Acces to pixels

Acces to pixels

types of acces to pixels in delphi

using Pixels property ( simple but slow)
- raster scan 1 pass with 2 loops
  procedure TForm1.Draw1Click(Sender: TObject);
  const _width=500; // give that name because "width" means form1.width
  _height=500;
  var x,y:integer;
  begin
  for y:=0 to (_height-1) do
  for x:=0 to (_width-1) do
  form1.Canvas.Pixels[x,y]:=rgb(1,1,1);
  end;
- raster scan 1 pass with 1 loop:
  
  Procedure ...
    const _width=500; // give that name because "width" means form1.width
             _height=500;
             PixelNumberMax= _height*_width;
    var iX,iY:integer;
          PixelNumber:integer;
    begin
      for PixelNumber:=0 to (PixelNumberMax-1) do
        begin
          iX:=0+(PixelNumber mod _width);
          iY:=0+(PixelNumber div _width);
          form1.Canvas.Pixels[iX,iY]:=rgb(0,0,0);
        end; // for pixelNumber ...
    end; // procedure ...
using ScanLine ( more lines to write but very fast)

GetDIBits Function
Requirements :
Header Wingdi.h (include Windows.h)
Library Gdi32.lib
DLL Gdi32.dll

example from Andrew Rybenkov

in the OnCreate procedure
in the OnPaint procedure
in the procedure of OnClick of menu item

directly on canvas of the form
on off-screen bitmap ( it is not seen) and after the drawing display bitmap on the image of the form

How to clear memeory bitmap:
procedure TForm1.Clear1Click(Sender: TObject);
var iX,iY:integer;
begin
FirstLine := bitmap.Scanline[0];
LineLength := (Longint(bitmap.Scanline[1]) - Longint(FirstLine)) div SizeOf(TRGB32);
// clear all points of the bitmap
for iX:=iXmin to iXmax do
For iY :=iYmin to iYMax do
with FirstLine[iY*LineLength+iX] do
begin // all points white
B := 255;
G := 255;
R := 255;
//A := 0;
end;
// display new = blank, white bitmap
Image1.Picture.Graphic:=bitmap;
end;

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Author: Adam Majewski adammaj1-at-o2-dot-pl

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