Lua Programming Help Thread

[radioactive_X]

Does alpha in images work in windows lua player?
Because in mine it doesn't, but the same file works on my PSP.

Is it my windows lua player or do they all do this.

To elaborate it works somewhat, but only in fully transparent areas, those semi transparent areas are drawn solid.

++EDIT++
One more question.

Does bliting something outside the 0-480, 0-270 coordinates acutely blit it to the offscreen buffer?

Is it necessary to use something like

if x >= 0 and x < 480 then
         screen:blit(x,y,image)
end

or is it handled internally buy the blit function?

[myschoo]

ill answer the first question: lua player windows has some problems with alpha layer, for me color (255,255,255,127) dint work in PC but worked in PSP

[PSPJunkie_]

As, for the second, blit where ever you want. You just won't be able to see it if it is past 480(x) or 272(y).

[Merick]

when blitting offscreen using negative coords, if you go more than the screen size the image won't be blitted.

[PSPJunkie_]

That is lua specific correct? For that is not the case in C.

[KleptoOne]

The lua blit function was written in C, so technically it does do it in C. But it is an interesting question, does lua skip the blitting process automatically if an object is offscreen, or does it still allocate resources to something that the user will never see?

[PSPJunkie_]

Actually, LuaPSP was written in C++. And it is fairly easy. Just check if the x and y of the image are on screen, then blit if they are. I did it in a tile engine I made.

[radioactive_X]

So I should use the above code?
I'm sorry your answers are a little conflicting.

Merick says that it won't be blited PSPJunkie says it will be blited

Because if its like Merick is saying an image wont be blited even if only the top left part went out of screen (like text does) or does the blit function use a buffer zone with image:width() and height() to make sure that doesn't happen?

I'll do some test when I have some time.

++EDIT++

I just did this test

test = Image.load("bg.png")

timer= Timer.new()
timer:start()

for i = 1,100000 do
	screen:blit(-1000,-1000,test)
end

timer:stop()

screen:print(100,100,timer:time(),Color.new(255,255,255))
screen.flip()
screen.waitVblankStart(100)

And what happened is:
Whole image out of screen(100.000): 32-41
One pixel of image in screen(100.000): 47-63
Quarter of image displayed(only 10.000 repetitions):4267
Whole image in screen(only 10.000 repetitions): 19128
(I did this on my PC)

Does this mean that whenever we use blit it affects performance per pixel show, because I think the first two times were just the counter counting to 100.000.

Any thoughts?

[Merick]

what I'm saying is that if you had an image that was larger than the screen size, let's say 500x500, if you tried to blit it at -479 x -271 the image would be blitted and you would still be able to see the part of the image that's supposed to be in the visible screen area, but if you went further than that, -500 x -500, the image will not be blitted.

even if it doesn't show the image, it does take a small amount time for the lua player do it's internal checks on the image, so yes you should use a check to see if the image will be shown.

if x >= -image:width() and -image:width() > -480 then
         screen:blit(x,y,image)
end

----

In this code, can anyone tell me why my angle is off by 90 degrees?

function degree() return math.rad(math.abs(math.deg(math.atan2(pad:analogX(),pad:analogY()))-180)) end
function newx(x, radius, radian) return (x + math.cos(radian)*radius) end
function newy(y, radius, radian) return (y + math.sin(radian)*radius) end

white = Color.new(255,255,255)
blue  = Color.new(0,0,255)
red   = Color.new(255,0,0)

aim = -1
pad = Controls.read()

x = 240
y = 136
x2 = x
y2 = y

while not pad:square() do

	pad = Controls.read()
	if math.abs(pad:analogX()) > 25 or math.abs(pad:analogY()) > 25 then
		aim = degree()
	end
	
	if aim ~= -1 then
		x2 = newx(x, 20, aim)
		y2 = newy(y, 20, aim)
	end

	screen:clear()
	screen:drawLine(x, y, x2, y2, red)
	screen:fillRect(x, y, 2, 2, white)
	screen:fillRect(x2, y2, 2, 2, blue)
	screen:print(10,10, math.deg(aim), white)
	screen:flip()
end

[radioactive_X]

Thanks for the answer but using your method I get the same time (for offscreen) because of calling image:width() and height() a 100.000 times.
If I compare them to 0 I get a time of zero :)

So basically if i don't have a preset value to which to compare to it doesn't matter which method i use.

