How to draw a perfect circle?

How-to
,
1

Description

LVGL Version…

8.3.9

What I want to…

I want to draw a perfect circle including :

  • the center point : lv_point_t point = {100,100}

  • the radius: int radius = 50

  • the line width: int line_width = 2

Unfortunately, I found that LVGL does not provide a direct interface for drawing circles. I have also tried using the arc to achieve a similar function, but the result was not satisfactory. :upside_down_face:

So what should I do to achieve this in detail?

2

Just create an empty lv_obj. Set its position (100, 100) and size (50?).

Give it a background color/opacity and set its RADIUS style property to either 50 or LV_RADIUS_CIRCLE.

EDIT: just realized you wanted to create a circl with just a line around it. Create an object of size 50, set the radius style property, set background opacity to 0 and then set the border with to 2 and color to whatever you want. See the documentation on styles:

https://docs.lvgl.io/8.4/overview/coords.html#using-styles

1 Like
3

I sincerely appreciate your prompt and effective solution. As a beginner in LVGL programming, I am very grateful for your timely response and assistance in resolving my issues. Thank you very much! :smiling_face_with_three_hearts:

4

If you like to be more adventurous, you can use trigonometry too :slight_smile:

x1 = x + r * Cos (θ)
y1 = y + r * Sin (θ)

where

  • angle θ, goes from 0 deg to 360 degree converted to radian.
  • radian θ = deg θ * (3.14 / 180.0)
  • r is the radius of the circle

corner-angle

5

Yeah! I know that. Just don’t want to build from scratch, (because I’m so lazy… :wink:…

No matter what, I’m still very thankful to you, man.