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Add two buffers

Posted on 1998-11-19
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Last Modified: 2010-04-10
Hi!!

I've two buffers, named buf1 and buf2.

Buf1 contents a RGB file with this structure: R,G,B,R,G,B,...

Buf2 contents a RGBA file with this structure: R,G,B,A,R,G,B,A,...

I want to add these buffers in buf3, so that the result stored in buf3 will be the following:

R,G,B,R,G,B,...

Look that each component of buf3 is calculated:

(example for the first pixel addittion, the A range is from 0 to 1 (0 to 255))

      R=R(buf1)(1-A)+R(buf2)
            G=G(buf1)(1-A)+G(buf2)
            B=B(buf1)(1-A)+B(buf2)

(The first A is used to do the fisrt RGB calculation, the second A is used to do the second RGB calculation, .....)

How can i do that???



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Question by:Sol
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Accepted Solution

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nietod earned 50 total points
ID: 1178212
answer coming.
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Expert Comment

by:nietod
ID: 1178213
typedef unsigned char uByt; // for convenience.

void AddBuffs(uByt *DstPtr,uByt *RGBPtr, uByt *RGBAPtr,int Cnt)
{
   while (Cnt--)
   {
      uByt RGB_R = *RGBPtr++;
      uByt RGB_G = *RGBPtr++;
      uByt RGB_B = *RGBPtr++;
      uByt RGBA_R = *RGRAPtr++;
      uByt RGBA_G = *RGRAPtr++;
      uByt RGBA_B = *RGRAPtr++;
      uByt RGBA_A = *RGRAPtr++;

     *DstPtr++ = RGB_R*(1 - RGBA_A) + RGBA_R;
     *DstPtr++ = RGB_G*(1 - RGBA_A) + RGBA_G;
     *DstPtr++ = RGB_B*(1 - RGBA_A) + RGBA_B;
   }
}

You probably can change the "names" to make the more intelligent.

Let me know if you have any questions.
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Author Comment

by:Sol
ID: 1178214
Hi nietod!!

I'm going to try your answer... ;-D

¿would you suggest me the most simple or efficient way to visualize the final image (buf3) in screen?
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LVL 22

Expert Comment

by:nietod
ID: 1178215
I'm not sure I understand that last question.  Do you mean how do you draw the image on the screen?  If so, it sounds like it is device independant bitmap.  (DIB).  Look at StretchDIBits or at CreateDIBitmap.  Those functions will get you started.  (either way will take about 20 lines of code though.)
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Expert Comment

by:nietod
ID: 1178216
Did this answer your question?
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Author Comment

by:Sol
ID: 1178217
I'm sorry nietod!!

i've been ill for a long time, but now, i'm back again!! ;-D

Let me try the code... You'll have news...

thanks!!
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Author Comment

by:Sol
ID: 1178218
Thank's nietod!!

It works fine!!
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