My own DrawEllipse function - GameCreators Forum

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Hubert BAYRE

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Posted: 5th Jan 2018 11:28 Edited at: 5th Jan 2018 11:29

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Hello !

I'm searching some examples to code my own draw FILLED ellipse function.
In fact i need this to draw filled circles on my renderimage.

Have you some code sample to do this ?

this is for an unfilled circle :

+ Code Snippet

Function Dessin_tracer_circle( StartX AS INTEGER , StartY AS INTEGER, Rayon as Integer, Couleur)

	Local Angle as Integer
	Local x as integer
	Local y as integer
	
    For Angle = 0 to 360 
        x = StartX + Cos(Angle) * Rayon
        y = StartY + Sin(Angle) * Rayon
        DrawLine (x,y,x,y,Couleur, Couleur)
    Next

EndFunction

Some informations here, but i dont know how to do this with agk (https://stackoverflow.com/questions/10322341/simple-algorithm-for-drawing-filled-ellipse-in-c-c)

Many thanks !

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MikeHart

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Posted: 5th Jan 2018 11:48

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How about using this command?

DrawEllipse( x, y, radiusx, radiusy, color1, color2, filled )

Running Windows 7 Home, 64 bit, 8 GB ram, Athlon II X2 255, ATI Radeon HD 4200. Using AGK2 Tier 1.

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Bengismo

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Posted: 5th Jan 2018 12:15 Edited at: 5th Jan 2018 12:17

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Why not use the built in function??

DrawEllipse( x, y, radiusx, radiusy, color1, color2, filled )
https://www.appgamekit.com/documentation/Reference/Core/DrawEllipse.htm

Oops...mike beat me to it.... lol

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puzzler2018

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Posted: 5th Jan 2018 12:53

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aww bless and Hubert took the time and energy to create own one.

It is all about learning from each other,so all good all round anyway

Good coding though Hubert

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Hubert BAYRE

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Posted: 5th Jan 2018 21:06 Edited at: 5th Jan 2018 21:06

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I'm searching a way to fix my problem here (https://forum.thegamecreators.com/thread/221225).
Agk2 is very powerfull. I know the DrawEllipse function. But in my case i need to find how to finish my project.

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Hubert BAYRE

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Posted: 5th Jan 2018 21:21 Edited at: 5th Jan 2018 21:28

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http://enchantia.com/graphapp/doc/tech/ellipses.html
Interesting an ellipse filled using scan lines. Not sure to do this with Agk2 :

extern void row(int x, int y, unsigned int width);

#define incx() x++, dxt += d2xt, t += dxt
	#define incy() y--, dyt += d2yt, t += dyt

void fill_ellipse_1(int xc, int yc, int a, int b)
	{			/* e(x,y) = b^2*x^2 + a^2*y^2 - a^2*b^2 */
		int x = 0, y = b;
		unsigned int width = 1;
		long a2 = (long)a*a, b2 = (long)b*b;
		long crit1 = -(a2/4 + a%2 + b2);
		long crit2 = -(b2/4 + b%2 + a2);
		long crit3 = -(b2/4 + b%2);
		long t = -a2*y; /* e(x+1/2,y-1/2) - (a^2+b^2)/4 */
		long dxt = 2*b2*x, dyt = -2*a2*y;
		long d2xt = 2*b2, d2yt = 2*a2;

while (y>=0 && x<=a) {
			if (t + b2*x <= crit1 ||     /* e(x+1,y-1/2) <= 0 */
			    t + a2*y <= crit3) {     /* e(x+1/2,y) <= 0 */
				incx();
				width += 2;
			}
			else if (t - a2*y > crit2) { /* e(x+1/2,y-1) > 0 */
				row(xc-x, yc-y, width);
				if (y!=0)
					row(xc-x, yc+y, width);
				incy();
			}
			else {
				row(xc-x, yc-y, width);
				if (y!=0)
					row(xc-x, yc+y, width);
				incx();
				incy();
				width += 2;
			}
		}
		if (b == 0)
			row(xc-a, yc, 2*a+1);
	}

+ Code Snippet

	extern void row(int x, int y, unsigned int width);

