Question

VC++大神帮我解释一下这个程序

voidCDib::SaltNoise()
{
int width,height;
DWORD NumberOfPixels;
int x,y;
double fx,fy;
CNoiseDlg dlg;

width=GetDibWidth();
height=GetDibHeight();
NumberOfPixels=DWORD((width*height)/3);

DWORD noisenumber;
if(dlg.DoModal()==IDOK)
{
noisenumber=dlg.m_NoisePercentage*NumberOfPixels/100;
BYTE*PDIBDATA=(BYTE*)::GlobalLock((HGLOBAL) m_pDIBData);
for(DWORDi=1;i<noisenumber;i++)
{
fx=(double)rand()/(RAND_MAX+1);
fy=(double)rand()/(RAND_MAX+1);
x=int(fx*width);
y=int(fy*height);

int position;
position=width*3*y+x*3;
if(rand()>RAND_MAX/2)
{
PDIBDATA[position]=255;
PDIBDATA[position+1]=255;
PDIBDATA[position+2]=255;
}
else
{
PDIBDATA[position]=0;
PDIBDATA[position+1]=0;
PDIBDATA[position+2]=0;
}
}
::GlobalUnlock((HGLOBAL)m_pDIBData);
}

}

Answer 1

看代码是给一个图像生成椒盐噪声的。先使用dlg.m_NoisePercentage*NumberOfPixels/100
噪声率*像素点数 = 噪声点数

使用循环产生三个随机数，if(rand()>RAND_MAX/2)如果前两个随机数小于第三个随机数，那么噪声为255。否则噪声为0.