How to check for a color in an area

Processing Beginners
1

How can I check, if there is a specific color in an area?
Like:

If(color in area(10,100,50,600) == color(0,0,255)){
  run code
}
1 Like
2

Err, get(x,y) gives you one point

get with 4 parameters gives you a rectangle that you could loop over to check all points in it

3

If I use get with 4 parameters it says: Type mismatch,“processing.core.PImage” does not match with “int”

4

Yeah, using it with 4 parameters gives you an image (the section of the big image)

PImage section = get(…); // 4 parameters

Look at loadPixels and pixels to see how to for loop over it to check single points

5

With a for loop its too slow. I want to create a PacMan game where it should get checked fast to stop the character if a blue pixel is x+24 pixels next to it.

6

When you know it’s x+24 then use get with 2 parameters to get the color of this point

color testColor=get(x+24,y);

Test it against the color blue

7

can I also check if the color blue is in the area (x+24,y-24,x+24,y+24)?

8

Yes.

Theoretically

  • if he goes left check left,
  • when he goes right check right side.

so when you have the direction stored (int dir=0 or 1 or 2… for north, east, south, west) make the check accordingly.

Otherwise you have to write in full length:

if( get(x+24,y) == BLUE || 
   get(x-24,y) == BLUE ||
    .... ) { 
    // reached a wall
}

(|| means logical OR, && means logical AND)

This doesn’t make much sense because it would nearly always give you that PacMan reached a wall. So he wouldn’t be able to move anyway.

Instead, when you hit a cursor (or wasd keys) to make PacMan move, check only the direction for that key and allow the move or disallow move.

Chrisir

[EDITED]

1 Like
9

so is this the only way to set pixels?

loadPixels()
pixels[x+y*w] = color(255)
updatePixels()
10

… or use point() command

11