KawaGeo
Joined: 27 Aug 2005
Posts: 191
Location: Calif Mountains
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 Posted: Wed Aug 31, 2005 3:38 am Post subject: Rounding technique required? |
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Hi, everybody!
We know all Lua numbers are floats, no integers available. However, integers are required for the arguments in most Lua Player functions. Hence, rounding technique is necessary. Here is the evidence in the code.
| Code: | -- circleTest.lua by Geo Massar, 2005 (aka kawageo)
PI2 = math.pi * 2
function math.round(num, dp)
local mult = 10^(dp or 0)
return math.floor(num * mult + 0.5) / mult
end
function drawCircleOn(image, x0,y0, radius, segments, color)
-- x0,y0 is the center of the circle
local x1,y1, x2,y2
x1, y1 = x0, y0 + radius
for i = 1, segments do
x2 = math.round(x0 + radius * math.sin(PI2*i/segments))
y2 = math.round(y0 + radius * math.cos(PI2*i/segments))
image:drawLine(x1,y1, x2,y2, color)
x1,y1 = x2,y2
end
end
function magnifyOn(image, mag)
mag = mag or 2 -- 2 times in size by default
local w = image:width()
local h = image:height()
local result = Image.createEmpty(mag*w, mag*h)
for x = 0, w-1 do
for y = 0, h-1 do
result:fillRect(mag*x, mag*y, mag,mag, image:pixel(x,y))
end
end
return result
end
--------------------- main routine -------------------------
green = Color.new(0, 255, 0)
panel = Image.createEmpty(30, 30)
drawCircleOn(panel, 24,5, 5, 4, green) -- a fat diamond
drawCircleOn(panel, 24,24, 5, 12, green) -- a small circle
math.round = function(num, dp) return num end -- no rounding
drawCircleOn(panel, 5,5, 5, 4, green)
drawCircleOn(panel, 5,24, 5, 12, green)
panel = magnifyOn(panel, 4)
left = (480 - panel:width()) / 2
top = (272 - panel:height()) / 2
screen:blit(left, top, panel)
screen.flip()
screen:save "screen.tga"
while true do
screen.waitVblankStart()
end
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The result is displayed below. The symbols on the left side are resulted without rounding. They are badly distorted whereas the symbols on the other side look perfect due to the rounding technique.
The question: Is it our responsibility to make sure all arguments are in pure integers OR should Lua Player take care of the rounding business?
NOTE: The code was tested on Lau Player for Windows. I presumed the same thing for a real PSP. (I don't have a PSP with version 1.5 yet. It is on the way, by the way. :)
_________________
Geo Massar
Retired Engineer |
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