Read pixels from a HDC - c++

Question

I'm trying to read all pixels on a given area of a HDC to find if a color is present, currently I came up with:
IDirect3DSurface9* pSurface = 0;
p1->CreateOffscreenPlainSurface(1280, 1024,D3DFMT_A8R8G8B8, D3DPOOL_SYSTEMMEM, &pSurface, NULL);
p1->GetFrontBufferData(0, pSurface);
//assert( pSurface );
if( pSurface && GetTickCount() > dwGAKS_Fix )
{
HDC dc;
pSurface->GetDC( &dc );
COLORREF dpurp = D3DCOLOR_ARGB (255,102,0 ,153);
for( DWORD h = 610; h <= 670; h++ )
{
for( DWORD w = 480; w<=530; w++ )
{
COLORREF dwPixel = GetPixel( dc, h, w );
// CString strPixel; strPixel.Format( "Pixel col: %u at: %u X %u", dwPixel, d, i );
//if( dx_Font )
if( dwPixel == dpurp )
{
dx_Font->DrawTextA(NULL, "Shoot", strlen("Shoot"), &pos, DT_NOCLIP, D3DCOLOR_XRGB(0, 255, 0));
}
else
dx_Font->DrawTextA(NULL, "NoShoot", strlen("NoShoot"), &pos, DT_NOCLIP, D3DCOLOR_XRGB(0, 255, 0));
}
}
dwGAKS_Fix = GetTickCount() + 15;
pSurface->ReleaseDC( dc );
pSurface->Release();
But this solution is slow, very slow, I need something somewhat more..uh professional
edit
D3DLOCKED_RECT d3dlocked;
if( D3D_OK == pSurface->LockRect( &d3dlocked, 0, 0 ) )
{
UINT *pixels=(UINT *)locked.pBits;
if(pixels[52+15*1024]&0xFFFFFF00==dpurp)
{
}
pSurface->UnlockRect();
}

Answer 1

GetPixel is always slow. You can get direct access to the bits in the off-screen surface using IDirect3DSurface9::LockRect and then scan through the bitmap yourself, which should be much quicker.
(Edit) Any given pixel (x,y) is the 32 bit value found at:
*(DWORD*)(((BYTE*)d3dlocked.pBits) + y * d3dlocked.Pitch + x * sizeof(DWORD));
You should AND the value with 0x00ffffff to ignore the alpha channel.