	#define incx() x++, dxt += d2xt, t += dxt
	#define incy() y--, dyt += d2yt, t += dyt

	void fill_ellipse_1(int xc, int yc, int a, int b)
	{			/* e(x,y) = b^2*x^2 + a^2*y^2 - a^2*b^2 */
		int x = 0, y = b;
		unsigned int width = 1;
		long a2 = (long)a*a, b2 = (long)b*b;
		long crit1 = -(a2/4 + a%2 + b2);
		long crit2 = -(b2/4 + b%2 + a2);
		long crit3 = -(b2/4 + b%2);
		long t = -a2*y; /* e(x+1/2,y-1/2) - (a^2+b^2)/4 */
		long dxt = 2*b2*x, dyt = -2*a2*y;
		long d2xt = 2*b2, d2yt = 2*a2;

		while (y>=0 && x<=a) {
			if (t + b2*x <= crit1 ||     /* e(x+1,y-1/2) <= 0 */
			    t + a2*y <= crit3) {     /* e(x+1/2,y) <= 0 */
				incx();
				width += 2;
			}
			else if (t - a2*y > crit2) { /* e(x+1/2,y-1) > 0 */
				row(xc-x, yc-y, width);
				if (y!=0)
					row(xc-x, yc+y, width);
				incy();
			}
			else {
				row(xc-x, yc-y, width);
				if (y!=0)
					row(xc-x, yc+y, width);
				incx();
				incy();
				width += 2;
			}
		}
		if (b == 0)
			row(xc-a, yc, 2*a+1);
	}

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puzzler2018

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Posted: 5th Jan 2018 22:18

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Nice interesting idea for something different

Will have a go at converting that code to agk when got some time this weekend for you

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Hubert BAYRE

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Posted: 5th Jan 2018 22:33 Edited at: 5th Jan 2018 22:37

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Translated to agk :

Function Row (x as Integer, y as Integer, width as Integer)
	
	Local Color as Integer
	
	Color = MakeColor (255,255,255)
	DrawLine (x,y,x + width, y,Color, Color)
	
EndFunction
 
Function fill_ellipse_1(xc as Integer, yc as Integer, a as Integer, b as Integer)

/* e(x,y) = b^2*x^2 + a^2*y^2 - a^2*b^2 */
    
    Local x as Integer
    Local y as Integer
    Local width as Integer
    
    Local a2 as Integer
    Local b2 as Integer

Local crit1 as Integer
	Local crit2 as Integer
	Local crit3 as Integer
	Local t as Integer
	
	Local dxt as Integer
	Local dyt as Integer

Local d2xt as Integer
	Local d2yt as Integer
	
    x = 0
    y = b
    width = 1
    
    a2 = a * a
    b2 = b * b 
      
    crit1 = -(a2/4 + mod(a,2) + b2)
    crit2 = -(b2/4 + mod(b,2) + a2)
    crit3 = -(b2/4 + mod (b,2))
        
    t = -a2 * y /* e(x+1/2,y-1/2) - (a^2+b^2)/4 */
    
    dxt  = 2 * b2 * x
    dyt  = -2 * a2 * y
    d2xt = 2 * b2
    d2yt = 2 * a2
 
    While y>=0 and x <= a
        
        If t + b2 * x <= crit1 or t + a2 * y <= crit3     /* e(x+1,y-1/2) <= 0 */  /* e(x+1/2,y) <= 0 */
            
            //Incx()
			x = x + 1
			dxt = dxt + d2xt
			t = t + dxt
            
            width = width + 2

ElseIf t - a2*y > crit2  /* e(x+1/2,y-1) > 0 */
				row(xc-x, yc-y, width)
				If (y <> 0) Then row(xc-x, yc+y, width)
				
				//Incy()
				y = y - 1
				dyt = dyt + d2yt
				t = t + dyt
				
        Else 
        
            row(xc - x, yc - y, width)

If (y <> 0) Then row(xc - x, yc + y, width)

// IncX
			x = x + 1
			dxt = dxt + d2xt
			t = t + dxt

//Incy()
			y = y - 1
			dyt = dyt + d2yt
			t = t + dyt

width = width + 2

EndIf
        
    EndWhile

If b = 0 Then Row(xc - a, yc, 2 * a + 1)

EndFunction

+ Code Snippet

Function Row (x as Integer, y as Integer, width as Integer)
	
	Local Color as Integer
	
	Color = MakeColor (255,255,255)
	DrawLine (x,y,x + width, y,Color, Color)
	
EndFunction
 
Function fill_ellipse_1(xc as Integer, yc as Integer, a as Integer, b as Integer)

    /* e(x,y) = b^2*x^2 + a^2*y^2 - a^2*b^2 */
    
    Local x as Integer
    Local y as Integer
    Local width as Integer
    
    Local a2 as Integer
    Local b2 as Integer

	Local crit1 as Integer
	Local crit2 as Integer
	Local crit3 as Integer
	Local t as Integer
	
	Local dxt as Integer
	Local dyt as Integer

	Local d2xt as Integer
	Local d2yt as Integer
	
    x = 0
    y = b
    width = 1
    
    a2 = a * a
    b2 = b * b 
      
    crit1 = -(a2/4 + mod(a,2) + b2)
    crit2 = -(b2/4 + mod(b,2) + a2)
    crit3 = -(b2/4 + mod (b,2))
        
    t = -a2 * y /* e(x+1/2,y-1/2) - (a^2+b^2)/4 */
    
    dxt  = 2 * b2 * x
    dyt  = -2 * a2 * y
    d2xt = 2 * b2
    d2yt = 2 * a2
 
    While y>=0 and x <= a
        
        If t + b2 * x <= crit1 or t + a2 * y <= crit3     /* e(x+1,y-1/2) <= 0 */  /* e(x+1/2,y) <= 0 */
            
