Create Colors based on # of Items

[nick1]

Preferably using PHP, I'd like to create X number of colors based on X number of items and using a predefined color range. For example:

 

ITEM

VALUE

1

1,234,567,890

2

234,567,890

3

34,567,890

4

4,567,890

5

567,890

 

 

Color Range

red = largest value

green = medium value

blue = smallest value

 

 

Example

Item 1 gets color red

Item 2 gets whatever color naturally comes between red and green

Item 3 gets color green

Item 4 gets whatever color naturally comes between green and blue

Item 5 gets color blue

 

 

Requirements

The code should be able to handle any number of items. 5 items was just an easy example.

 

 

Some Thoughts

- Number of items = number of colors

- How to divide a color range into number of items?

- Colors can be represented in decimal format: red=255,000,000 blue=000,000,255

- Can a formula be created, based on the color decimal format, to solve this problem?

 

 

I think it's the math portion of the problem that I'm stuck on right now.

Thanks for your help,

 

Nick

[phil88]

You could decrease the red value by x and increase green by x for every item from the 1st to the middle item. Then you decrease the green value by x and increase the blue value by x for every item until you reach the last item. x will have the same value throughout because you can work it out based on the number of items.

 

Here's some psuedocode to help explain what I mean;

$numItems = count($items);
$middleItem = $numItems / 2;

$red = 255;
$green = 0;
$blue = 0;
$x = ?;

foreach($items as $index => $item){
if($index < $middleItem){
	$red -= $x;
	$green += $x;
}else{
	// $red should be 0 by now if $x is set correctly
	// $green should be 255
	$green -= $x;
	$blue += $x;
}

echo $item in the colour rbg($red, $green, $blue);
}

 

I left you to work out how you figure out what the increment/decrement ($x) should be

 

 

[nick1]

Thank you for your help! You showed me how to approach the problem from a different view - that's exactly the kind of help I needed. :-)

 

Nick

[jcbones]

Because this is an interesting proposal, I added a little code to the example above.  It isn't perfect, as you can see if you un-comment the for loop, it kinda works.  As was stated, getting $x is the big issue.

<?php
$items[] = 1234567890;
$items[] = 234567890;
$items[] = 34567890;
$items[] = 4567890;
$items[] = 567890;

// for($i = 0; $i < 100; $i++) {
// $items[] = mt_rand();
// }
// rsort($items);

$red = 255;
$green = 0;
$blue = 0;



$middleNum = round((count($items) / 2) - 1); //Gets the middle index of the array.
$x = floor(255 / $middleNum);

foreach($items as $index => $item){	
if($index > 0 && $index <= $middleNum){
	$red -= $x;
	$green += $x;		
}elseif($index > $middleNum) {
	$green -= $x;
	$blue += $x;
}
echo number_format($item) . " is rgb($red,$green,$blue);<br />";
}
?>