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Directx 9 c++ getting colours of pixels from a texture

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Hi I would like to get all the pixel colours of a texture / surface somehow without using a GDI function like GetPixel(). Is this possible? I searched on msdn and there is a way to lock a surface, can I use this to somehow get the pixels from my texture? thanks, r_bewick

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This is XNA 3.0/C# but you should be able to do something similar.

private Rectangle zone;
Texture2D tex;
Color[] imgData = new Color[zone.Height * zone.Width];
tex.GetData<Color>(0, zone, imgData, 0, imgData.Length);

The rectangle can represent the entire texture or a subset for cropping.

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Its a bit different in native code. Something like:

HRESULT hr=texture-&gt;LockRect(0,&locked,NULL,0);

If that is successful it returns a structure 'locked' that contains info about the texture. You can now obtain a pointer that points to the colour in the top left of the image:

BYTE *bytePointer=(BYTE*)locked.pBits;

Now you have a pointer to all the data, you need to interpret it as colours. If you know it is a 32 bit format you can extract the data by going along the horizontal (x coordinate) reading the values 4 bytes at a time. One gotcha is that a line of data in memory may be longer than the width of the image - this is due to padding for optimisation purposes. So the memory width of a line may actually be different than the image width. You can find it though by looking at locked.Pitch, so:

for (DWORD y=0;y&lt;surfaceDesc.Height;y++)
for (DWORD x=0;x&lt;surfaceDesc.Width;x++)
DWORD index=(x*4+(y*(locked.Pitch)));

// Blue
BYTE b=bytePointer[index];

// Green
BYTE g=bytePointer[index+1];

// Red
BYTE r=bytePointer[index+2];

// Alpha
BYTE a=bytePointer[index+3];

And that's it. Once you have finished you must unlock the texture:


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