r1,dst_line_byte,src_line_byte, i=0, j=0;
    
 	BITMAPFILEHEADER bf;
    
 	BITMAPINFOHEADER bi;
    
 	RGBQUAD pcolorTable[3]={0}; 
    
 	dst_line_byte = WIDTHBYTES(width*RGB16_BITCOUNT);
    
 	src_line_byte = WIDTHBYTES(width*RGB24_BITCOUNT);
    
  
    
 	
    
  
    
 	switch(bmp_type)
    
 	{
    
 	case RGB565: //用Windows图片查看软件显示的是32bit位深，这个是Windows显示的问题 PS显示图像可见  但是偏红2019.9.27
    
 		{
    
 		
    
 			pcolorTable[0].rgbBlue	= 0x00;
    
 			pcolorTable[0].rgbGreen = 0xF8;
    
 			pcolorTable[0].rgbRed	= 0x00;
    
 			pcolorTable[0].rgbReserved	= 0x00;
    
  
    
 			pcolorTable[1].rgbBlue	= 0xE0;
    
 			pcolorTable[1].rgbGreen = 0x07;
    
 			pcolorTable[1].rgbRed	= 0x00;
    
 			pcolorTable[1].rgbReserved	= 0x00;
    
  
    
 			pcolorTable[2].rgbBlue	= 0x1F;
    
 			pcolorTable[2].rgbGreen = 0x00;
    
 			pcolorTable[2].rgbRed	= 0x00;
    
 			pcolorTable[2].rgbReserved	= 0x00;
    
 			
    
 			memset(&bf, 0, sizeof(bf));
    
 			memset(&bi, 0, sizeof(bi));
    
  
    
 			bf.bfType = 0x4d42;
    
 			bf.bfSize = 54 +3*sizeof(RGBQUAD)+ height*dst_line_byte;
    
 			bf.bfOffBits = 54+3*sizeof(RGBQUAD);
    
  
    
 			bi.biSize = 40;
    
 			bi.biWidth = width;
    
 			bi.biHeight = height;
    
 			bi.biPlanes = 1;
    
 			bi.biBitCount = 16;
    
 			bi.biCompression = BI_BITFIELDS;
    
 			bi.biXPelsPerMeter = 0;
    
 			bi.biYPelsPerMeter = 0;
    
 			bi.biClrImportant = 0;
    
 			bi.biClrUsed = 0;
    
 			bi.biSizeImage = height*dst_line_byte;
    
  
    
 			
    
 			bmp = (T_U8*)malloc(54+3*sizeof(RGBQUAD)+height*dst_line_byte);
    
 			if (!bmp)
    
 			{
    
 				return 0;
    
 			}
    
 			memset(bmp, 0, bf.bfSize);
    
 			memcpy(bmp, &bf, 14);
    
 			memcpy(&bmp[14], &bi, 40);
    
 			memcpy(&bmp[54],pcolorTable,3*sizeof(RGBQUAD));
    
  
    
 			src_dst = src_img+54;
    
 			dst		= bmp+54+3*sizeof(RGBQUAD);
    
  
    
 			for(i = 0;i < height;i++)
    
 			{
    
  
    
 				temp = (WORD *)(dst+dst_line_byte*i);
    
 				for(j = 0;j < width;j++)
    
 				{
    
 					B = src_dst[i*src_line_byte+j*3+0];
    
 					G = src_dst[i*src_line_byte+j*3+1];
    
 					R = src_dst[i*src_line_byte+j*3+2];
    
  
    
 					/* Method 1  做了四舍五入，图像效果比没有做四舍五入效果稍好
    
 					R = ((R)+4)>>3;
    
 					G = ((G)+2)>>2;
    
 					B = ((B)+4)>>3;
    
   90. 					if(R > 31) R = 31;
    
 					if(G > 63) G = 63;
    
 					if(B > 31) B = 31;
    
   94. 					//K = ((R << 11)|(G << 5)|(B<<0)); //内存中的保存形式 B分量在低地址
    
 					*temp++ = ((R << 11)|(G << 5)|(B));
    
 					*/
    
 					*temp++ = ((R<<8)&0xF800)|(((G)<<3)&0x7e0)|((B)>>3);
    
 				}
    
 			}
    
 			
    
 		}
    
 		break;
    
 	
    
 	
    
 	case RGB555:
    
 		{
    
 			memset(&bf, 0, sizeof(bf));
    
 			memset(&bi, 0, sizeof(bi));
    
  
    
 			bf.bfType = 0x4d42;
    
 			bf.bfSize = 54 + height*dst_line_byte;
    
 			bf.bfOffBits = 54;
    
  
    
 			bi.biSize = 40;
    
 			bi.biWidth = width;
    
 			bi.biHeight = height;
    
 			bi.biPlanes = 1;
    
 			bi.biBitCount = 16;
    
 			bi.biCompression = BI_RGB;
    
 			bi.biXPelsPerMeter = 0;
    
 			bi.biYPelsPerMeter = 0;
    
 			bi.biClrImportant = 0;
    
 			bi.biClrUsed = 0;
    
 			bi.biSizeImage = height*dst_line_byte;
    
  
    
  
    
 			bmp = (T_U8*)malloc(54+height*dst_line_byte);
    
 			if (!bmp)
    
 			{
    
 				return 0;
    
 			}
    
 			memset(bmp, 0, bf.bfSize);
    
  
    
 			memcpy(bmp, &bf, 14);
    
 			memcpy(&bmp[14], &bi, 40);
    
 			
    
 			src_dst = src_img+54;
    
 			dst		= bmp+54;
    
 			for(i = 0;i < height;i++)
    
 			{
    
 				temp = (WORD *)(dst+dst_line_byte*i);
    
 				for(j = 0;j < width;j++)
    
 				{
    
  
    
 					B = src_dst[i*src_line_byte+j*3+0];
    
 					G = src_dst[i*src_line_byte+j*3+1];
    
 					R = src_dst[i*src_line_byte+j*3+2];
    
  
    
 					// Method 1  做了四舍五入，图像效果比没有做四舍五入效果稍好
    
 					R = ((R)+4)>>3;
    
 					G = ((G)+4)>>3;
    
 					B = ((B)+4)>>3;
    
  
    
 					if(R > 31) R = 31;
    
 					if(G > 31) G = 31;
    
 					if(B > 31) B = 31;
    
 					*temp++ = ((R << 10)|(G << 5)|(B)); //注意最高位保留，总为0
    
 					//method1//
    
  
    
 					//*temp++ = (((R<<7)&0x7c00)|((G<<2)&0x3e0)|(B>>3)); //method 2
    
 					//*temp++ = (((R>>3) << 10)|((G>>3) << 5)|(B>>3));	// method 3
    
  
    
 				}			
    
 			}
    
 		}
    
 		break;
    
 	default:
    
 		break;
    
 	}
    
  
    
 	return bmp;
    
 }