Active Pixel Counter

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Summary:

Stores the number of active pixels on the graphscreen as a variable.

Active Pixel Counter

symaxian 21 Feb 2008 02:48

Adding this as an addition to a program I hope to finish, its simple enough but oh so slow, about a minute for a full scan.

DelVar Z
For(Y,0,62
    For(X,0,94
    Z+pxl-Test(Y,X->Z
    End
End

Y=Y axis
X=X axis
Z=Number of active pixels found

You should be able to easily understand the syntax above but if not, the first For( loop is for the Y axis, the second For( loop is for the X axis. The For( loops result in the pxl-Test scanning every pixel on the graph screen and adding 1 to Z every time a black(active) pixel is found.

Please explain any possible optimization.

Last edited on 21 Feb 2008 03:51 by symaxian Show more

Re: Active Pixel Counter

Xphoenix 21 Feb 2008 03:32

Unless you manually code the coordinates, I think that's the fastest possible routine. You can change the 0->Z to a DelVar Z, but the difference isn't large enough to notice.

Actually, no. Change

If pxl-Test(Y,X
Z+1->Z

to

Z+pxl-Test(Y,X->Z

Last edited on 21 Feb 2008 03:41 by Xphoenix Show more

Re: Active Pixel Counter

symaxian 21 Feb 2008 03:47

Cool, I didn't think you could use commands like pxl-Test in the middle of a boolean equation.
Also cant believe I forgot about the DelVar command.

Re: Active Pixel Counter

burr 21 Feb 2008 05:18

One way you can speed that code up is by cutting down the number of iterations that the inner loop does. For example, you could change it so that it increments by 5 after each iteration, and then have a pxl-Test( command for X, X+1, X+2, X+3, and X+4. Does this make sense?

Re: Active Pixel Counter

symaxian 21 Feb 2008 22:25

Such as below, I didnt fully match it to the graphscreen or test it (just quickly wrote it) so it may be off, but would this really speed it up or just make it a wee bit larger without a change in speed.

DelVar Z
For(Y,0,62
    For(X,-1,18
    Z+pxl-Test(Y,(X+1)->Z
    Z+pxl-Test(Y,(X+2)->Z
    Z+pxl-Test(Y,(X+3)->Z
    Z+pxl-Test(Y,(X+4)->Z
    Z+pxl-Test(Y,(X+5)->Z
    End
End

Last edited on 21 Feb 2008 22:26 by symaxian Show more

Re: Active Pixel Counter

burr 22 Feb 2008 00:02

A good way to think about it is how many times you loop overall. The Y loop goes from 0 to 62, and then for each iteration of the Y loop, the X loop goes from 0 to 94. That means it is 63 (62+0) * 95 (94+0) = 5985. Now, if we cut the inner loop iteration by a fifth (.2), then that would equal 63 * 76 (.8 * 95) = 4788.

Re: Active Pixel Counter

symaxian 22 Feb 2008 03:50

Ya, but does breaking down how many times the loop runs into multiple equations in the loop really speed it up or just complicate it. Your running less loops but more commands per loop so its still running 5985 pxl-Test commands.

Last edited on 22 Feb 2008 03:52 by symaxian Show more

Re: Active Pixel Counter

burr 22 Feb 2008 04:24

It speeds it up, but you're right that it comes at the cost of size. Another thing you can do to speed it up is remove all of the unnecessary storages in the inner loop, and just use Ans+pxl-Test()'s then store that to Z after both loops are done.

:DelVar Z
:For(Y,0,62
:For(X,-1,18
:Ans+pxl-Test(Y,X+1)+pxl-Test(Y,X+2)+pxl-Test(Y,X+3)+pxl-Test(Y,X+4)+pxl-Test(Y,X+5
:End:End
:Ans→Z