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Drawing circles - LED matrix

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atferrari

Well-Known Member
Given a matrix of LEDs (vertical columns / horizontal rows) I plan to draw circles with extreme LEDs staying from 1 to 8 positions from the center (shown in gray).

I came with these 8 distributions and believe they are the best approach to a circle. For eventual reference, consider the start at the top, in the column containing the center position albeit the circle is "drawn" on/off at once. Any could coexist with one or more, always concentric.

Point in question is the number / relative position of the LEDs to the center. Distance between rows / columns is fixed so out of question.

Comments appreciated.

Circles 1 to 8 - standard matrix.png
 

NorthGuy

Well-Known Member
If you can control brightness of individual LEDs, you can do anti-aliasing, which should considerably improve the results.
 

atferrari

Well-Known Member
If you can control brightness of individual LEDs, you can do anti-aliasing, which should considerably improve the results.
Hola North,

Gracias for replying.

Brightness control was in my plans but actually as part of some effects (undefined yet).

Could you elaborate briefly?
 

NorthGuy

Well-Known Member
Could you elaborate briefly?
You light the pixels with different brightness to create an appearance of a smooth circle. Pixels directly on the circle are full brightness, pixels outside the circle are dark. Pixels on the border have intermediary brightness.

Copy a letter from your screen, paste the picture into paintbrush and magnify as much as you can. You will see pixels of different brightness (neglect the colors). This is how they make letters look smooth on a pixelated display.
 

ronsimpson

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Most Helpful Member
Could you elaborate briefly?
In this case; There are four LEDs that are a long distance from another. North, South, East, West.
There are four pair of LEDs that should have the brightness reduced. They will appear too bright.
upload_2016-7-24_9-29-10.png
 

atferrari

Well-Known Member
You light the pixels with different brightness to create an appearance of a smooth circle. Pixels directly on the circle are full brightness, pixels outside the circle are dark. Pixels on the border have intermediary brightness.

Copy a letter from your screen, paste the picture into paintbrush and magnify as much as you can. You will see pixels of different brightness (neglect the colors). This is how they make letters look smooth on a pixelated display.
Got it, North. What they do with certain fonts in printers. Don Lancaster's explanations was the 1st time I read about that.

In my case I did not relate it to my circles; I expected to go away with the thinnest possible lines. For that type of smoothing I will need thicker "strokes". Food for thought. Now aware of Xiaolin Wu as well.

Gracias NG.
 

atferrari

Well-Known Member
In this case; There are four LEDs that are a long distance from another. North, South, East, West.
There are four pair of LEDs that should have the brightness reduced. They will appear too bright.
View attachment 100578
Yes Ron. A simpler alternative to the smoothing suggested by NorthGuy. A simpler algorithm as well!

Gracias for replying.
 
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