Unwanted canvas clear
lazarus / 39-Graphics

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user5 · 2014-04-04 17:07

I want to load a bitmap into my form on activation w/o the user having
to press a button. The following loads the bitmap ok but then it
disappears when the procedure ends. Any suggestions?

procedure TForm1.FormActivate();
begin
 MyBitmap := TBitmap.Create;
 MyBitmap.LoadFromFile('c:\temp7\etc');
 Canvas.Draw(0,0,MyBitmap);
 delay(2000);
end;

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Blaazen · 2014-04-04 17:21

Hi,

at first, do not paint anything in OnActivate. Some widgetsets does
not support it at all (Qt, Carbon). Even if you have widgetset which
enables you to paint out of OnPaint method (Windows or GTK2) the
picture will stay there to the next Invalidate only. If you want it
there permanently, there are at least three ways: use TPaintBox +
OnPaint event or TImage, or move the code to Form1.OnPaint event.

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user5 · 2014-04-04 19:54

Thank you so much Blaazen! OnPaint worked out fine but I was wondering
how to send a bitmap to a TImage. I searched previous posts and found
the following but it didn't work:
    image1.Picture.Bitmap.LoadFromFile('c:\temp7\title1.bmp');

Can you tell me how to get MyBitmap into image1? (image1:TImage)

Thanx again. This is a great forum!!!!!

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Blaazen · 2014-04-04 20:15

It works here. I tried both:
Code: [Select]Image1.Picture.LoadFromFile('/media/disk/v1/Lazarus_Qt/l
azarus/images/LazarusForm.bmp');
and
Image1.Picture.Bitmap.LoadFromFile('/media/disk/v1/Lazarus_Qt/lazarus/
images/LazarusForm.bmp');
So I can only guess - some unsupported format of your image? Or typo
in filename?

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user5 · 2014-04-05 10:03

Sorry I didn't reply sooner; I was tired.

I can't get either procedure to work. It compiles ok but when I run it
I get an error message and an assembler window.

This has happened to me before if I didn't have the correct
headers/tpus in the 'uses' section. Do you know what header applies to
"Picture" in Image.Picture.LoadFromFile? Bitmap and
LoadFromFile already work for me when I'm working strictly with
bitmaps. Thanks

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jfmadre · 2014-04-05 11:07

I've tried a simple program with a Timage and a button
procedure TForm1.Button1Click(Sender: TObject);
begin
  Image1.Picture.LoadFromFile('imagefond.jpg');
end;
imagefond.jpg is in the directory of my program

when i click on the button, the image loads without problem.

I had a similar problem whith a software whith opening of assembler
windows.
It occured after my software was trying to read a table over the
dimension declared in a try/finally zone of my soft. The error occured
then in another part of the program and that sems odd.
Solution to find this problem configure the Compiler (Project/Project
options/Compiler options/ and what in french is "Infos de débogage"
then check the options "Intervalle (-Cr)" and "Débordement (-Co)"
Then when runing the soft it stops where the true error is.
Perhaps the same problem ?

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user5 · 2014-04-06 07:31

My bonehead problem is solved. I didn't have a TImage box in my form
to represent image1 and that's why it wouldn't work right. It works
fine now. Thanks to you all for trying to help me. By the way, please
spare a glance at my new posting titled "Bitmap wavefore from .wav
file." I could really use some help there.