TBitmap vs CopyRect

[rcloutie]

Hi there,

How to capture a rect from a bitmap to save into another bitmap?

That is, I have an orignal bitmap - Rect(0, 0, 16, 1000);
I want to copy the half bottom to another bitmap - Rect(0, 501, 16, 500);

Anyone knows how to do this?

Thanks in advance

 

[jbpelletier]

Hi,

first, u have a problem with your Trect. Rect(0,501,16,500) have a negative area.. from 501 to 500 = -1

this code should work.. with maybe a little modification of the TRect data..

// bmp_file_source_path='C:\source.bmp';
// bmp_file_dest_path='C:\dest.bmp';
//...
procedure TForm1.Button1Click(Sender: TObject);
var
BMsrc,BMdst: TBitmap;
Rsrc,Rdst: TRect;
begin
BMsrc:=TBitmap.create;
BMsrc.LoadFromFile(bmp_file_source_path);

Rsrc := Rect(0,BMsrc.Height div 2,16,BMsrc.Height);
Rdst := Rect(0,BMsrc.Height div 2,16,BMsrc.Height);

BMdst:=TBitmap.create;
BMdst.Height:=Rdst.Bottom;
BMdst.Width:=Rdst.Right;

//since Rdst=Rsrc u can use only one
BMdst.Canvas.CopyRect(Rdst,BMsrc.Canvas,Rsrc);
BMdst.SaveToFile(bmp_file_dest_path);

BMsrc.free;
BMdst.free;
end;

jb

 

[rcloutie]

Hi jb,

Thanks for reply.
Here's my code:
------------------------------
var
Dest: TRect;
Source: TRect;
Pic: TBitmap;
begin
Dest := Rect(0, 0, 16, picBkg.Height/2);
Source := Rect(0, picBkg.Height/2, 16, picBkg.Height);
Pic := TBitmap.Create;
Pic.Assign(picBkg);
Pic.Canvas.CopyRect(Dest, picBkg.Canvas, Source);
//...
Pic.Free;
end;
------------------------------

Thanks again.

 

[jbpelletier]

Do this mean u still have problems?.. if so.. i modified the code u pasted to make it work on my side (delphi 5), to do what u ask in your first post

here it goes:

// bmp_file_source_path='C:\source.bmp';
// bmp_file_dest_path='C:\dest.bmp';
//...
procedure TForm1.Button1Click(Sender: TObject);
var
BMsrc,BMdst: TBitmap;
Pic: TBitmap;
Source,Dest: TRect;
begin
// "/2" can cause u a problem, u should use "div 2"
Dest := Rect(0, 0, 16, picBkg.Height div 2);
Source := Rect(0, picBkg.Height div 2, 16, picBkg.Height);

Pic := TBitmap.Create;

//Pic.Assign(picBkg); //<----why? this is use to
//copy the hole bitmap .. and as i read, u need only the
//half bothom

//u must set a size to your bitmap named pic
//since u dont assign anythign to it (assign set
//the size automaticly)
Pic.Height:= picBkg.Height div 2;
pic.Width:= 16;

Pic.Canvas.CopyRect(Dest, picBkg.Canvas, Source);
//...
Pic.SaveToFile(bmp_file_dest_path); //to see the result
//...
Pic.Free;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
picBkg:=TBitmap.Create;
picBkg.LoadFromFile(bmp_file_source_path);
end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
picBkg.free;
end;


jb

 

[rcloutie]

>> Do this mean u still have problems?..

No. Problem solved.
Thanks again.