draw-circle.lua

-- Aseprite script to draw a circle at a specified (X,Y) with a given radius
-- Written by aquova, 2021
-- https://github.com/aquova/aseprite-scripts

-- Open dialog, ask user for paramters
function userInput()
    local dlg = Dialog()
    -- Create dialog parameters
    dlg:number{ id="x", label="X:", decimals=0 }
    dlg:number{ id="y", label="Y:", decimals=0 }
    dlg:number{ id="radius", label="Radius:", decimals=0 }
    dlg:button{ id="ok", text="OK" }
    dlg:button{ id="cancel", text="Cancel" }
    dlg:show()

    return dlg.data
end

-- Draws the specified circle
function drawCircle(cx, cy, rad)
    local image = app.activeCel.image
    local copy = image:clone()
    local left = cx - rad
    local top = cy - rad
    for x = left, left + 2 * rad do
        for y = top, top + 2 * rad do
            if (x >= 0 and x < copy.width) and (y >= 0 and y < copy.height) then
                local dx = cx - x
                local dy = cy - y
                dx = dx^2
                dy = dy^2
                distSquared = dx + dy
                radSquared = rad^2
                if distSquared <= radSquared then
                    copy:drawPixel(x, y, app.fgColor)
                end
            end
        end
    end
    app.activeCel.image:drawImage(copy)
end

-- Run script
do
    local userCircle = userInput()
    if userCircle.ok then
        drawCircle(userCircle.x, userCircle.y, userCircle.radius)
    end
end