# Does the mask-function behave differently from Processing to P5?

**URL:** <https://discourse.processing.org/t/does-the-mask-function-behave-differently-from-processing-to-p5/43357>\
**Category:** Coding Questions\
**Created:** [November 30, 2023, 3:01pm UTC](https://discourse.processing.org/t/does-the-mask-function-behave-differently-from-processing-to-p5/43357 "2023-11-30T15:01:00Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![glv](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/glv/32/18785_2.png) [@glv](https://discourse.processing.org/u/glv)\
**Post date:** [December 2, 2023, 9:23pm UTC](https://discourse.processing.org/t/does-the-mask-function-behave-differently-from-processing-to-p5/43357/2 "2023-12-02T21:23:45Z")

</div>

Hello @alignleft,

This was a challenge with p5.js but I got it sorted out.

See references to understand the difference:

- [https://p5js.org/reference/#/p5.Image/mask](https://p5js.org/reference/#/p5.Image/mask)
- [https://processing.org/reference/PImage\_mask\_.html](https://discourse.processing.org/t/reveal-image-of-the-masking/39215)

In _function setup()_:

```auto
  imgMask.filter(THRESHOLD, .5); 
  f1();
  img1.mask(imgMask); 

```

I had to set the alpha channel directly:

```auto
// May be faster using pixel array directly
function f1()
  {
  //imgMask.loadPixels();
  for (let x = 0; x < imgMask.width; x += 1) 
    {
    for (let y = 0; y < imgMask.height; y += 1) 
      {
      let c = imgMask.get(x, y);  
      let br = brightness(c); // 0 to 100 See color reference
      //let alph = alpha(c);
      //print(alph); // Confirmed that alpha was 255 by default.
      if (br==100)
        cm = color(0, 0);
      else
        cm = color(0, 255);
      imgMask.set(x, y, cm);
      }
    } 
  imgMask.updatePixels();         
  }

```

I also got it working directly with the _imgMask.pixels_ array and will leave that for the adventurous.

 ![image](https://canada1.discourse-cdn.com/flex036/uploads/processingfoundation1/original/3X/a/3/a3784cba2cc7759163a5aa410e7f301bfd57f929.jpeg)

`:)`

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