How can I get lines to draw only on black?

Krashan

PFont f;

void setup() {
  background(255);
  size(700, 700);
  f=createFont("HelveticaLTStd-BoldCond.otf", 300);
  smooth();
  fill(0);
  textFont(f);
  text("D", 270, 400);
}

void draw() {
  stroke(random(255), random(255), random(255), random(255));
  line(290, random(180, 400), random(350, 430), random(180, 400));
  if (mousePressed) {
    stop();
  }
}

This is the code to the application, I'm drawing a letter D and i want to draw lines above it but only on the letter itself, not on the white inside and outside of it. Is there any way I can do this?

Lord_of_the_Galaxy

At pixel level, probably. Otherwise, probably not. Unless,the line is of the same color as the background, which is not the case.

Chrisir

sure there is a way

Krashan

and what is that @Chrisir ?

jeremydouglass

@Krashan --

The concept you are looking for is a mask. In Processing, this is implemented through PImage.mask().

https://processing.org/reference/PImage_mask_.html

1. draw lines in a PGraphics image
2. draw text in another PGraphics.
3. apply the text as a mask() to the lines, creating an image of lines "cut out" in the shape of the text.
4. draw that image with image().

kfrajer

Maybe there is a better way (Edited ** I am referring to my post). Here is my attempt:

Kf

PFont f;
PGraphics pg;
PGraphics amask;

PGraphics lines;

void setup() {
  background(255);
  size(700, 700);
  f=createFont("Arial", 300);
  smooth();
  fill(0);
  textFont(f);

  pg = createGraphics(width, height);
  pg.beginDraw();
  //pg.background(255);
  pg.fill(0);
  pg.textFont(f);
  pg.text("D", 270, 400);
  pg.endDraw();

  amask = createGraphics(width, height);
  amask.beginDraw();
  amask.background(255);
  amask.fill(0);
  amask.textFont(f);
  amask.text("D", 270, 400);
  amask.endDraw();
  amask.filter(INVERT);

  lines = createGraphics(width, height);
}

void draw() {

  lines.beginDraw();
  lines.stroke(random(255), random(255), random(255), random(255));
  lines.line(290, random(180, 400), random(350, 430), random(180, 400));
  lines.endDraw();
  lines.mask(amask);

  image(pg, 0, 0);
  image(lines,0,0);
  pg.copy(0,0,width,height,0,0,width,height);

  if (mousePressed) {
    stop();
  }
}

Lord_of_the_Galaxy

I did not know that, thanks for the answer.

Krashan

Thank you so much!