I'm looking for a function that can accurately represent the distance between two colours as a number or something.
For example I am looking to have an array of HEX values or RGB arrays and I want to find the most similar colour in the array for a given colour
eg. I pass a function a RGB value and the 'closest' colour in the array is returned
In the end, despite the wonderful suggestions surrounding imagemagick I found a good solution using straight php. I was able to calculate the closest color through the use of delta E 2000 with a modified version of php-color-difference library found on github, here is my fork: https://github.com/nalipaz/php-color-difference
The pertinent example is:
<?php
include('lib/color_difference.class.php');
$palette = array(
'00' => array(255, 255, 255),
'01' => array(0, 0, 0),
'02' => array(0, 0, 139),
'03' => array(0, 128, 0),
'04' => array(255, 0, 0),
'05' => array(139, 0, 0),
'06' => array(128, 0, 128),
'07' => array(255, 165, 0),
'08' => array(255, 255, 0),
'09' => array(50, 205, 50),
'10' => array(0, 128, 128),
'11' => array(173, 216, 230),
'12' => array(0, 0, 255),
'13' => array(255, 105, 180),
'14' => array(128, 128, 128),
'15' => array(211, 211, 211),
);
$color_rgb = array(255, 255, 128);
$color_delta_e = new color_difference($color_rgb);
$match_index = $color_delta_e->getClosestMatch($palette);
$color = $palette[$match_index];
I am pretty happy with this solution and smaller amount of overhead. Thanks for the suggestions guys.
Use preg_replace_callback:
function mycallback($matches) {
$bindings = array(
0=>'white',
1=>'black',
2=>'blue',
3=>'green',
4=>'red',
5=>'brown',
6=>'purple',
);
$fg = isset($bindings[$matches[1]]) ? $bindings[$matches[1]] : 'transparent';
$bg = isset($bindings[$matches[2]]) ? $bindings[$matches[2]] : 'transparent';
return '<span style="color: '.$fg.'; background: '.$bg.';">'.$matches[3].'</span>';
}
$str = '^C3,1Hello^C foo ^C6,2World^C';
$str = preg_replace_callback('/^C([0-9]{1,2}),?([0-9]{1,2})(.*?)^C/', 'mycallback', $str);
echo $str;
I once set up a hexagonal coordinate system in a game so that the y-axis was at a 60-degree angle to the x-axis. This avoids the odd-even row distinction.
(source: althenia.net)
The distance in this coordinate system is:
dx = x1 - x0
dy = y1 - y0
if sign(dx) == sign(dy)
abs(dx + dy)
else
max(abs(dx), abs(dy))
You can convert (x', y) from your coordinate system to (x, y) in this one using:
x = x' - floor(y/2)
So dx becomes:
dx = x1' - x0' - floor(y1/2) + floor(y0/2)
Careful with rounding when implementing this using integer division. In C for int y floor(y/2) is (y%2 ? y-1 : y)/2.
You can iterate over the matrix and find the coordinates of all the 1's (x1, y1). Then for each position in the cell (x2, y2), for all (x1, y1) in your list, find the minimum |x2 - x1| + |y2 - y1| (the Manhattan distance since it's a grid).
Each color is represented as a tuple in the HEX code. To determine close matches you need to subtract each RGB component separately.
Example:
edit
So you want the closest named color? Create an array with the hex values of each color, iterate it and return the name. Something like this;