Where is this stroke coming from?

Processing Coding Questions
1

I get a strange grey stroke when drawing, where is it coming from?

22

PGraphics pg;


void setup() {
  size(800, 600, P2D);
  pg = createGraphics(width, height, P2D);
  pg.beginDraw();
  pg.background(255);
  pg.endDraw();
}


void draw() {
  image(pg, 0, 0);  
}


void mouseDragged() {
 pg.beginDraw();
 pg.noStroke();
 pg.fill(255);
 pg.ellipse(mouseX, mouseY, 50, 50);
 pg.endDraw();
}
2

try

  noSmooth();
2 Likes
3

Hello,

Added background():

void mouseDragged()
{
 pg.beginDraw();
 pg.background(255);
 pg.noStroke();
 //pg.stroke(100);
 //pg.strokeWeight(2);
 pg.fill(255);
 pg.ellipse(mouseX, mouseY, 50, 50);
 pg.endDraw();
}

References:
https://processing.org/examples/creategraphics.html
https://processing.org/reference/createGraphics_.html

:slight_smile:

4

Kll’s suggestion works, yet I’m still curious why the grey strokes are showing up. It seems pg.ellipse is causing it, since the strokes aren’t there when you swap it with pg.rect

1 Like
5

Possibly your blendmode? You are antialiasing / smoothing an ellipse against a null background. Then you are copying the result onto a white background, but it looks like you are getting pixels that are pre-blended onto the null-as-black, resulting in gray. Just a quick guess.

Possibly the difference is that pg.rect doesn’t antialias when aligned to pixel units.

1 Like
6

It is there with the rectangle rotated.

Without pg.background(255) :
image

With pg.background():
image

Code used (modified original):

PGraphics pg;
boolean pgReady = false;

void setup() 
  {
  size(400, 400, P2D);
  //noSmooth();
  pg = createGraphics(width, height, P2D);
  //pg.beginDraw();
  //pg.background(255);
  //pg.endDraw();
  }

void draw() 
  {
  background(255);
  if (pgReady) 
    image(pg, 0, 0);
  }

void mouseDragged()
  {
  pgReady = true;
  pg.beginDraw();
  pg.background(255);
  pg.noStroke();
  pg.fill(250);
  pg.rotate(TAU/100);
  pg.rect(50, 50, 150, 150);
  pg.ellipse(mouseX, mouseY, 50, 50);
  pg.endDraw();
  }

noSmooth() was not required in my example and will not give smooth() shapes if they are coded to be visible.

:slight_smile:

3 Likes