C++ Scanline functionality in embarcadero's builder

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1.50/5 (2 votes)

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Um.. I thought I understood scan line... but when I step through the code, the source pointer remains empty and nothng gets transferred. I you have any advice, I'm listening.
this is the core of my code, I'm hoping to do stuff to the pixels between reading and writing, but this part doesn't work, an I don't know why.

C++

void TDriverFrm::MoveBmp(Graphics::TBitmap *Dest, Graphics::TBitmap *Source, TColor Color)
{
  int x,y;
  TRGBTriple *Sbyte, *Dbyte;

  for(y=0; y<TILEDIM; y++){
    Sbyte = (TRGBTriple *)Source->ScanLine[y];
    Dbyte = (TRGBTriple *)Dest->ScanLine[y];
    for(x=0; x<TILEDIM; x++){
      Dbyte[x] = Sbyte[x];
    }
  }
}

Posted 5-Jan-16 9:49am

completeknowitall

Updated 3-Dec-17 8:25am

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Dave Kreskowiak 5-Jan-16 16:07pm

You're going to have to define "doesn't work". That tells us nothing. What is the code supposed to do exactly and what is it actually doing?

A scan line is just the array of bytes that make up a single row of pixels in a bitmap image.

completeknowitall 5-Jan-16 17:04pm

sorry, I thought it was obvious ( I guess it never is ) I'm trying to copy pixel data pixel by pixel from one bitmap to another using the scanline funtion. the line:

Sbyte = (TRGBTriple *) Source->Scanline[y];

assigns the pointer to the correct line (i guess) and the line

Dbyte[x] = Sbyte[x];

should transfer RGB data to the destination bitmap. however, my debugger shows that

Sbyte[0] ... Sbyte[2] contain all 0x00
(or rather '\0' because it thinks it's a char *)

I was hoping someone with exp. in scanline could point out the "obvious" mistake I made.

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Dave Kreskowiak · Accepted Answer · 2016-01-05T13:04:00

Solution 2

I haven't touched C++ in about 5 years and I've never even heard of Embarcadero, but... it looks like your cast is being applied to the wrong item. Shouldn't it be something like:

C

Sbyte = (TRBGTriple *)(Source->scanline[y]);

Posted 5-Jan-16 13:04pm

Dave Kreskowiak

Comments

completeknowitall 18-Jan-16 14:48pm

You are right. I have learned from you.
I owe you, I owe you money.

Thank you.