Search code examples
vectorprocessingpixel

Processing: Draw vector instead of pixels


I have a simple Processing Sketch, drawing a continuous line of ellipses with a 20px diameter. Is there a way to modify the sketch so that it draws vector shapes instead of pixels?

  void setup() {
  size(900, 900); 
  background(110, 255, 94);  

} 

void draw() {
  ellipse(mouseX, mouseY, 20, 20);
 fill(255);
}

Thanks to everyone who can provide some helpful advice.


Solution

  • Expanding my comment above, there a couple of things to tackle:

    1. drawing a continuous line of ellipses with a 20px diameter

    2. draws vector shapes

    Currently you're drawing ellipses based on mouse movement. A side effect is that if you move the mouse fast enough you will have gaps in between ellipses.

    To fill the gaps you can work out the distance between every two ellipses. If the distance is greater than the sizes of these two ellipses you can draw some in between.

    The PVector class provides a lerp() function that allows you easily interpolate between two points. You can read more on this and run some examples here

    Using the ratio between these distance of two points and the ellipse size the number of points needed in between. Here is an example that stores mouse locations to a list of PVectors as you drag the mouse:

    //create an array list to store points to draw
    ArrayList<PVector> path = new ArrayList<PVector>();
    //size of each ellipse
    float size = 20;
    //how tight will the extra ellipses be drawn together
    float tightness = 1.25;
    
    void setup() {
      size(900, 900);
    } 
    
    void draw() {
      background(110, 255, 94);
      fill(255);
    
      //for each point in the path, starting at 1 (not 0)
      for(int i = 1; i < path.size(); i++){
    
        //get a reference to the current and previous point
        PVector current  = path.get(i);
        PVector previous = path.get(i-1);
    
        //calculate the distance between them
        float distance = previous.dist(current);
    
        //work out how many points will need to be added in between the current and previous points to keep the path continuous (taking the ellipse size into account) 
        int extraPoints = (int)(round(distance/size * tightness));
    
        //draw the previous point
        ellipse(previous.x,previous.y,size,size);
    
        //if there are any exta points to be added, compute and draw them:
        for(int j = 0; j < extraPoints; j++){
    
          //work out a normalized (between 0.0 and 1.0) value of where each extra point should be
          //think of this as a percentage along a line: 0.0 = start of line, 0.5 = 50% along the line, 1.0 = end of the line
          float interpolation = map(j,0,extraPoints,0.0,1.0);
    
          //compute the point in between using PVector's linear interpolation (lerp()) functionality
          PVector inbetween = PVector.lerp(previous,current,interpolation);
    
          //draw the point in between
          ellipse(inbetween.x,inbetween.y,size,size);
        }
    
      }
    
      //draw instructions
      fill(0);
      text("SPACE = clear\nLEFT = decrease tightness\nRIGHT = increase tightness\ntightness:"+tightness,10,15);
    }
    
    void mouseDragged(){
      path.add(new PVector(mouseX,mouseY));
    }
    void keyPressed(){
      if(keyCode == LEFT)  tightness = constrain(tightness-0.1,0.0,3.0);
      if(keyCode == RIGHT) tightness = constrain(tightness+0.1,0.0,3.0);
      if(key == ' ') path.clear();
    }
    

    Note that the interpolation between points is linear. It's the simplest, but as the name implies, it's all about lines: it always connects two points in a straight line, not curves.

    I've added the option to control how tight interpolated ellipses will be packed together. Here are a couple of screenshots with different tightness levels. You'll notice as tightness increases, the lines will become more evident:

    tightness 0

    tightness 1.5

    tightness 3.0

    You run the code bellow:

    //create an array list to store points to draw
    var path = [];
    //size of each ellipse
    var ellipseSize = 20;
    //how tight will the extra ellipses be drawn together
    var tightness = 1.25;
    
    function setup() {
      createCanvas(900, 900);
    } 
    
    function draw() {
      background(110, 255, 94);
      fill(255);
      
      //for each point in the path, starting at 1 (not 0)
      for(var i = 1; i < path.length; i++){
        
        //get a reference to the current and previous point
        var current  = path[i];
        var previous = path[i-1];
        
        //calculate the distance between them
        var distance = previous.dist(current);
        
        //work out how many points will need to be added in between the current and previous points to keep the path continuous (taking the ellipse size into account) 
        var extraPoints = round(distance/ellipseSize * tightness);
        
        //draw the previous point
        ellipse(previous.x,previous.y,ellipseSize,ellipseSize);
        
