Processing 1.0 - Processing Discourse - Manipulating Color Datatype

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Manipulating Color Datatype (Read 682 times)

JimAtArtsnova

Manipulating Color Datatype
Aug 26^th, 2008, 6:24am

Hi,

I would just like a confirmation on a problem I'm wrestling with. I have an array of type color. From searching around, it seems that there are no functions available for modifying the ARGB info once it is in the color variable. For example if I want to add or subtract red, I have to pull out individually the ARGB components into separate variables, make the modification(s), and then stick them all back into the color variable. Is this correct?

Thanks.

Jim

PhiLho YaBB Moderator Offline Posts: 4190 Near Paris (France)	Re: Manipulating Color Datatype Reply #1 - Aug 26^th, 2008, 8:21am Yes, that's correct. Of course, you can do these functions yourself.

JimAtArtsnova

Re: Manipulating Color Datatype
Reply #2 - Aug 26^th, 2008, 2:47pm

Hi PhiLho,

Thanks for confirming. I was hoping to be able to avoid doing this myself. Seems like it could be useful to add functions for manipulating the ARGB components into Processing itself.

I suppose that I could write functions that would take arguments for color and 1-4 of the color components and then figure out how to do bitwise or's on the color value.

Given the size of the color arrays I anticipate having, I was really hoping for something more efficient than what I could produce.

Jim

JohnG Ex Member	Re: Manipulating Color Datatype Reply #3 - Aug 26^th, 2008, 4:50pm unfortunately color isn't actually a datatype.. it's just a synonym for int behind the scenes, hence why there are no built in methods for it.

Jo Wood

Re: Manipulating Color Datatype
Reply #4 - Aug 26^th, 2008, 6:26pm

You can convert between Processing's use of integers to represent colours and Java's own Color class though. That then allows you to manipulate the individual components without resorting to bit manipulation. It also gives you access to Java's colour methods such as conversion to HSB, interpretation of HTML style hex colours etc.

A simple example:

Quote:

int myCol1, myCol2, myCol3;

void setup()
{
  size(400,400);
  smooth();

  // Original Processing colour.
  myCol1 = color(200,150,50,255);

  // Create a Java Color object from Processing colour.
  Color javaCol = new Color(myCol1);

  // Darken Java colour and then convert to processing colour.
  myCol2 = javaCol.darker().getRGB();

  // Create processing colour with boosted green from Java colour components.
  int r=javaCol.getRed();
  int g=javaCol.getGreen();
  int b=javaCol.getBlue();
  int a=javaCol.getAlpha();
  myCol3 = color(r/2,g,b/2,a);
}

void draw()
{
  background(255);

  fill(myCol1);
  ellipse(width/2,height*.25,100,100);
  fill(myCol2);
  ellipse(width/2,height*.5,100,100);
  fill(myCol3);
  ellipse(width/2,height*.75,100,100);
}

PhiLho

Re: Manipulating Color Datatype
Reply #5 - Aug 26^th, 2008, 6:33pm

As pointed out, color is just an int, so if Processing provided functions to set an individual component, it wouldn't be more efficient than those you would write.
Actually, these functions could even be slower: see how blue() (for example) is slower than direct bit access, because of additional treatment.

Quick, rough implementation:
Code:

color setBlue(color c, int b)
{
  return (c & 0xFFFFFF00) | b;
}
color setGreen(color c, int g)
{
  return (c & 0xFFFF00FF) | (g << 8);
}
color setRed(color c, int r)
{
  return (c & 0xFF00FFFF) | (r << 16);
}
color setAlpha(color c, int a)
{
  return (c & 0x00FFFFFF) | (a << 24);
}

void setup()
{
  color c = color(50, 100, 150);
  c = setBlue(c, 128);
  println(hex(c));
  c = setGreen(c, 128);
  println(hex(c));
  c = setRed(c, 128);
  println(hex(c));
  c = setAlpha(c, 128);
  println(hex(c));
}

JimAtArtsnova

Re: Manipulating Color Datatype
Reply #6 - Aug 26^th, 2008, 9:02pm

Hi Jo,

I was writing in reference to the Color class. Looking through the associated methods at:

http://java.sun.com/j2se/1.4.2/docs/api/java/awt/Color.html

you will see that there are numerous methods provided for retrieving the color information, but there are no methods provided for modifying the information within that color object.

For example, an alterGreen(int valu) method where I could either increase or decrease the amount of green would be really nice. Same for each of the other components.

PhiLho: thanks for the sample code. On the plus side, anything I come up with for this particular sketch would be useful in similar situations in other sketches.

Speaking of which, is anyone aware of any libraries that may have been developed which contain this sort of functionality?

Thanks, Jim

PhiLho YaBB Moderator Offline Posts: 4190 Near Paris (France)	Re: Manipulating Color Datatype Reply #7 - Aug 27^th, 2008, 4:44pm Ah, I was mistaken. Well, Color objects, like the String one, for example, is immutable, which is seen as good design nowadays. Ie. you don't change such object, but create a new object with given change (like darken and brighten methods do). If you want a mutable object, I fear you have to write your own class.

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