[Merick]

image:width() or height() are built-in functions and it takes longer to use a function than it takes to access the value of a variable, so try setting up an image table like this:

pic = {}
pic.image = Image.load(image)
pic.width = pic.image:width()
pic.height = pic.image:height()

[radioactive_X]

Yea, I read that discussion.

Thank you all for your help. :)

[Urameshi]

your welcome:)

[cruisx]

Umm how can i make it so that an image will come up adn ask the viewer to press start to start the program? also would it be possiable to play some sound whil the "press start to confirm image is up"

--Load images into a table
Images = {
    Image.load("images/cycle.jpg"),
    Image.load("images/background.jpg"),
    Image.load("images/epic.png"),
    Image.load("images/test2.jpg"),
    Image.load("images/work2.jpg"),
    Image.load("images/need.jpg"),
    
}

currentImageToDisplay = 1;  

while true do
    screen:clear()
    pad = Controls.read()
    
    if pad:r() and pad ~= oldpad and currentImageToDisplay < table.getn(Images) then
        currentImageToDisplay = currentImageToDisplay + 1;
    end
    
    if pad:l() and pad ~= oldpad and currentImageToDisplay > 1 then
        currentImageToDisplay = currentImageToDisplay - 1;
    end

    screen:blit(0, 0, Images[currentImageToDisplay]);
    
    screen.waitVblankStart() 
    screen.flip()
    oldpad = pad
end

[emericaska8r]

make another loop before the one you have for your program. make it display the picture, or text asking the user to press x. in the loop just have

while true do
screen:clear()
screen:blit(0,0,pressStartPic)
pad = Controls.read()
if pad:start() then
  break
end
screen.flip()
screen.waitVblankStart()
end

that way, if start is pressed, the current loop is broken, so your program will continue to the rest of your script below it. :tup:

For sound, yes it is possible. Just look at the lua wiki for sound functions.

[Urameshi]

your smilies not showin

[PSPJunkie_]

your smilies not showin

Good to know? ....

[emericaska8r]

yes i know, i disabled them in text since i posted code, and forgot.
there we go ^^

[Urameshi]

[KleptoOne]

what I'm saying is that if you had an image that was larger than the screen size, let's say 500x500, if you tried to blit it at -479 x -271 the image would be blitted and you would still be able to see the part of the image that's supposed to be in the visible screen area, but if you went further than that, -500 x -500, the image will not be blitted.

even if it doesn't show the image, it does take a small amount time for the lua player do it's internal checks on the image, so yes you should use a check to see if the image will be shown.

if x >= -image:width() and -image:width() > -480 then
         screen:blit(x,y,image)
end

----

In this code, can anyone tell me why my angle is off by 90 degrees?

function degree() return math.rad(math.abs(math.deg(math.atan2(pad:analogX(),pad:analogY()))-180)) end
function newx(x, radius, radian) return (x + math.cos(radian)*radius) end
function newy(y, radius, radian) return (y + math.sin(radian)*radius) end

white = Color.new(255,255,255)
blue  = Color.new(0,0,255)
red   = Color.new(255,0,0)

aim = -1
pad = Controls.read()

x = 240
y = 136
x2 = x
y2 = y

while not pad:square() do

	pad = Controls.read()
	if math.abs(pad:analogX()) > 25 or math.abs(pad:analogY()) > 25 then
		aim = degree()
	end
	
	if aim ~= -1 then
		x2 = newx(x, 20, aim)
		y2 = newy(y, 20, aim)
	end

	screen:clear()
	screen:drawLine(x, y, x2, y2, red)
	screen:fillRect(x, y, 2, 2, white)
	screen:fillRect(x2, y2, 2, 2, blue)
	screen:print(10,10, math.deg(aim), white)
	screen:flip()
end

