Group similar hex codes in PHP

Question

I have the following color codes:

f3f3f3
f9f9f9

Visually, these two color codes are similar. How can I group them into one color or delete one of them?

If I try to use base_convert ($ hex, 16, 10) and get the difference between the values, the problem is that some colors are similar to the int value, but actually different visually. For instance:

# 484848 = 4737096 (gray)
# 4878a8 = 4749480 (blue) - visually there is a huge difference, but as the value of int the difference is small

and

# 183030 = 1585200 (grayish)
# 181818 = 1579032 (grayish) - both methods are fine

# 4878a8 = 4749480 (blue)
# a81818 = 11016216 (red) - the difference is huge, both visual and int value

Answer 1

Use hexdec to convert the hexadecimal decimal color code to its RGB equivalent. example (taken from hexdec ):

 <?php /** * Convert a hexa decimal color code to its RGB equivalent * * @param string $hexStr (hexadecimal color value) * @param boolean $returnAsString (if set true, returns the value separated by the separator character. Otherwise returns associative array) * @param string $seperator (to separate RGB values. Applicable only if second parameter is true.) * @return array or string (depending on second parameter. Returns False if invalid hex color value) */ function hex2RGB($hexStr, $returnAsString = false, $seperator = ',') { $hexStr = preg_replace("/[^0-9A-Fa-f]/", '', $hexStr); // Gets a proper hex string $rgbArray = array(); if (strlen($hexStr) == 6) { //If a proper hex code, convert using bitwise operation. No overhead... faster $colorVal = hexdec($hexStr); $rgbArray['red'] = 0xFF & ($colorVal >> 0x10); $rgbArray['green'] = 0xFF & ($colorVal >> 0x8); $rgbArray['blue'] = 0xFF & $colorVal; } elseif (strlen($hexStr) == 3) { //if shorthand notation, need some string manipulations $rgbArray['red'] = hexdec(str_repeat(substr($hexStr, 0, 1), 2)); $rgbArray['green'] = hexdec(str_repeat(substr($hexStr, 1, 1), 2)); $rgbArray['blue'] = hexdec(str_repeat(substr($hexStr, 2, 1), 2)); } else { return false; //Invalid hex color code } return $returnAsString ? implode($seperator, $rgbArray) : $rgbArray; // returns the rgb string or the associative array } ?> 

CONCLUSION:

 hex2RGB("#FF0") -> array( red =>255, green => 255, blue => 0) hex2RGB("#FFFF00) -> Same as above hex2RGB("#FF0", true) -> 255,255,0 hex2RGB("#FF0", true, ":") -> 255:255:0 

than, get red, green and blue deltas to get the distance from the flowers.