[cello-devel] Stupid Cello Trick #17

Kenny Tilton ktilton at nyc.rr.com
Wed Mar 17 05:44:11 UTC 2004

Well, you all probably figured it out by now, but Cello now has the 
capability to record its own screen shots, as GIF or JPG or PDF or 
whatever. It also can be set to make a "movie" by having it take screen 
shots periodically, with a sequence number differentiating the files. 
With luck we can also persuade ImageMagick to buffer the images (well, 
that works) and then write them all out as an MPG or QT movie (well, 
that almost works because it does write out a lot more data, but the 
movies all end up one frame long no matter what.) Anyway, the JPGs can 
be converted to an animated movie aftwerwards using I/M batch apps such 
as convert.

Even without buffering, Cello can capture about three frames a second 
stopping to write out a JPG each time. Oh, one limitation I am sure can 
be sorted out: I only got it to work capturing the full window. When I 
went to a starting coordinate other than (0 0) things went crazy. But I 
have run into this before, and it is just me not being bright enough to 
understand OpenGL and the pixel math. I punted after two minutes because 
I was trying anyway to capture the whole window (for a moment I tried 
capturing just the spinning hedron).

But if we solve those two problems, damn, iMovie move over. Well, the 
third problem is a huge memory leak, but I am happy anyway that it is 
narrowed down to loading of images from file: once the app is running, 
well, I left it running for a few hours once by mistake and she was 
still spinning happily on my return.

I call it a stupid trick, but I really think this is a fascinating 
feature. partly because it just fell out of the tree into my lap, out of 
the libraries Cello uses. and partly because i think it is the kind of 
capability that will find frequent use, even though none but a few 
obvious ones spring to mind, and it is not  a feature I recall wanting 
in a gui.

Now to work on a nice boring stationary screen shot or two. :)


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