        //if there are any exta points to be added, compute and draw them:
        for(var j = 0; j < extraPoints; j++){
          
          //work out a normalized (between 0.0 and 1.0) value of where each extra point should be
          //think of this as a percentage along a line: 0.0 = start of line, 0.5 = 50% along the line, 1.0 = end of the line
          var interpolation = map(j,0,extraPoints,0.0,1.0);
          
          //compute the point in between using PVector's linear interpolation (lerp()) functionality
          var inbetween = p5.Vector.lerp(previous,current,interpolation);
          
          //draw the point in between
          ellipse(inbetween.x,inbetween.y,ellipseSize,ellipseSize);
        }
        
      }
      
      //draw instructions
      fill(0);
      text("BACKSPACE = clear\n- = decrease tightness\n+ = increase tightness\ntightness:"+tightness,10,15);
    }
    
    function mouseDragged(){
      path.push(createVector(mouseX,mouseY));
    }
    function keyPressed(){
      if(keyCode == 189)  tightness = constrain(tightness-0.1,0.0,3.0);
      if(keyCode == 187) tightness = constrain(tightness+0.1,0.0,3.0);
      if(keyCode == BACKSPACE) path = [];
    }
    
    //https://stackoverflow.com/questions/40673192/processing-draw-vector-instead-of-pixels
    <script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.5.4/p5.min.js"></script>

    If you want smoother lines you will need to use a different interpolation such as quadratic or cubic interpolation. You can start with existing Processing functions for drawing curves such as curve() or bezier(),and you'll find some helpful resources unrelated to Processing here,here and here.

    On vector shapes

    You're not directly working with pixels[], you're drawing shapes. These shapes can easily be saved to PDF using Processing's PDF library Check out the Single Frame from an Animation (With Screen Display) example.

    Here is a version that saves to PDF when pressing the 's' key:

    import processing.pdf.*;
    
    //create an array list to store points to draw
    ArrayList<PVector> path = new ArrayList<PVector>();
    //size of each ellipse
    float size = 20;
    //how tight will the extra ellipses be drawn together
    float tightness = 1.25;
    
    //PDF saving
    boolean record;
    
    void setup() {
      size(900, 900);
    
    } 
    
    void draw() {
      background(110, 255, 94);
      fill(255);
    
      //if we need to save the current frame to pdf, begin recording drawing instructions
      if (record) {
        // Note that #### will be replaced with the frame number. Fancy!
        beginRecord(PDF, "frame-####.pdf"); 
      }
    
      //for each point in the path, starting at 1 (not 0)
      for(int i = 1; i < path.size(); i++){
    
        //get a reference to the current and previous point
        PVector current  = path.get(i);
        PVector previous = path.get(i-1);
    
        //calculate the distance between them
        float distance = previous.dist(current);
    
        //work out how many points will need to be added in between the current and previous points to keep the path continuous (taking the ellipse size into account) 
        int extraPoints = (int)(round(distance/size * tightness));
    
        //draw the previous point
        ellipse(previous.x,previous.y,size,size);
    
        //if there are any exta points to be added, compute and draw them:
        for(int j = 0; j < extraPoints; j++){
    
          //work out a normalized (between 0.0 and 1.0) value of where each extra point should be
          //think of this as a percentage along a line: 0.0 = start of line, 0.5 = 50% along the line, 1.0 = end of the line
          float interpolation = map(j,0,extraPoints,0.0,1.0);
    
          //compute the point in between using PVector's linear interpolation (lerp()) functionality
          PVector inbetween = PVector.lerp(previous,current,interpolation);
    
          //draw the point in between
          ellipse(inbetween.x,inbetween.y,size,size);
        }
    
      }
      //once what we want to save has been recorded to PDF, stop recording (this will skip saving the instructions text);
      if (record) {
        endRecord();
        record = false;
        println("pdf saved");
      }
    
      //draw instructions
      fill(0);
      text("SPACE = clear\nLEFT = decrease tightness\nRIGHT = increase tightness\ntightness:"+tightness+"\n's' = save PDF",10,15);
    }
    
    void mouseDragged(){
      path.add(new PVector(mouseX,mouseY));
    }
    void keyPressed(){
      if(keyCode == LEFT)  tightness = constrain(tightness-0.1,0.0,3.0);
      if(keyCode == RIGHT) tightness = constrain(tightness+0.1,0.0,3.0);
      if(key == ' ') path.clear();
      if(key == 's') record = true;
    }