TImage + StretchRatio

I have used this sort of thing in the past. The image is contained in a freely resized panel. The image dimensions are kept in 'ratio'. You can use a hidden image or a tbitmap to do a similar thing. Use StretchDraw if what you want is to copy a bitmap into an image with your own 'ratio'.

Alex

....
var
   w,pgw,
   h,pgh : Integer;
begin
w:=Panel2.ClientWidth;
h:=Panel2.ClientHeight;
pgw:=FirstWidth;
pgh:=FirstHeight;
if w*PgH>h*PgW then w:=trunc(h*PgW/PgH);
if w*PgH<h*PgW then h:=trunc(w*PgH/PgW);
Image1.SetBounds(0,0,w,h);
end;

Epsylon I can't get this image to do anything but stretch.

Cheers
Chris

You are right. The ratio calculations where wrong. Corrected that.


unit ImageEx;
     
interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  ExtCtrls;

type
  TImageEx = class(TImage)
  private              
    { Private declarations }
    FKeepRatio: Boolean;
    procedure SetHeightEx(const Value: Integer);
    procedure SetWidthEx(const Value: Integer);
    function GetHeightEx: Integer;
    function GetWidthEx: Integer;
  protected
    { Protected declarations }
  public
    { Public declarations }
  published
    { Published declarations }
    property KeepRatio: Boolean read FKeepRatio write FKeepRatio;
    property Width: Integer read GetWidthEx write SetWidthEx;
    property Height: Integer read GetHeightEx write SetHeightEx;
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Epsylon', [TImageEx]);
end;

{ TImageEx }

function TImageEx.GetHeightEx: Integer;
begin
  Result := inherited Height;
end;

function TImageEx.GetWidthEx: Integer;
begin
  Result := inherited Width;
end;

procedure TImageEx.SetHeightEx(const Value: Integer);
var ratio: Double;
begin
  if KeepRatio then
  begin
    ratio := Picture.Width / Picture.Height;
    inherited Height := Value;
    inherited Width := Round(inherited Height * ratio);
  end
  else
    inherited Height := Value;
end;

procedure TImageEx.SetWidthEx(const Value: Integer);
var ratio: Double;
begin
  if KeepRatio then
  begin
    ratio := Picture.Height / Picture.Width;
    inherited Width := Value;
    inherited Height := Round(inherited Width * ratio);
  end
  else
    inherited Width := Value;
end;

end.

Be sure that you change the width ot height after you have loaded the image!!!

You app from the other question would look like this:

var
  MyImage: TImageEx;

procedure TForm1.Button1Click(Sender: TObject);
var i: Integer;
begin
  for i := 0 to FileListBox1.Items.Count - 1 do
  begin
    MyImage := TImageEx.Create(self);
    try
      with MyImage do
      begin
        Stretch := True;
        KeepRatio := True;
        Picture.LoadFromFile(FileListBox1.Items.Strings[i]);
        Height := 100;
//        Width := 100;
        Left := xdist;
        Parent := ScrollBox1;
        Top := ydist;
      end;
      xdist := MyImage.Left + MyImage.Width + 10;
    except
      MyImage.Free;
    end;
  end;
end;