grayscale - Copying 16bit grascale image to 48 bit rgb image -


i have raw data of 16 bit grayscale image. wanted make 48 bit rgb image copying same value 3 channels. presently i'm doing:

byte *bit=new byte[512*512*6]; int j=-1; int i=0; for(int k=0;k<512*512;k++) {     bit[i]=ptr[++j];     bit[++i]=ptr[j];     bit[++i]=ptr[j];     bit[++i]=ptr[++j];     bit[++i]=ptr[j];     bit[++i]=ptr[j];     i++; }

this code results in yellowish tinge. shifting bits required?

try this:

byte *bit=new byte[512*512*6]; int j=-2; int i=-1; for(int k=0;k<512*512;k++) {     bit[++i]=ptr[++++j];     bit[++i]=ptr[j+1];     bit[++i]=ptr[j];     bit[++i]=ptr[j+1];     bit[++i]=ptr[j];     bit[++i]=ptr[j+1]; }

this following.

1st round:

    bit[0]=ptr[0];     bit[1]=ptr[1];     bit[2]=ptr[0];     bit[3]=ptr[1];     bit[4]=ptr[0];     bit[5]=ptr[1];

2nd round:

    bit[6]=ptr[2];     bit[7]=ptr[3];     bit[8]=ptr[2];     bit[9]=ptr[3];     bit[10]=ptr[2];     bit[11]=ptr[3];

...etc.

actually don't need i , j:

byte *bit=new byte[512*512*6]; for(int k=0;k<512*512;k++) {     bit[6*k]=ptr[2*k];     bit[6*k+1]=ptr[2*k+1];     bit[6*k+2]=ptr[2*k];     bit[6*k+3]=ptr[2*k+1];     bit[6*k+4]=ptr[2*k];     bit[6*k+5]=ptr[2*k+1]; }

the reverse operation (48-bit 16-bit):

byte *bit=new byte[512*512*6]; for(int k=0;k<512*512;k++) {     ptr[2*k]=bit[6*k];     ptr[2*k+1]=bit[6*k+1]; }

if rgb image not grayscale, have calculate luminance of every pixel , copy luminance 16-bit grayscale image:

byte *bit=new byte[512*512*6]; for(int k=0;k<512*512;k++) {     unsigned int r=(bit[6*k]<<8)+bit[6*k+1];     unsigned int g=(bit[6*k+2]<<8)+bit[6*k+3];     unsigned int b=(bit[6*k+4]<<8)+bit[6*k+5];     unsigned int y=(unsigned int)round(0.2126*r+0.7152*g+0.0722*b);      ptr[2*k]=y>>8;     ptr[2*k+1]=y&0xff; }

this code assumes significant byte stored first (big-endian). if use little-endian storage:

byte *bit=new byte[512*512*6]; for(int k=0;k<512*512;k++) {     unsigned int r=(bit[6*k+1]<<8)+bit[6*k];     unsigned int g=(bit[6*k+3]<<8)+bit[6*k+2];     unsigned int b=(bit[6*k+5]<<8)+bit[6*k+4];     unsigned int y=(unsigned int)round(0.2126*r+0.7152*g+0.0722*b);      ptr[2*k+1]=y>>8;     ptr[2*k]=y&0xff; }

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