Speed up the color operation?

MyFlashLabs

I am reading the color of pixels and extract the red/green/blue channels like below:

var pxColor:uint = _bmd.getPixel(x, y);
var red:uint = pxColor >> 16 & 0xFF;
var green:uint = pxColor >> 8 & 0xFF;
var blue:uint = pxColor & 0xFF;

Extracting colors like above will take time. A few milliseconds matter! and because I am doing above in a loop for many pixels, my speed tests are showing that if I can find a faster way to speed up the above operation, the whole process will complete sooner.

I'm very bad with understanding colors and thought to ask here to see if there's any equivalent way to get the same result but faster?

joshtynjala

The slowest part of your code is probably the function call for getPixel(). The extraction of the RGB values from the color should be very fast.

Maybe you can try calling getVector() before your loop, and use that result instead of the repeated calls to getPixel(). Array/vector index access should be much faster than a function call.

eykatz

Also, If possible, consider scanning only N pixels every frame, and let the operation run through multiple frames.

bwhiting

Josh is bang on here but the context matters.
I.e. how big the bitmapdata is. How often is it changing. Are you checking every pixel. Are you doing it every frame. Could it happen on a number of workers and be processed in parallel.
Get vector is probably the best place to start. Use can also make use of fast byte array access also in some situations which is faster than bytearray [] style access.

MyFlashLabs

Great ideas. Thanks. I included these and everything else I could think of and also moved the process into a standalone worker... and a 25 minute process is now down to 5 minutes. which is not only awesome but also the best performance I've seen in other languages! 💪

bwhiting

The only other thing I could think of would be to use the GPU but that would really depend on what you were trying to do with the data as to if it would be possible.
Great work on the optimisation!