Vectors and Obstacles HELP 2

Programming Questions

kbwhi1

in Programming Questions • 1 year ago

Hello again,

I am still struggling to have my vectors read the background image. I want my ellipses to change directions when they reach a black obstacle on the background image. At the moment I am using:

void avoid() {
      for (int i = 0; i < ballCollection.size(); i++) {
      color locationColour = get (int(loc.x), int(loc.y));
if (locationColour != -1) {    //if locationColour is not equal to white

        speed.x = speed.x * -1;
        speed.y = speed.y * -1;
      }
    }
}

It is not working at all. I tested if it is reading the backround colour by using :

void display() {
for (int i = 0; i < ballCollection.size(); i++) {
color locationColour = get (int(loc.x), int(loc.y));

if (locationColour != -1) {
    fill(255,0,0);
      }
if (locationColour == -1){
   fill(0,255,0);
}
}
    noStroke();
    ellipse(loc.x, loc.y, 5, 5);
}

and it did seem to be reading the background gif...

does anyone know how to use background images (black and white two bif gifs) as obstacles??

Thanks

kbwhi1

Replies(2)

PhiLho

Re: Vectors and Obstacles HELP 2

1 year ago

It depends... on the remainder of your code!
If you display your image on the sketch, it can work.
But since you already loaded the image in a PImage, it is simpler to check directly the pixels in it. So, instead of doing get(int(loc.x), int(loc.y)); do obstacles.get(int(loc.x), int(loc.y)); ie. the same thing, but applied to the image itself (named here obstacles, change the name to your).
And, as I advised in the other thread, test against a real color, not a number: if (locationColour != #FFFFFF) is better to check white.
See also the What is a color in Processing? article.

quarks

Re: Vectors and Obstacles HELP 2

1 year ago

Testing for colours can be confusing since the value is stored in an int whcih is a signed integer, but it represents 4 unsigned values ARGB. It is made harder since A is most often 255 causing the integer value to be negative.

One way is to use hexadecimal notaion as in Phi.Lho's post, which although my prefered option requires the user to be familiar with heaxdecimal. The alternative would be to use the color() method to calculate it for you e.g.

int white = color(255);

if (locationColour != white)

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