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How to modify the surface data using LockRect

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I'm trying to save render sth. to texture and modify the data before saving it to file.But I found the data incorrect when I modify them.
[source lang="cpp"] LPDIRECT3DSURFACE9 pBackBuffer,pRenderSurface=NULL;
g_pd3dDevice->CreateRenderTarget(width,height,D3DFMT_A8R8G8B8,D3DMULTISAMPLE_NONE,0,TRUE,&pRenderSurface,NULL);
hResult = g_pd3dDevice->GetRenderTarget(0,&pBackBuffer);

g_pd3dDevice->SetRenderTarget(0,pRenderSurface);
g_pd3dDevice->Clear(0, NULL, D3DCLEAR_TARGET, D3DXCOLOR(0,0,0,0), 1.f, 0);
Render();
g_pd3dDevice->SetRenderTarget(0,pBackBuffer);

D3DLOCKED_RECT rect;
if(S_OK == pRenderSurface->LockRect(&rect,NULL,D3DLOCK_NOSYSLOCK))
{
DWORD* pColor = (DWORD*)rect.pBits;

for( UINT y = 0 ; y < height ; y++ )
{
for(UINT x = 0 ; x < width ; x++ )
{
DWORD color = pColor[y*rect.Pitch/4+x];
D3DCOLOR dwcolor = color;
D3DXCOLOR fColor = Color2Value(dwcolor);
if(fColor.a > 0)
{
fColor.r /= fColor.a;
fColor.g /= fColor.a;
fColor.b /= fColor.a;
}
dwcolor = Value2Color(fColor);
pColor[y*rect.Pitch/4+x] = dwcolor;
}
}
pRenderSurface->UnlockRect();
}
D3DXSaveSurfaceToFile(pTexPathName,texFormat,pRenderSurface,NULL,NULL);[/source]
Here is the code.I tried every D3DLOCK flags but none of them work. I also try CreateOffscreenPlainSurface and GetRenderTargetData to copy the surface data to system memory before LockRect.Also Failed.Did I miss Something?

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Can you describe how it failed? Were the contents of the copied image wrong? Were they even close to correct? Did you get any errors or warnings on the debug console?

You have to copy the data in a manner that matches the surface format that you are using, so that may be a possible source of error...

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It runs without errror or any waring,but shows wrong result.
I rendered some colorful particles to the RT and saved it to file.But when I modified the pixel before saving,the colors of particles all change to yelllow(the start color).I guess maybe something happens when surface being wirtten,or the calculation takes too much time during locking rect and cause problem.
[source lang="java"]LPDIRECT3DTEXTURE9 pCopyTexture = NULL;
LPDIRECT3DSURFACE9 pCopySurface = NULL;
g_pd3dDevice->CreateTexture(width,height,0,D3DUSAGE_DYNAMIC,D3DFMT_A8R8G8B8,D3DPOOL_SYSTEMMEM,&pCopyTexture,NULL);
pCopyTexture->GetSurfaceLevel(0,&pCopySurface);
hResult = g_pd3dDevice->GetRenderTargetData(pRenderSurface,pCopySurface);

D3DLOCKED_RECT rect;
if(S_OK == pCopySurface->LockRect(&rect,NULL,D3DLOCK_DONOTWAIT))
{
DWORD* pColor = (DWORD*)rect.pBits;

for( UINT y = 0 ; y < height ; y++ )
{
for(UINT x = 0 ; x < width ; x++ )
{
DWORD color = pColor[y*rect.Pitch/4+x];
D3DCOLOR dwcolor = color;
//D3DXCOLOR fColor = Color2Value(dwcolor);
//if(fColor.a > 0)
//{
// fColor.r /= fColor.a;
// fColor.g /= fColor.a;
// fColor.b /= fColor.a;
// float radio = 1;
// if(fColor.r > radio)
// radio = fColor.r;
// if(fColor.g > radio)
// radio = fColor.g;
// if(fColor.b > radio)
// radio = fColor.b;
// fColor.r /= radio;
// fColor.g /= radio;
// fColor.b /= radio;
// fColor.a /= radio;
//}
//dwcolor = Value2Color(fColor);
pColor[y*rect.Pitch/4+x] = dwcolor;
}
}
pCopySurface->UnlockRect();
}

hResult = D3DXSaveSurfaceToFile(pTexPathName,texFormat,pCopySurface,NULL,NULL);
g_pd3dDevice->SetRenderTarget(0,pBackBuffer);[/source]
Here is my new code,copy data to another surface in system memory and get colorful paticles.And I get yellow paticles with comment code.I'm not sure of D3DLOCK flag here.
Btw,I was trying to get a non-premultiplied alpha texture of 3D rendering scenes.So here I used separate alpha calculating but not good for Add blend mode(src is SRCALPHA,dest is ONE).Any suggestions will be great thankful.

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My mistake.More time spend when modifing data,so the render data for next frame wasn't updated properly, which bothered me 2 days. Edited by Tunisia hawker

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