Mask() can only be used with an image that's the same size

py5
1

Can anyone please explain the error mask() can only be used with an image that's the same size.? Every time I try to use a Py5Graphics object/image as a mask, I run into that error. But the image loaded is the same pixel size as Py5Graphic object both 200x200px.

What am I missing? :face_with_peeking_eye:

Sample code

import py5


def setup():
    global pg, img
    py5.size(400, 400)
    py5.background(100)
    pg = py5.create_graphics(200, 200)
    img = py5.load_image("sq.jpg")  # image is 200x200px


def draw():
    pg.begin_draw()
    pg.background(255)
    pg.fill(0)
    pg.circle(pg.width / 2, pg.height / 2, 150)
    pg.end_draw()
    
    img.mask(pg)
    py5.image(img, 50, 50)


py5.run_sketch()

cut-out-shapes.py", line 19, in draw
    12   def draw():
 (...)
    15       pg.fill(0)
    16       pg.circle(pg.width / 2, pg.height / 2, 150)
    17       pg.end_draw()
    18       
--> 19       img.mask(pg)
    20       py5.image(img, 50, 50)
    ..................................................
     pg = Py5Graphics(width=200, height=200)
    ..................................................

java.lang.IllegalArgumentException: java.lang.IllegalArgumentException: mask() can only be used with an image that's the same size.
2

Hello @SNitaine,

Try printing out the size to verify, setting it exactly or using resize().

This is a working Processing example:

// Masking
// v1.0.0
// GLV 2021-07-24

PGraphics pg1;
PImage img1;

void setup() 
  {
  size(300, 300);
  
  String urlString = "http://learningprocessing.com/code/assets/sunflower.jpg";
  img1 = loadImage(urlString);
  println(img1.width, img1.height);
  
  pg1 = createGraphics(300, 300); //IllegalArgumentException: mask() can only be used with an image that's the same size.
  pg1 = createGraphics(img1.width, img1.height);
  //img1.resize(pg1.width, pg1.height);
  }

void draw() 
  {
  background(255, 255, 0);

  pg1.beginDraw();
  pg1.background(255);
  pg1.fill(0);
  pg1.circle(pg1.width/2, pg1.height/2, 150);
  pg1.endDraw();
  
  img1.mask(pg1);
  
  image(img1, 0, 0);
  }

:)

3

This is the Java source code that throws that exception:

Somehow, the corresponding pixels[] from pg & img aren’t matching for len()!

Debug them using load_pixels() at the end of setup():

pg.load_pixels(); img.load_pixels()

print(
    pg_len := len(pg.pixels),
    img_len := len(img.pixels), # 200 x 200 px must be 40_000 pixels
    pg_len == img_len,
    sep='\n'
)

If they’re indeed of different len(), you might try out the py5.pixel_density(1) workaround (no guarantees though):

1 Like
4

Yes @GoToLoop you are correct, the pixels aren’t the same density.

pg.load_pixels()
print("pg pixels: ", len(pg.pixels))
print("pg density: ", pg.pixel_density)
img.load_pixels()
print("img pixels: ", len(img.pixels))
print("img density:", img.pixel_density)

Prints the following output

pg pixels:  160000
pg density:  2
img pixels:  40000
img density: 1

Indeed setting py5.pixel_density(1) fixes the issues.

pg pixels:  40000
pg density:  1
img pixels:  40000
img density: 1

Thanks :ok_hand:

2 Likes