I making something that looks like Paint in Delphi. I found how to make zoom function:
procedure SetCanvasZoomFactor(Canvas: TCanvas; AZoomFactor: Integer);
var
i: Integer;
begin
if AZoomFactor = 100 then
SetMapMode(Canvas.Handle, MM_TEXT)
else
begin
SetMapMode(Canvas.Handle, MM_ISOTROPIC);
SetWindowExtEx(Canvas.Handle, AZoomFactor, AZoomFactor, nil);
SetViewportExtEx(Canvas.Handle, 100, 100, nil);
end;
end;
procedure TMainForm.btnZoomPlusClick(Sender: TObject);
var
bitmap: TBitmap;
begin
bitmap := TBitmap.Create;
if(zoomVal < 1000) then
zoomVal:=zoomVal+zoomConst; //zoomVal = 100 by default; zoomConst = 150;
try
bitmap.Assign(MainForm.imgMain.Picture.Bitmap);
SetCanvasZoomFactor(bitmap.Canvas, zoomVal);
Canvas.Draw(MainForm.imgMain.Left,MainForm.imgMain.Top, bitmap);
finally
bitmap.Free
end;
end;
But, the problem is - it zooms only upper left region of image.
Example before zoom: after zoom:
I want to be able to move through all picture area, even after zoom. How can I make this?
You can use SetWorldTransform for every DC. An example implementation for could look like this:
Procedure SetCanvasZoomAndRotation(ACanvas: TCanvas; Zoom: Double;
Angle: Double; CenterpointX, CenterpointY: Double);
var
form: tagXFORM;
rAngle: Double;
begin
rAngle := DegToRad(Angle);
SetGraphicsMode(ACanvas.Handle, GM_ADVANCED);
SetMapMode(ACanvas.Handle, MM_ANISOTROPIC);
form.eM11 := Zoom * Cos(rAngle);
form.eM12 := Zoom * Sin(rAngle);
form.eM21 := Zoom * (-Sin(rAngle));
form.eM22 := Zoom * Cos(rAngle);
form.eDx := CenterpointX;
form.eDy := CenterpointY;
SetWorldTransform(ACanvas.Handle, form);
end;
Procedure ResetCanvas(ACanvas: TCanvas);
begin
SetCanvasZoomAndRotation(ACanvas, 1, 0, 0, 0);
end;
You might define Zoom, X Y Offest and rotation for the desired Canvas before painting. In your case you would choose a Zoom, paint to canvas and on scrolling in/decrease the value for X and/or Y and call the procedure with the same zoom again and paint your graphic.
EDIT To show how to use the procedure. This code
procedure TForm2.PaintBox1Paint(Sender: TObject);
var
i, w, h: Integer;
C: TCanvas;
begin
C := TPaintBox(Sender).Canvas;
w := TPaintBox(Sender).Width;
h := TPaintBox(Sender).Height;
for i := 0 to 9 do
begin
SetCanvasZoomAndRotation(C, 1 + i / 5, i * 36, w div 2, h div 2);
C.Draw(0, 0, Image1.Picture.Graphic);
C.Brush.Style := bsClear;
C.TextOut(50, 0, Format('Hi this is an example %d', [i]));
end;
end;
is used to display following result:
As response to your comment, how to use it with trackbars, you implement something like
procedure TForm2.FormCreate(Sender: TObject);
begin
DoubleBuffered := true;
end;
procedure TForm2.PaintBox1Paint(Sender: TObject);
var // a Paintbox aligned alClient
C:TCanvas;
begin
TrackBarHorz.Max := Round(Image1.Picture.Graphic.Width * SpinEditZoomInPercent.Value / 100 - TPaintBox(Sender).Width);
TrackBarVert.Max := Round(Image1.Picture.Graphic.Height * SpinEditZoomInPercent.Value / 100 - TPaintBox(Sender).Height);
C := TPaintBox(Sender).Canvas;
SetCanvasZoomAndRotation(c , SpinEditZoomInPercent.Value / 100, 0
, - TrackBarHorz.Position
, - TrackBarVert.Position);
C.Draw(0,0,Image1.Picture.Graphic);
end;
procedure TForm2.SpinEditZoomInPercentChange(Sender: TObject);
begin
PaintBox1.Invalidate;
end;
procedure TForm2.BothTrackbarsEvent(Sender: TObject);
begin
PaintBox1.Invalidate;
end;