Weird behaviour (colormode)

Aedoro

This is a pretty short question, in the following code line 10 is commented out and nothing is visible. But when it is not commented out we do see a WHITE dot. What is happening? That line doesn't do anything?

void setup() {
    size(300,300);
}

void draw() {
    background(color(0));

    strokeWeight(width/2);

    //color c1 = color(255); // works when enabled (but this doesnt do anything?)

    colorMode(ADD);
    stroke(color(255,0,0,255));

    point(width/2,height/2);  

    colorMode(BLEND);
}

quark

The problem are in lines 13 and 18 since the constants ADD and BLEND are not valid arguments so their action is unpredictable. If you comment these 2 lines out then line 11 has no effect on the display which is a red circle.

Also note that the colorMode is not reset at the start of draw

GoToLoop

https://GitHub.com/processing/processing/issues

quark

Are you suggesting it is an issue or the OP should post an issue?

GoToLoop

It's not pointing at any particular issue. So it implies the OP should consider posting his own. :\">

jeremydouglass

@Aedoro --

From the colorMode reference -- https://processing.org/reference/colorMode_.html :

mode: Either RGB or HSB, corresponding to Red/Green/Blue and Hue/Saturation/Brightness

You are using the mode keywords from blendMode() -- https://processing.org/reference/blendMode_.html :

BLEND, ADD, SUBTRACT, DARKEST, LIGHTEST, DIFFERENCE, EXCLUSION, MULTIPLY, SCREEN, REPLACE

Use the correctly paired command and keywords according to what you are trying to accomplish.

When you ask: "What is happening?" the answer is that these keywords have numerical equivalents -- the value of blendMode keyword "ADD" (2) is the same as the value of the colorMode keyword "ALPHA" (2) and the value of "BLEND" (1) is the same as "RGB" (1).

• https://github.com/processing/processing/blob/0abee5af6ad3b11cf2b73bb794b8a97c157c4762/core/src/processing/core/PConstants.java#L227

  static final int RGB   = 1;  // image & color
  static final int ARGB  = 2;  // image
  static final int HSB   = 3;  // color
  static final int ALPHA = 4;  // image
  

• https://github.com/processing/processing/blob/0abee5af6ad3b11cf2b73bb794b8a97c157c4762/core/src/processing/core/PConstants.java#L258

  public final static int REPLACE    = 0;
  public final static int BLEND      = 1 << 0;
  public final static int ADD        = 1 << 1;
  

1 << 0 = binary 01 = 1
1 << 1 = binary 10 = 2

So when you write:

colorMode(ADD);    // 2
colorMode(BLEND);  // 1

...that doesn't mean anything (the keyword names are invalid), but it gets run as if you had written:

colorMode(ALPHA);  // 2
colorMode(RGB);    // 1