C＃如何从屏幕中心向外动态绘制圆

Question

So the idea is this: I have an input , as the user types a value I want to draw circles on the screen (see picture).

I want the circles to start from mid screen and if the user types another value to re draw the circles accordingly.

I know how to draw but I am not quite certain how the math for what I want to achieve is done.

PS I wrote code to auto size the circles if the user enters more than the number that fit the screen, but if he enters less than that I want the circles to be drawn from mid outwards.

C# , WinForms

Answer 1

If I understood correctly you are looking for something like this:

var Start = Height / 2 - NumberOfCircles * CircleSize;

for (int i = 0; i < NumberOfCircles; i++)
{
    Draw(Start + (i * CircleSize));
}

PS: Use the variable CircleSize for the actual size of the circle plus some space, and in the function Draw you can manage where the circle is going to be drawn

Answer 2

It's pretty simple maths in the end. Assume

diameter is 100 pixels

Buffer between circles is half-radius (50 pixels)

Width of screen is 800 pixels

Height of screen is 600 pixels

--Initial position:

first position: (width / 2, height / 2 - (circles-1) * (diameter + buffer) / 2))

--All subsequent positions:

next position: (previousposition.x, previousposition.y + diameter+ buffer) 

if you enter 1 circles it would be:

circle 1: (400, 300 - (0 * (radius+buffer)/2 = (400, 300)

If you enter 2 circles it would be:

circle 1: (400, 300 - (1 * (radius+buffer)/2 = (400, 225), circle 2: (400, 225 + 150) = (400, 375)

If you enter 3 circles it would be:

circle 1: (400, 300 - 2*radius+buffer)/2 = (400, 150), circle 2: (400, 150 + 150) = (400, 300), circle 3: (400, 300 + 150) = (400, 450)

... and so on.