# 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:** 2
**Page:** 1
### Author:  [@alignleft](https://discourse.processing.org/u/alignleft)
#### Post date: [November 30, 2023, 3:01pm UTC](https://discourse.processing.org/t/does-the-mask-function-behave-differently-from-processing-to-p5/43357/1 "2023-11-30T15:01:00Z")
Hi 🙂
I have a working Processing sketch, that masks images using a thresholded clone of itself as a mask resulting in a replica of [this effect](https://www.instagram.com/p/Cq46KVPNi6Y/?img_index=1).
I am using the mask like this, in Processing, and everything works great:
```auto
// Storing image in *img* variable
PImage img = ...
// Cloning the image into *mask* variable
PImage mask = img.copy();
// Converting *mask* to black and white mask.
mask.filter(0.5, threshold);
// Applying mask to image
img.mask(mask);
// Drawing image
image(active, 0, 0);
```
I am trying to replicate the sketch in P5, but it seems like the [mask filter](https://p5js.org/reference/#/p5.Image/mask) only accepts png-files with an alpha channel.
Is it possible to mask the image in a similar, dynamic, way using p5?
---
### Author:  [@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")
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.
`:)`