很简单的问题，各位就看看了

我写的增强亮度的代码，为什么有这种错
Assigning Unsigned long to TColor


代码：
Image1->Picture->Bitmap->Assign(Image1->Picture->Bitmap);
    long r,g,b;
   // TColor color;
    w=Image1->Picture->Width;
    h=Image1->Picture->Height;
     for(long i=0;i<=w-1;i++)
       {  for(long j=0;j<=h-1;j++)
           {
             //color=Image1->Canvas->Pixels[j];
             r=GetRValue(Image1->Canvas->Pixels[j]);
             g=GetGValue(Image1->Canvas->Pixels[j]);
             b=GetBValue(Image1->Canvas->Pixels[j]);
             r=r+10;
             if(r>255)  r=255;
             g=g+10;
             if(g>255)  g=255;
             b=b+10;
             if(b>255)  b=255;
             Bitmap->Canvas->Pixels[j]=RGB(r,g,b);
            }
       }
       Image1->Picture->Bitmap->Assign(Bitmap);