Paint program

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iPoisonxL
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Paint program

Post by iPoisonxL »

Hi. I'm trying to create a paint program, and it's working well. The only current problem is that it draws over the same pixel, over, and over again if you hold down the mouse button. Therefore creating thousands of pixels, and huge lag. I'm trying to find my way around this, and since I use a table that has all the pixel positions I thought maybe I should create a function that loops through the table and detects if anything repeats? Can't seem to do it. Here's the code.

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table.has = function(tabl, value)
	for i,v in pairs(tabl) do
		if value == item then return true end
	end
	return false
end

table.length = function(tabl)
	local count = 0
	for i,v in pairs(tabl) do
		count = count + 1
	end
	return count
end

function love.load()
	pixels = {}
end

function love.update()
	pos = {love.mouse.getX(), love.mouse.getY()}
	if(love.mouse.isDown("r"))then
		pixels = {}
	end
	
	for i,v in ipairs(pixels) do
		if(table.has(pixels, v))then
			v = nil
		end
	end
	
	if(love.mouse.isDown("l"))then
		table.insert(pixels, pos)
	end
end

function love.draw()
	love.graphics.setColor(255,255,255)
	for i,v in ipairs(pixels) do
		love.graphics.point(v[1], v[2])
	end
	love.graphics.print(love.timer.getFPS(), 10, 10)
	love.graphics.print("Amount of pixels being drawn: "..table.length(pixels), 10, 30)
end
and here's the .love
main.love
(481 Bytes) Downloaded 294 times

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miko
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Location: PL

Re: Paint program

Post by miko »

iPoisonxL wrote: Hi. I'm trying to create a paint program, and it's working well.
If you were using canvases, it would work even better - attached:
main-canvas.love
(594 Bytes) Downloaded 367 times
My lovely code lives at GitHub: http://github.com/miko/Love2d-samples
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micha
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Re: Paint program

Post by micha »

It seem rather strange to me that you are storing the image in a table as a set of coordinates. The natural approach for me is having a table of tables (a 2d-array) of a fixed size and inserting the color of each pixel there.
If you want to save memory you can still assign nil to all empty pixels.

To make the difference clear: Your approach has a table that contains coordinates like this:

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{{x1,y1},{x2,y2},...}
The more natural approach has one 2d array of colors:

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{{c1,c2,c3,...},{c100,c101,...},...}
Drawing a pixel is changing a value inside the array instead of adding a new entry to the array.
As miko says, drawing this might be faster if you use a canvas (or imageData).
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iPoisonxL
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Re: Paint program

Post by iPoisonxL »

I can't use canvases, since my OpenGL implementation doesn't support it. I have quite an old computer. Isn't there a way to delete duplicates in tables?

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Ref
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Re: Paint program

Post by Ref »

Obvious, just a programming exercise - of limited value.
At best, script just not fast enough to keep up with mouse movements.
You can extend the useful number of pixels with reasonable frame rate by optimizing your code.
( Might want to limit mouse movement to screen to avoid creating points that can't be displayed. )
Canvases will permit continuous point addition without effecting frame rate but you have to remember to invert the y axes.

Edit1: Don't add duplicates to the table in the first place.
Edit2: Could improve response time by modifying love.run - only redraw screen if pixel added. Doesn't really address real problem - mouse moving too fast.
Attachments
pixelPaintCanvas.love
Drawing a canvas
(425 Bytes) Downloaded 250 times
pixelPaintTable.love
Drawing from a point table
(550 Bytes) Downloaded 233 times
Last edited by Ref on Tue Oct 22, 2013 4:33 pm, edited 2 times in total.
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T-Bone
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Re: Paint program

Post by T-Bone »

Even without Canvases, using ImageData and setPixel might work depending on how you implement it.
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iPoisonxL
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Re: Paint program

Post by iPoisonxL »

I'm currently trying to make a 2D Array that has every pixel in it, but I can't figure out how. I won't do it manually, because you know, 480K values is a lot.

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Ref
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Re: Paint program

Post by Ref »

Just for completeness - added drawing to image data.
Converting imageData to an image limits frame rate.
Attachments
pixelDrawImageData.love
Drawing to imageData
(477 Bytes) Downloaded 235 times
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micha
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Re: Paint program

Post by micha »

iPoisonxL wrote:I'm currently trying to make a 2D Array that has every pixel in it, but I can't figure out how. I won't do it manually, because you know, 480K values is a lot.
After thinking about it for a while, probably ImageData is the best way to go. For completeness, here is how to do the 2d-array:

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for i = 1,width do
  pixel[i] = {}
  for j = 1,height do
    pixel[i][j] = 0
  end
end
Here you can save some memory by only assigning those pixels that are non-black (or whatever color the background is). Only create the tables for each column:

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for i = 1,width do
  pixel[i] = {}
end
And then insert the values, whenever needed:

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function someMouseClickEvent(x,y)
  pixel[x][y] = color
end
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iPoisonxL
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Re: Paint program

Post by iPoisonxL »

micha wrote:

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for i = 1,width do
  pixel[i] = {}
  for j = 1,height do
    pixel[i][j] = 0
  end
end
could you explain this snippet to me? I'm not big on 2D arrays, haven't really been interested in them. I now realize how important they can be.

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