I've used these algorithms in my car racing demo when playing around with the gu, and I got the same 90 offset. I could never figure it out so if anyone is really good with trig maybe they can, but I fixed it by subtracting 90 from my angle before calculating the new coordinate.

[psp phd]

Could anyone tell me what this error means?

"libpng error: Too many IDAT's found"

I thought it meant, there was too many .png files in the folder, but I erased 5 of them & still get the same error...


EDIT: answered my own question... the .png file I was trying to load was too big. It seems to load fine, now that I lowered the size too under 100 kb. :)

[SG57]

IDAT = image data chunk. IDAT contains all of the image's compressed pixel data. Single IDATs are perfectly fine as long as they contain no more than 2 gb's (i believe its 2) of compressed data, in most images the compressed data is split into several IDAT chunks. This means small IDAT chunks are the most common, particularly in sizes of 8 or 32 kb. The image your trying to load has too many of these IDATs, most likely because your image exporter (photoshop?) compressed it too much for libpng for the PSP to handle the IDATs (?). My advice is to open the PNG in MSPaint (if it doesnt have transparency) and save it as PNG again, but if it does have transparency, use GIMP or someother image editing software to export it as PNG again, at less of a compression.
-= Double Post =-

make another loop before the one you have for your program. make it display the picture, or text asking the user to press x. in the loop just have

while true do
screen:clear()
screen:blit(0,0,pressStartPic)
pad = Controls.read()
if pad:start() then
  break
end
screen.flip()
screen.waitVblankStart()
end

that way, if start is pressed, the current loop is broken, so your program will continue to the rest of your script below it.

For sound, yes it is possible. Just look at the lua wiki for sound functions.

Thought id comment on this too, as Its not too far back...

Creating multiple infinite loops disrupts a programs 'flow'. You should use a state system to not only have a constant flow, but be able to go back and forth between game states more easily then restarting the script or something.

ex

GameStates = { Intro = 0, Menu = 1, Game = 2 }

g_State = GameStates.Intro

oldpad = Controls.read()

white = Color.new(255,255,255)

while true do
     pad = Controls.read()

     if g_State == GameStates.Intro then
          screen:clear()
          screen:print(0,0,"Game States Example - This is the intro",white)

          if pad:cross() and pad ~= oldpad then
               g_State = GameStates.Menu
          end
     elseif g_State == GameStates.Menu then
          screen:print(0,0,"Main Menu",white)
          screen:print(0,10,"Press X to start game",white)
          screen:print(0,20,"Press O to go back to intro",white)

          if pad:cross() and pad ~= oldpad then
                g_State = GameStates.Game
          elseif pad:circle() and pad ~= oldpad then
                g_State = GameStates.Intro
          end
     elseif g_State == GameStates.Game then
          screen:print(0,0,"Game",white)
          screen:print(0,10,"Press X to go back to main menu",white)

          if pad:cross() and pad ~= oldpad then
                g_State = GameStates.Menu
          end
     end

     oldpad = pad
     screen.waitVblankStart()
     screen.flip()
end

I believe my syntax is correct there...

[emericaska8r]

yea, thats a good idea. thanks sg :)

[Bob Hoil]

Hey guys i have my collision code coded and everything i just have one question.

