title: Processing: transparent image over curves
body: <p>Im new to Processing. I would like to put a .jpg or .png over curves and ellipses, so that they can see only where the image is transparent. 
  My code is below. The problem with it is that the transparent area is not fully transparent, but transparent white and the not-transparent parts have also decreased opacity. </p>
  
  <pre><code>    PImage img;
  
      void setup() {
        size(300,500);
        frameRate(30); 
        strokeWeight(4);   
        img = loadImage("sziluettmeret.jpg"); 
      }
  
     void draw() {
          background(0, 50, 70);  
          stroke(0,70,90);
          noFill();
          beginShape();
          curveVertex(-100,  -100);
          curveVertex(10, 10);
          curveVertex(250,  250);
          curveVertex(300,  300);
          endShape();
  
         fill(255);
         ellipse(20 ,20,15,15);
  
         noFill();
         tint(255, 100);
         image(img, 0, 0);
      }
  </code></pre>
  
  <hr>
  
  <p>UPDATE:</p>
  
  <p>I have this in my code:</p>
  
  <pre><code>    loadPixels();
      for(int i=0; i &lt; img.pixels.length; i++) {
      tmpColor = img.pixels[i];
      tmpRed = red(tmpColor);
      tmpGreen = blue(tmpColor);
      tmpBlue = green(tmpColor);
      tmpAlpha = 255 - ((tmpRed + tmpGreen + tmpBlue)/3);
      img.pixels[i] = color(2*tmpRed,tmpGreen/2,tmpBlue,0); 
      if(0xFFFFFF == tmpColor)
  
  
        }
       updatePixels();
  </code></pre>
  
  <p>The picture does not become transparent. (But it becomes purple, so the loop runs on every pixel for sure)</p>