Drawing on a PicShow canvas

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Drawing on a PicShow canvas

Postby wzsun » July 31st, 2003, 2:29 pm

Hi,

Is there a way to create a canvas handle of PicShow so that I can draw anything on it? I'm trying to simulate the Pen tool from Powerpoint so that in my PicShow project... there's a pen tool where I can draw on the canvas.

Any help on how to create the canvas and sample code would be appreciated.

Rgds
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Postby Kambiz » July 31st, 2003, 9:25 pm

You can draw on the bounding rectangle of a transition inside the handler of following events:

OnStart
OnBeforeNewFrame
OnAfterNewFrame

For your case, I think you should draw on the Screen bitmap parameter of the OnAfterNewFrame event.

For drawing outside of the bounding rectangle of a transition there is solution, however you can use BgPicture property to draw on it.

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How do I use BGPicture

Postby wzsun » August 2nd, 2003, 3:31 am

Hi Kambiz,

Thanks for the info. I tried using BGPicture. but couldn't get anything. Sometimes I get the 'Canvas does not allow drawing..'

in my code I tried doingsomething like this:

Canvas := TCanvas.Create;
Canvas.Handle := PicShow.BGPicture.Bitmap.Handle;
..
..
Canvas.LineTo(Pos.X, Pos.Y);


Any help is appreciated..
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Postby Kambiz » August 2nd, 2003, 3:38 am

First you have to set the size of BgPicture.Bitmap, and then you can draw on BgPicture.Bitmap.Canvas.

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Tried it.. but nothing appears

Postby wzsun » August 2nd, 2003, 10:06 am

Hi Kambiz,

Below is a sample code that I did.. somehow there's nothing at all.

To check whether the 'LoadedImage' is set wrongly, I even tried changing the image file to:

PicShow.BgPicture.Bitmap.LoadFromFile('c:\temp\test.bmp');

but still nothing happens. I managed to draw on a TImage.. but somehow I think there's something missing that I have not done.. it's just that I'm not sure where/what it is..

Any help is appreciated....




procedure TMainForm.PenButtonClick(Sender: TObject);
begin
Dragging := False;
PicShow.BgPicture.Bitmap.LoadFromFile(LoadedImage);
Canvas := TCanvas.Create;
Canvas.Handle := PicShow.BgPicture.Bitmap.Handle;
Canvas.Pen.Color := clRed;
Canvas.Brush.Color := clBlue;
Canvas.Brush.Style := bsSolid;
Canvas.Pen.Width := 10;
end;


procedure TMainForm.PicShowMouseMove(Sender: TObject; Shift: TShiftState;
X, Y: Integer);
begin
if Tool = 'Pen' then
begin
if ssLeft in Shift then
begin
if Dragging then
begin
Canvas.LineTo(Pos.X, Pos.Y);
Pos := Point(X, Y);
end;
end;
end;
end;

procedure TMainForm.PicShowMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
if Tool = 'Pen' then
begin
PicShow.Cursor := crDefault;
Dragging := False;
end;
end;


procedure TMainForm.PicShowMouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin

if Tool = 'Pointer' then
begin
if PicShow.Busy then exit;
PicShow.Enabled := False; // To prevent reentrance
try
if ssLeft in Shift then
ShowNextImage;
finally
PicShow.Enabled := True;
end;
end;

// Pen
if Tool = 'Pen' then
begin
if ssLeft in Shift then
begin
Dragging := True;
Pos := Point(X, Y);
Canvas.MoveTo(Pos.X, Pos.Y);
end;
end;
end;
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Re: Tried it.. but nothing appears

Postby Kambiz » August 2nd, 2003, 1:50 pm

wzsun wrote:Hi Kambiz,
procedure TMainForm.PenButtonClick(Sender: TObject);
begin
Dragging := False;
PicShow.BgPicture.Bitmap.LoadFromFile(LoadedImage);
Canvas := TCanvas.Create;
Canvas.Handle := PicShow.BgPicture.Bitmap.Handle;
Canvas.Pen.Color := clRed;
Canvas.Brush.Color := clBlue;
Canvas.Brush.Style := bsSolid;
Canvas.Pen.Width := 10;
end;

I didn't read your entire code because in the above code I saw some serious mistakes:

1. The bitmap handle is not a canvas handle. Instead of assigning PicShow.BgPicture.Bitmap.Handle to the Canvas.Handle, you should assign PicShow.BgPicture.Bitmap.Canvas.Handle to it.

2. You might not create a new canvas, otherwise changes on the canvas will not be reported to the PicShow. Instead of creating a new canvas, you have use PicShow.BgPicture.Bitmap.Canvas. In this case, you do not need to assign any handle to the canvas.handle.

3. I hope you have set the PicShow.BgMode proprty to a right value.

4. The bgPicture is the background image. So, if the image loaded in the Picture property is visible, it will covers the background image.

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