            //Incx()
			x = x + 1
			dxt = dxt + d2xt
			t = t + dxt
            
            width = width + 2

        ElseIf t - a2*y > crit2  /* e(x+1/2,y-1) > 0 */
				row(xc-x, yc-y, width)
				If (y <> 0) Then row(xc-x, yc+y, width)
				
				//Incy()
				y = y - 1
				dyt = dyt + d2yt
				t = t + dyt
				
        Else 
        
            row(xc - x, yc - y, width)

            If (y <> 0) Then row(xc - x, yc + y, width)

			// IncX
			x = x + 1
			dxt = dxt + d2xt
			t = t + dxt

            //Incy()
			y = y - 1
			dyt = dyt + d2yt
			t = t + dyt

            width = width + 2

        EndIf
        
    EndWhile

    If b = 0 Then Row(xc - a, yc, 2 * a + 1)

EndFunction

works fine.

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Hubert BAYRE

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Posted: 5th Jan 2018 22:52

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Version without external function :

Function fill_ellipse_1(xc as Integer, yc as Integer, a as Integer, b as Integer, Color as Integer)

/* e(x,y) = b^2*x^2 + a^2*y^2 - a^2*b^2 */
    
    Local x as Integer
    Local y as Integer
    Local width as Integer
    
    Local a2 as Integer
    Local b2 as Integer

Local crit1 as Integer
	Local crit2 as Integer
	Local crit3 as Integer
	Local t as Integer
	
	Local dxt as Integer
	Local dyt as Integer

Local d2xt as Integer
	Local d2yt as Integer
	
    x = 0
    y = b
    width = 1
    
    a2 = a * a
    b2 = b * b 
      
    crit1 = -(a2/4 + mod(a,2) + b2)
    crit2 = -(b2/4 + mod(b,2) + a2)
    crit3 = -(b2/4 + mod (b,2))
        
    t = -a2 * y /* e(x+1/2,y-1/2) - (a^2+b^2)/4 */
    
    dxt  = 2 * b2 * x
    dyt  = -2 * a2 * y
    d2xt = 2 * b2
    d2yt = 2 * a2
 
    While y>=0 and x <= a
        
        If t + b2 * x <= crit1 or t + a2 * y <= crit3     /* e(x+1,y-1/2) <= 0 */  /* e(x+1/2,y) <= 0 */
            
            //Incx()
			x = x + 1
			dxt = dxt + d2xt
			t = t + dxt
            
            width = width + 2

ElseIf t - a2*y > crit2  /* e(x+1/2,y-1) > 0 */
			
				DrawLine (xc-x, yc-y,xc-x + width, yc-y,Color, Color)
			
				If (y <> 0) Then DrawLine(xc-x, yc+y, xc-x+ width, yc+y, Color, Color)
				
				//Incy()
				y = y - 1
				dyt = dyt + d2yt
				t = t + dyt
				
        Else 
        
            DrawLine (xc - x, yc - y, xc - x+ width, yc - y, Color, Color)

If (y <> 0) Then DrawLine(xc - x, yc + y, xc - x + width, yc + y, Color, Color)

// IncX
			x = x + 1
			dxt = dxt + d2xt
			t = t + dxt

//Incy()
			y = y - 1
			dyt = dyt + d2yt
			t = t + dyt

width = width + 2

EndIf
        
    EndWhile

If b = 0 Then DrawLine (xc - a, yc, xc - a + 2 * a + 1, yc, Color, Color)

EndFunction

+ Code Snippet

Function fill_ellipse_1(xc as Integer, yc as Integer, a as Integer, b as Integer, Color as Integer)

    /* e(x,y) = b^2*x^2 + a^2*y^2 - a^2*b^2 */
    
    Local x as Integer
    Local y as Integer
    Local width as Integer
    
    Local a2 as Integer
    Local b2 as Integer

	Local crit1 as Integer
	Local crit2 as Integer
	Local crit3 as Integer
	Local t as Integer
	
	Local dxt as Integer
	Local dyt as Integer

	Local d2xt as Integer
	Local d2yt as Integer
	
    x = 0
    y = b
    width = 1
    
    a2 = a * a
    b2 = b * b 
      
    crit1 = -(a2/4 + mod(a,2) + b2)
    crit2 = -(b2/4 + mod(b,2) + a2)
    crit3 = -(b2/4 + mod (b,2))
        
    t = -a2 * y /* e(x+1/2,y-1/2) - (a^2+b^2)/4 */
    
    dxt  = 2 * b2 * x
    dyt  = -2 * a2 * y
    d2xt = 2 * b2
    d2yt = 2 * a2
 
    While y>=0 and x <= a
        
        If t + b2 * x <= crit1 or t + a2 * y <= crit3     /* e(x+1,y-1/2) <= 0 */  /* e(x+1/2,y) <= 0 */
            
