TBitmap.ScanLine Property

Provides indexed access to each line of pixels.

Pascal

property ScanLine [Row: Integer]: Pointer;

C++

__property void * ScanLine[int Row];

Description

ScanLine is used only with DIBs (Device Independent Bitmaps) for image editing tools that do low-level pixel work.

C++ Examples:

Copy Code

/*
This example shows how to draw directly to a Bitmap.  It
loads a bitmap from a file and then copies it to another
bitmap twice it's size.  Then the two bitmaps are
displayed on the form canvas.
*/

#include <memory>       //for STL auto_ptr class

void __fastcall TForm1::Button1Click(TObject *Sender)
{
  std::auto_ptr<Graphics::TBitmap> Bitmap(new Graphics::TBitmap);
  std::auto_ptr<Graphics::TBitmap> BigBitmap(new Graphics::TBitmap);
  TRGBTriple *ptr, *bigPtr;   // use a (byte *) for pf8bit color
  TPixelFormat pixForm, bigpixForm;
  try
  {
    Bitmap->LoadFromFile("../littlefac.bmp");
    pixForm = Bitmap->PixelFormat;
    bigpixForm  = BigBitmap->PixelFormat;
    Bitmap->PixelFormat = pf24bit;
    BigBitmap->PixelFormat = pf24bit;
    BigBitmap->Height = Bitmap->Height * 2;
    BigBitmap->Width = Bitmap->Width * 2;
    for (int y = 0; y < Bitmap->Height; y++)
    {
      ptr = reinterpret_cast<TRGBTriple *>(Bitmap->ScanLine[y]);
      for (int x = 0; x < Bitmap->Width; x++)
      {
        int bx = x * 2;
        int by = y * 2;
        bigPtr = reinterpret_cast<TRGBTriple *>(BigBitmap->ScanLine[by]);
        bigPtr[bx] = ptr[x];
        bigPtr[bx + 1] = ptr[x];
        bigPtr = reinterpret_cast<TRGBTriple *>(BigBitmap->ScanLine[by + 1]);
        bigPtr[bx] = ptr[x];
        bigPtr[bx + 1] = ptr[x];
      }
    }
    Canvas->Draw(0, 0, Bitmap.get());
    Canvas->Draw(200, 200, BigBitmap.get());
  }
  catch (...)
  {
    ShowMessage("Could not load or alter bitmap");
  }
}

Delphi Examples:

Copy Code

{
This example shows how to draw directly to a Bitmap.  It
loads a bitmap from a file and then copies it to another
bitmap twice it's size.  Then the two bitmaps are
displayed on the form canvas.
}
procedure TForm1.Button1Click(Sender: TObject);
type
  TRGBTripleArray = ARRAY[Word] of TRGBTriple;
  pRGBTripleArray = ^TRGBTripleArray; // use a PByteArray for pf8bit color
var
  x,y : Integer;
  bx, by : Integer;
  BitMap, BigBitMap : TBitMap;
  P, bigP : pRGBTripleArray;
  pixForm, bigpixForm : TPixelFormat;
begin
  BitMap := TBitMap.create;
  BigBitMap := TBitMap.create;
  try
    BitMap.LoadFromFile('littlefac.bmp');
    pixForm := BitMap.PixelFormat;
    bigpixForm := BigBitMap.PixelFormat;
    BitMap.PixelFormat := pf24bit;
    BigBitMap.PixelFormat := pf24bit;
    BigBitMap.Height := BitMap.Height * 2;
    BigBitMap.Width := BitMap.Width * 2;
    for y := 0 to BitMap.Height - 1 do
    begin
      P := BitMap.ScanLine[y];
      for x := 0 to BitMap.Width - 1 do
      begin
        bx := x * 2;
        by := y * 2;
        bigP := BigBitMap.ScanLine[by];
        bigP[bx] := P[x];
        bigP[bx + 1] := P[x];
        bigP := BigBitMap.ScanLine[by + 1];
        bigP[bx] := P[x];
        bigP[bx + 1] := P[x];
      end;
    end;
    Canvas.Draw(0, 0, BitMap);
    Canvas.Draw(200, 200, BigBitMap);
  finally
    BitMap.Free;
    BigBitMap.Free;
  end;
end;