Well, since art2d is based on zoom able drawings, a direct bitmap equivalent is
not there, since the is fixed in pixels.
Also wxDc is horrible when it comes to displaying bitmaps at a certain size.
A2dImage object is what you can use best. (see canimage.cpp/h)
Now you need to compile Agg into wxart2d for sure.
Since in the wxDcDrawer I use that when it comes to drawing images at angles,
or when zooming.
Look there to see how images are drawn.
The thing is that the a2dImage using an image inside needs to be scaled to be
drawn on the view.
Agg is rather good at that.
Also there is a2dImageRGBA with a2dRgbaImage.
That often better fits the needs for Agg or OpenGl.
wxImage has the alpha stored seperately. While most of the time this does not
fit blitting routines in OS to quickly blit a drawn/anotated buffer to the
screen/openGl buffer etc.
So to reach the speed wanted there might be a need to cache stuff (like a view
specific sized wxImage/wxBitmap from a a2dImage inside a document).
All is possible, just depends on what fits the application.
In principle one can draw on images within wxart2d without problem. If those
images change underneath the surface (video frames), it is just a matter of
setting the a2dImage pending, and the document will be redrawn in idle time.
Even if you are busy drawing, this is no problem, because the tools in general
are redrawn also as part of the document redraw. I.o.w the state of the
application does not mind or get confused.
So if there is idle time ;-) it will happen.
Still not easy :-)
Klaas
From: damateem [mailto:damate...@gmail.com]
Sent: Friday, 29 April, 2011 15:03
To: wxart2d-users_dev@lists.sourceforge.net
Subject: Re: [Wxart2d-users_dev] Annotate live video
The video is coming to our application as a series of bitmaps, so it looks like
wxArt2D is a good choice. What is the best way to implement this using the
wxArt2D framework? I can think of three ways, but maybe there are others.
1. Draw the bitmaps on the background.
2. Draw the bitmaps as the fill for a rectangle.
3. Use a bitmap drawing object. Does this exist?
I'm just looking for a general description of the best method. I can look into
the documentation for details.
What I'd like to do is run the video display in its own thread and have it
constantly updating the displayed image. Then, as fast as possible in the main
thread, I will grab frames from the stream, process them and annotate the video
based on the processing. I know this means that the processing will lag the
live display, but that is acceptable in this case.
You are right, video is complicated, especially if live video is a requirement.
Hardware acceleration can help, but it brings it's own set of
problems...hardware dependence and lack of support for complex annotation, to
name a couple. I've always found the software-only solution to be the best
choice.
Thanks,
David
On 4/28/2011 5:29 PM, klaas.holwerda wrote:
On 04/28/2011 08:30 PM, damateem wrote:
I want to use wxArt2D to draw on live video to mark features in the video. For
instance, I might draw a line where an edge is detected and then update the
line as that edge moves in the video.
wxArt2D can not play video, so live video is played how?
In case you mean you have a sequence of frames in some image format, and want
to add stuff to that, I think makes sense.
It would be great to have resizeable video objects in wxArt2d, but i don't know
how to display a video into a rectangular area. I know all the software to
handle video is available in linux "gstreamer ffmpeg etc.". But i don;t have
the time to dive into that. In principle i think it is possible. But speed is
always an issue. Even in video editing apps, when editing they only display
the video small/low resolution.
With or without wxart2d, video is complicated i think. The real solution is
with hardware acceleration, without that, the software is to busy putting 25
frames per second to the screen in order to be able to do anything else.
So a thread for each video displayed??
I made once an application to show slides as a slideshow with a transition, but
with a walking ticker at the bottom.
The speed of the ticker walking is close to the framerate. Even with OpenGl and
all that is complicated.
Hope this helps you.
Klaas
Before I spend a great deal of time understanding how to use wxArt2D, I thought
I'd get some advice on feasibility.
1. Is this a good use of wxArt2D?
2. Any advice on how best to implement this feature using wxArt2D?
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