Jonathan,
I see I am out of my league here. I'm sure others can give good advice
however - this list is read by a lot of very smart people.
Phil
On 3/6/16 3:36 PM, Jonathan Lynch wrote:
A green-screen extraction on a large image requires millions of
calculations. I am not using a flood-fill based extraction, so that helps a
bit, but it still requires looking at every single pixel and checking to
see if the colors are within a certain range. I want to improve the
algorithm, so that it uses both a color-range comparison and a hue
comparison. Colors that are outside of the color-range comparison but
within the hue comparison probably have splashback from the green screen,
and I could remove some of the green from those pixels - maybe cut the
green component of the pixel in half or something like that.
So, well, that is a whole ton of calculations right there. I really worked
to optimize it in LC, but those optimizations only made a small difference.
An interpreted language would be very unlikely to come close in speed on
raw numerical comparisons like that. From what I understand, even LCB is
more like Java than like C++, so it might be a bit faster than LC, but not
in the range I need. Don't quote me on that.
In general, LC is supposed to be able to to be extended with externals. In
practical terms, this means it should work with the current version of
Visual Studio. I don't have much C++ experience. I was hoping to just
trudge through setting up the external so that I could focus on the
algorithm. Instead, I could not even use the tutorial.
I will try to find a way, though. I am just hoping for advice so that I can
avoid any more blind alleys.
Thanks,
J
On Sun, Mar 6, 2016 at 5:49 PM, Roland Huettmann <roland.huettm...@gmail.com
wrote:
But I would also appreciate a reply, maybe from Peter, which is of general
interest to all of us.
Optimizing is one possibility, then the question about what would LC
Builder accomplish, and then C++, if nothing else does the job fast enough?
I am thinking about some optimisation algorithms which are already
available in C++ and would probably execute not well enough in LCS.
Roland
On Sun, Mar 6, 2016, 23:10 Phil Davis <rev...@pdslabs.net> wrote:
Hi Jonathan,
I would start by seeing if your LC code can be optimized so the time it
takes per screen is acceptable. There are many small changes a person
can sometimes make to code that causes dramatic speed increases.
Or is the bulk of the time spent in areas LC can't address natively?
Maybe that's why you want to go toward an external.
Thanks -
Phil Davis
On 3/6/16 1:55 PM, Jonathan Lynch wrote:
Hello fellow LiveCoders,
I need to write an external and it needs to be fast. It is for
extracting
images from a green screen. I wrote a good algorithm for this in
LiveCode,
but it takes 20-30 seconds to handle all of the data processing. I want
to
use C++ for speed advantages.
I tried following the desktop externals tutorial that LiveCode uses,
but
it
seems that the external generator that LiveCode offers does not work
properly with Visual Studio 2015.
Should I try to find a free version of VS 2010? Should I try to fix the
C++
library files so that they work with VS 2015? Is there some other very
fast
compiled language, like Fortran, that I should try?
I welcome any advice on how to do this.
Thanks,
Jonathan
--
Phil Davis
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