What's the most quickly algorithm to gray an image?

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in the name of god

hi every body

i want to write an image processing project that i need quickly algorithm, but the code that i used is low. my code is :

C++

CImage i;
unsigned char gray[1000][1000];
i.Load(_T("1.jpg"));
for(int x=0;x<i.GetWidth();x++){
   for(int y=0;y<i.GetHeight();y++){
      COLORREF color=i.GetPixel(x,y);
      int ave=(GetRValue(color)+GetGValue(color)+GetBValue(color))/3;
      gray[x][y]=ave;
   }
}

can everyone help me?
thanks in advance

Posted 1-Feb-14 20:53pm

Mahdi Nejadsahebi

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Kornfeld Eliyahu Peter · Answer 1 · 2014-02-01T21:54:00

Solution 1

Look here - it has a slow and fast method...
Converting Color to Grayscale Using ATL::CImage[^]
Here also has a more theoretic explanation of different approaches - it seems to me that avarage method should perform best...
http://www.johndcook.com/blog/2009/08/24/algorithms-convert-color-grayscale/[^]

Posted 1-Feb-14 21:54pm

Kornfeld Eliyahu Peter

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Mahdi Nejadsahebi 3-Feb-14 1:45am

dear friend
thanks for your answer
but i want to know what code is more faster from "GetPixel()" and "GetRValue()" functions to get color from image.

Kornfeld Eliyahu Peter 3-Feb-14 2:09am

I see...
In that case you may consider one of these:
1. CImage::GetBits - you will get a pointer to the bits of the image as a continuous byte array, and you can move on it only by calculating indexes
2. CImage::GetColorTable/CImage::SetColorTable - it will enable you edit only the color table of the image without hitting the pixels at all