image component flickers during move

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4 total messages Started by Nicholas Gessler Tue, 07 Aug 2001 15:18

#1231

Author: Nicholas Gessler
Date: Tue, 07 Aug 2001 15:18

19 lines
1658 bytes

Using the image component, I was trying to make the image glide (float)
across the screen.  So I set up a timer that incrementally moves the top and
left properties of the image.  The timer quits when the image reaches the
screen center (it is disabled).  This all works, but the image flickers as
it passes over other stationary images.  The image is a .bmp and is
transparent.  Can anyone tell me how to program flicker-free movement?  I am
trying, to some extent, to emulate some of the emulation in Flash.

void __fastcall TForm1::TimerGlideTimer(TObject *Sender)
{
   if (x>280) TimerGlide->Enabled=false;
   x=x+5;
   y=y+4;
   Form1->ImageModel->Left=x;
   Form1->ImageModel->Top=y;
}

Thanks for your help,
Nick

Re: image component flickers during move

#1232

Author: Corey Murtagh
Date: Tue, 07 Aug 2001 19:57

35 lines
2545 bytes

Nicholas Gessler <gessler@ucla.edu> wrote in message
news:3b70065b_1@dnews...
> Using the image component, I was trying to make the image glide (float)
> across the screen.  So I set up a timer that incrementally moves the top
and
> left properties of the image.  The timer quits when the image reaches the
> screen center (it is disabled).  This all works, but the image flickers as
> it passes over other stationary images.  The image is a .bmp and is
> transparent.  Can anyone tell me how to program flicker-free movement?  I
am
> trying, to some extent, to emulate some of the emulation in Flash.

I spent a while trying way back, but eventually gave up on using multiple
TImage objects.  These days I use TBitmap objects to hold images and draw my
screen into, then CopyRect to move the data to a TPaintBox on-screen.  It's
a bit more work, but since all of the image compositing is done off-screen
there's little or no flicker - none if it's done right.

Here's what I'd suggest...

Create a Graphics::TBitmap for each image you're using, one for your
composite image, and a final one for the screen image.  When the on-screen
image needs to change, clear the composite bitmap and draw all of the images
onto it.  When that's done copy the composite to the screen bitmap, then
update the TPaintBox.  Don't forget to handle the TPaintBox's OnPaint
event - that's the reason for seperate composite and screen bitmaps.

If that doesn't eliminate 99% of your screen flicker immediately then
there's something strange happening :>


--
Corey Murtagh
The Electric Monk
"Quidquid latine dictum sit, altum viditur."

Re: image component flickers during move

#1233

Author: Van Tumour
Date: Wed, 08 Aug 2001 18:52

17 lines
1422 bytes

If you decide to do it the way Corey suggests, then I recommend making use
of the following free VCL component package

'VTI Super-Graphics package'
http://members.tripod.co.uk/vantumour/products.htm

It contains an enhanced TBitmap and TPaintBox  for exactly this sort of
stuff.

HTH

--
Van Tumour
----------------------------------
vt@vantumour.com
http://www.vantumour.com
----------------------------------

Re: image component flickers during move

#1234

Author: Nicholas Gessler
Date: Fri, 10 Aug 2001 05:11

5 lines
1110 bytes

Thanks Corey and Van,
I'm trying to build a small collection of sample applications for my
students in Geography.  Your help has been invaluable.
Best,
Nick

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