Blitting a texture

Wana use blitting to copy a texture (source) to the screen (destination).
Got a class (Crect) which has functionality to clip texture.
The aim being to show the texture moving about screen and to show it partially off the screen.

blitting function

Code:

---

void BlitFn ( BYTE *destination, int destWidth, BYTE *source, int sourceWidth, const CRect &sourceRect, int posX, int posY )
{
int sourceHeight;
BYTE alpha;
BYTE *destPnter = destination + ( posX+posY*destWidth)*4;
BYTE *sourcePnter = source;
               
int EndOfLineDestIncrement = ( destWidth - sourceWidth )*4;
               
for ( int posY = 0; posY < sourceHeight; posY++ )
  {
      for ( posX = 0; posX < sourceWidth; posX++ )
          {
        if ( alpha = 255 )
          {
                  memcpy ( destPnter, sourcePnter, 4 );
            }
                                       
        else
            {
                  BYTE blue = sourcePnter [0];
                  BYTE green = sourcePnter [1];
                          BYTE red = sourcePnter [2];
                  BYTE alpha = sourcePnter [3];
                                                                destPnter[0] = destPnter[0] + ( (alpha*(blue-destPnter[0])) >> 8);
                destPnter[1] = destPnter[1] + ( (alpha*(green-destPnter[1])) >> 8);
                  destPnter[2] = destPnter[2] + ( (alpha*(red-destPnter[2])) >> 8);
          }
          }

            sourcePnter += 4;
            destPnter += 4;
               
      }

        destPnter = EndOfLineDestIncrement;
}

---

PROBLEMS:

[1] in the final line of code: 'cant convert type 'int' from type 'BYTE *'
[2] Anybody got any good sites for downloading FREE spaceship textures that could be used for 2D vertical shooter games?

Is this Win32, MFC, DX, OpenGL?
What platform?
What compiler/IDE?

[1] destPnter wants a pointer to a BYTE but you are giving it an int
[2] no