To zoom out, just use these 2 functions: Setwindowextex, Setviewportextex

Similar functions: Scalewindowextex, Scaleviewportextex

This example:

Code files:

UnitUnit1;InterfaceusesWindows, Messages, sysutils, variants, Classes, Graphics, Controls, Forms, Dialogs, Comctrls, Stdctrls;typeTForm1 =class(Tform)procedureFormcreate (Sender:tobject);procedureFormdestroy (Sender:tobject);procedureFormpaint (Sender:tobject);procedureFormmousedown (Sender:tobject;      Button:tmousebutton; Shift:tshiftstate; X, Y:integer);procedureFormmousemove (Sender:tobject; Shift:tshiftstate; X, Y:integer);procedureFormmouseup (Sender:tobject;      Button:tmousebutton; Shift:tshiftstate; X, Y:integer);End;varForm1:tform1;Implementation{$R *.DFM}varCvs:tcanvas;  X1,y1:real;  Wx,wy,vx,vy:integer; F:boolean;procedureTform1.formcreate (Sender:tobject);beginCVS: = tcanvas.create; Cvs.  Handle: = GetDC (Handle);  WX: = clientwidth;  WY: = clientheight;  VX: = WX; VY: = WY;End;procedureTform1.formmousedown (Sender:tobject;  Button:tmousebutton; Shift:tshiftstate; X, Y:integer);beginF: = True;  X1: = X; Y1: = Y;End;procedureTform1.formmousemove (Sender:tobject; Shift:tshiftstate; X, Y:integer);beginif  notF ThenExit;  X1: = x/x1;  Y1: = y/y1;  VX: = TRUNC (VX * x1);  VY: = Trunc (VY * y1);  Repaint;  X1: = X; Y1: = Y;End;procedureTform1.formmouseup (Sender:tobject;  Button:tmousebutton; Shift:tshiftstate; X, Y:integer);beginF: = False;End;procedureTform1.formpaint (Sender:tobject);ConstPts:Array[0..2] ofTpoint = ((X: -; Y:Ten), (X: -; Y: -), (X:Ten; Y: -));beginSetmapmode (CVS). Handle, Mm_anisotropic);{The following two functions can only be used in Mm_isotropic or Mm_anisotropic mode}Setwindowextex (CVS). Handle, WX, WY,Nil); Setviewportextex (CVS). Handle, VX, VY,Nil); Cvs. Pen.Width: =3; Cvs.  Pen.color: = clred; Cvs.  Brush.style: = Bscross; Cvs.  Brush.color: = Clsilver; Cvs.  Polygon (pts); Cvs. Ellipse ( -, -, -, the);End;procedureTform1.formdestroy (Sender:tobject);beginCvs. Free;End;End.

Form file:

ObjectForm1:tform1 left =0Top =0Caption =' Form1 'ClientHeight =241ClientWidth =302Color = Clbtnface Font.charset = Default_charset Font.Color = Clwindowtext Font.height =- OneFont.Name =' Tahoma 'Font.style = [] Oldcreateorder = False Position = Podesktopcenter OnCreate = formcreate OnDestroy = Formdestroy Onmou Sedown = Formmousedown OnMouseMove = Formmousemove OnMouseUp = formmouseup OnPaint = Formpaint PixelsPerInch = theTextHeight = -End


Http://www.cnblogs.com/del/archive/2008/06/02/1212382.html

To zoom out, just use these 2 functions: Setwindowextex, Setviewportextex