Spoiler for CODE:

background=Image.load("im ages/menu.png")
fb=Image.load("images/fb.png")
fbclicked=Image.load("ima ges/fbclicked.png")
apps=Image.load("images/apps.png")
appsclicked=Image.load("i mages/appsclicked.png")
wb=Image.load("images/wb.png")
wbclicked=Image.load("ima ges/wbclicked.png")
games=Image.load("images/games.png")
gamesclicked=Image.load(" images/gamesclicked.png")
mp=Image.load("images/mp.png")
mpclicked=Image.load("ima ges/mpclicked.png")
white=Color.new(255,250,2 50)
cursor = Image.load("images/cursor.png")

sensitivity = 40
maxspeed = 3

Cursor = {x = 30, y = 100, w = 32, h = 32, oldx = 200, oldy = 50, img = Image.load("images/cursor.png"), s = 4}

buttonimg = Image.load("images/fb.png")
button={}
button[1] = {x = 21, y = 234, h = buttonimg:height(), w = buttonimg:width()}

function moveCursor()
pad=Controls.read()
if pad:analogX() < -sensitivity or pad:analogX() > sensitivity then
Cursor.x = Cursor.x + pad:analogX()/(128/maxspeed)
end
if pad:analogY() < -sensitivity or pad:analogY() > sensitivity then
Cursor.y = Cursor.y + pad:analogY()/(128/maxspeed)
end
end

function clock()
time = os.time()
timestring = os.date("%c",time)
timeinfo = os.date("*t", time)
hour = timeinfo.hour
if hour > 11 then ampm = "PM"
elseif hour < 12 then ampm = "AM"
end
min = timeinfo.min
if min < 10 then
min = "0" .. min
end
hour = timeinfo.hour
if hour > 12 then
hour = hour - 12
end
screenrint(325, 26,hour..":" ..min .. " "..ampm, white)
end

function collision(ob1,ob2)
return (ob1.x + ob1.w > ob2.x) and (ob1.x < ob2.x + ob2.w) and (ob1.y + ob1.h > ob2.y) and (ob1.y < ob2.y + ob2.h)
end

function screenPrint()
screen:blit(0,0,backgroun d)
screen:blit(21,234,fb)
screen:blit(113,234,mp)
screen:blit(210,234,apps)
screen:blit(305,234,games )
screen:blit(399,234,wb)
screen:blit(Cursor.x,Curs or.y,Cursor.img)
screenrint(424,26, System.powerGetBatteryLif ePercent(),white)
end

while true do
screen:clear()

moveCursor()

screenPrint()

clock()

screen.waitVblankStart()
screen.flip()
end

That is my code. What i want to know is how to integrate it so that when my cursor goes over the button it will change the image and then if i hit x on it it will dofile("fb.lua").

Thanks To anyone that helps

Bob Hoil

[TacticalPenguin]

if pad:cross() and collision(something,somet hing) then dofile("fb.lua") end

[KleptoOne]

Your code tweaking Hoil, I think it would be good if you wrote this function yourself. A simple loop and a slight modification to your button table is all you need. Put up some code and we can walk you through any logic errors you might run into, but you're never going to learn be asking for ready made code.

My opinion, if someone wants to give and not teach, then by all means. But I think we as a community should support teaching concepts. Give a man a fish and he'll eat for a day, teach a man to fish and he'll eat for life. (as long as there are fish to eat)

[PSPJunkie_]

Your code tweaking Hoil, I think it would be good if you wrote this function yourself. A simple loop and a slight modification to your button table is all you need. Put up some code and we can walk you through any logic errors you might run into, but you're never going to learn be asking for ready made code.

My opinion, if someone wants to give and not teach, then by all means. But I think we as a community should support teaching concepts. Give a man a fish and he'll eat for a day, teach a man to fish and he'll eat for life. (as long as there are fish to eat)

Very true. Don't you ever, ever go to evilmana.

[TacticalPenguin]

Lol evilmana ftl.

[KleptoOne]

Nah, I'm a person of habit, I have my favorites and cycle through them. Some may even consider it borderline OCD, heh. Maybe someday.

[TacticalPenguin]

Ocd?