            //Incx()
			x = x + 1
			dxt = dxt + d2xt
			t = t + dxt
            
            width = width + 2

        ElseIf t - a2*y > crit2  /* e(x+1/2,y-1) > 0 */
			
				DrawLine (xc-x, yc-y,xc-x + width, yc-y,Color, Color)
			
				If (y <> 0) Then DrawLine(xc-x, yc+y, xc-x+ width, yc+y, Color, Color)
				
				//Incy()
				y = y - 1
				dyt = dyt + d2yt
				t = t + dyt
				
        Else 
        
            DrawLine (xc - x, yc - y, xc - x+ width, yc - y, Color, Color)

            If (y <> 0) Then DrawLine(xc - x, yc + y, xc - x + width, yc + y, Color, Color)

			// IncX
			x = x + 1
			dxt = dxt + d2xt
			t = t + dxt

            //Incy()
			y = y - 1
			dyt = dyt + d2yt
			t = t + dyt

            width = width + 2

        EndIf
        
    EndWhile

    If b = 0 Then DrawLine (xc - a, yc, xc - a + 2 * a + 1, yc, Color, Color)

EndFunction

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puzzler2018

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Posted: 5th Jan 2018 23:17

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It does indeed, awesome work my good fellow

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Hubert BAYRE

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Posted: 5th Jan 2018 23:19

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No anti-alias with this code, but my problem is fixed now. No idea where was finally the bug. This was the last challenge for my project. Now i've a cool project almost finished.
Many thanks at the community for the help.

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puzzler2018

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Posted: 5th Jan 2018 23:26

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you could still have used the in built version of drawellipse

but then if your project (maybe uni project requires you to make an ellipse proramatically) then good for you

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puzzler2018

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Posted: 5th Jan 2018 23:44 Edited at: 5th Jan 2018 23:45

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Are you going to be our man to be able to fill in any shape no matter how the shape is?

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Phaelax

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Posted: 8th Jan 2018 18:01

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Quote: "Are you going to be our man to be able to fill in any shape no matter how the shape is?"

Several of us have already done that, it's called a flood fill. Though with something as simple as an ellipse, it'd be overkill.

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janbo

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Posted: 9th Jan 2018 01:50 Edited at: 9th Jan 2018 04:41

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The Scan line method is much more efficient.
He could probably optimize it for his purposes, as I think he doesn't need to draw the full ellipse.
Not sure how he does it but...
I would draw with straight lines as it can happen that the pointer jumps leaving a gap in the resulting line.
Then you need a function that not only draws a circle, but a line with width.
Again I would "draw" the two halves of the circle outline, one a the line stat and one at the line end facing to the line opposite point and from there drawing lines connecting the two halves.
( ----------- )
Should be pretty fast and won't give you any gaps.

You can also fill every shape with the scanline method.
You need to split the polygon into convex shapes then each convex polygon into triangles, then every triangle into a top and bottom triangle with a horizontal edge and fill them with horizontal lines.
Not sure how efficient that is vs flood fill.

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Phaelax

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Posted: 10th Jan 2018 16:09

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If he's already got the math to draw the outline of the ellipse, then technically the ability to fill it is already there. Take an edge pixel and draw a horizontal line from it to the center. And the drawing loop can be minimized due to the fact an ellipse is made up of 4 identical quadrants, just reverse the Xs and Ys for each quadrant. (if that makes sense)

I typed this pseudo-code in notepad, so run it at your own risk. Not 100% sure it'll work, but I think it will if I did my math correctly. What this should do is start at the center of the ellipse and traverse along y-axis for the length of the ellipse's Y-radius. At each point, it'll calculate where the corresponding X-pixel should be for the outline of the ellipse. It will then drawn a line from that point horizontally to the other side of the ellipse. It'll do this for the top half and the bottom half (hence the two draw commands), as each line will handle drawing for two quadrants. (the first being the upper half, the second line draws the lower)

+ Code Snippet

(h,k) = center of ellipse
(a,b) = radii of ellipse on each axis



for y = 0 to ry-1
	//x = sqrt((((k+y)-k)^2 / b^2 - 1) * a^2) + h
	
	// simplified by using an origin of 0,0
	x = sqrt((1 - y^2/b^2) * a^2)

	drawLine( h-x, k-y, h+x, k-y)
	drawLine( h-x, k+y, h+x, k+y)

next y

In theory this should work for axis-aligned ellipses. If you want anti-aliased ellipses, I can probably manage it but I'll need to take time to do it and use more than notepad.

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