Title: A good method to zoom a picture.
Question: How to stretch/zoom a picture using Windows API without much disturbance, and give you a fine result.
Answer:
There is a good way to zoom into a picture with a fine result, the Bitmap routines of windows API give us a good way to stretch Bitmaps,The following code represent the zoom operations, gives you a smooth zoom.
Var
OrignBitmap: TBitmap;//To Save the original bitmap
...
procedure TForm1.OnCreate(Sender: TObject);
begin
OrignBitmap := TBitmap.Create; //Create the original
OrignBitmap.LoadFromFile('C:\Windows\Gone Fishing.bmp')//load the bitmap
end;
Procedure TForm1.Button1Click(Sender: TObject);
Var
TempBitmap: TBitmap; //Temporary picture handler for process
Begin
TempBitmap := TBitmap.Create;
Try
TempBitmap.Height := OrignBitmap.Height + ScrollBar1.Position;
//hint: Scrollbar start from 0
TempBitmap.Width := OrignBitmap.Width + ScrollBar1.Position;
SetStretchBltMode(TempBitmap.Canvas.Handle,STRETCH_HALFTONE);
//set stretch parameters
SetBrushOrgEx((TempBitmap.Canvas.Handle,0,0,nil);
//Rearrange the Brush property for safety reason
//start to stretch the bitmap
StretchBlt(
TempBitmap.Canvas.Handle, //stretch Destination bitmap
0,0,TempBitmap.Width,TempBitmap.Height,//stretch Destination Rectangular
OrignBitmap.Canvas.Handle,//source Rectangular
0,0,OrignBitmap.Width,OrignBitmap.Height, ,//stretch Destination Rectangular
SRCCOPY//stretch parameter
);
//assign the Destination bitmap to the form image
Image1.Picture.Bitmap.Assign(TempBitmap);
//view the image
Image1.Refresh;
Finally
TempBitmap.Free; //Free the Temporary image
End;
End;
procedure TForm1.OnClose(Sender: TObject);
begin
OrignBitmap.Free //free the bitmap
end;