Challenge 14 - Rainbow

[tiagomoreira41]

Hi everyone, a bit late to this one but I enjoyed the challenge, so here is my take on a rainbow.

Instead of outlines, it fills seven concentric circles from the outside in (red first, violet last), then covers the centre with the sky colour and the bottom half with a hill, so only the arcs remain. Changing the variable "band" changes the thickness of each colour.

Code:

' Challenge 14 - Rainbow
GraphicsWindow.Title = "Rainbow"
GraphicsWindow.Width = 640
GraphicsWindow.Height = 380
sky = "LightSkyBlue"
GraphicsWindow.BackgroundColor = sky
GraphicsWindow.PenWidth = 0

colors = "1=Red;2=Orange;3=Yellow;4=Green;5=Blue;6=Indigo;7=Violet;"
cx = 320
cy = 330
r = 280
band = 20

For i = 1 To Array.GetItemCount(colors)
  GraphicsWindow.BrushColor = colors[i]
  GraphicsWindow.FillEllipse(cx - r, cy - r, 2 * r, 2 * r)
  r = r - band
EndFor

' hollow out the centre
GraphicsWindow.BrushColor = sky
GraphicsWindow.FillEllipse(cx - r, cy - r, 2 * r, 2 * r)

' ground
GraphicsWindow.BrushColor = "ForestGreen"
GraphicsWindow.FillRectangle(0, cy, GraphicsWindow.Width, GraphicsWindow.Height - cy)

A nice variation: put the loop in a Sub and call it with a smaller radius and lighter colours (e.g. using GraphicsWindow.GetColorFromRGB) to add a faint second rainbow above the first, with the colour order reversed as in a real double rainbow.