复制自this SO AnswerCullub。
此代码完美地将用户电子邮件转换为用户头像颜色。经过长时间的搜索，我得到了正确的十六进制值，类似于在前端使用 javascript 生成的十六进制值。
TL;DR：完整的代码可以在这里找到Pastebin。
/**
* convert user email to hsl for user avatar
* @param string $string
* @return string HEX color code
*/
function stringToColor($string)
{
$hash = 0;
$l = 70;
$s = 60;
for ($i = 0; $i < strlen($string); $i++) {
$hash = ord($string[$i]) + (($hash << 5) - $hash);
}
$h = fmod($hash, 360);
return $this->hslToHex($h, $s, $l, true);
}
/**
* Converts HSL to Hex by converting it to
* RGB, then converting that to hex.
*
* string hslToHex($h, $s, $l[, $prependPound = true]
*
* $h is the Degrees value of the Hue
* $s is the Percentage value of the Saturation
* $l is the Percentage value of the Lightness
* $prependPound is a bool, whether you want a pound
* sign prepended. (optional - default=true)
*
* Calls:
* hslToRgb
*
* Output: Hex in the format: #00ff88 (with
* pound sign). Rounded to the nearest whole
* number.
*/
function hslToHex($h, $s, $l, $prependPound = true)
{
//convert hsl to rgb
$rgb = $this->hslToRgb($h, $s, $l);
//convert rgb to hex
$hexR = $rgb['r'];
$hexG = $rgb['g'];
$hexB = $rgb['b'];
//round to the nearest whole number
$hexR = round($hexR);
$hexG = round($hexG);
$hexB = round($hexB);
//convert to hex
$hexR = dechex($hexR);
$hexG = dechex($hexG);
$hexB = dechex($hexB);
//check for a non-two string length
//if it's 1, we can just prepend a
//0, but if it is anything else non-2,
//it must return false, as we don't
//know what format it is in.
if (strlen($hexR) != 2) {
if (strlen($hexR) == 1) {
//probably in format #0f4, etc.
$hexR = "0" . $hexR;
} else {
//unknown format
return false;
}
}
if (strlen($hexG) != 2) {
if (strlen($hexG) == 1) {
$hexG = "0" . $hexG;
} else {
return false;
}
}
if (strlen($hexB) != 2) {
if (strlen($hexB) == 1) {
$hexB = "0" . $hexB;
} else {
return false;
}
}
//if prependPound is set, will prepend a
//# sign to the beginning of the hex code.
//(default = true)
$hex = "";
if ($prependPound) {
$hex = "#";
}
$hex = $hex . $hexR . $hexG . $hexB;
return $hex;
}
/**
* Converts an HSL color value to RGB. Conversion formula
* adapted from http://www.niwa.nu/2013/05/math-behind-colorspace-conversions-rgb-hsl/.
* Assumes h, s, and l are in the format Degrees,
* Percent, Percent, and returns r, g, and b in
* the range [0 - 255].
*
* Called by hslToHex by default.
*
* Calls:
* degPercPercToHsl
* hueToRgb
*
* @param Number h The hue value
* @param Number s The saturation level
* @param Number l The luminence
* @return Array The RGB representation
*/
function hslToRgb($h, $s, $l)
{
//convert the hue's 360 degrees in a circle to 1
$h /= 360;
//convert the saturation and lightness to the 0-1
//range by multiplying by 100
$s /= 100;
$l /= 100;
//If there's no saturation, the color is a greyscale,
//so all three RGB values can be set to the lightness.
//(Hue doesn't matter, because it's grey, not color)
if ($s == 0) {
$r = $l * 255;
$g = $l * 255;
$b = $l * 255;
} else {
//calculate some temperary variables to make the
//calculation eaisier.
if ($l < 0.5) {
$temp2 = $l * (1 + $s);
} else {
$temp2 = ($l + $s) - ($s * $l);
}
$temp1 = 2 * $l - $temp2;
//run the calculated vars through hueToRgb to
//calculate the RGB value. Note that for the Red
//value, we add a third (120 degrees), to adjust
//the hue to the correct section of the circle for
//red. Simalarly, for blue, we subtract 1/3.
$r = 255 * $this->hueToRgb($temp1, $temp2, $h + (1 / 3));
$g = 255 * $this->hueToRgb($temp1, $temp2, $h);
$b = 255 * $this->hueToRgb($temp1, $temp2, $h - (1 / 3));
}
$rgb['r'] = $r;
$rgb['g'] = $g;
$rgb['b'] = $b;
return $rgb;
// return "rgb($r, $g, $b)";
}
/**
* Converts an HSL hue to it's RGB value.
*
* Input: $temp1 and $temp2 - temperary vars based on
* whether the lumanence is less than 0.5, and
* calculated using the saturation and luminence
* values.
* $hue - the hue (to be converted to an RGB
* value) For red, add 1/3 to the hue, green
* leave it alone, and blue you subtract 1/3
* from the hue.
*
* Output: One RGB value.
*
* Thanks to Easy RGB for this function (Hue_2_RGB).
* http://www.easyrgb.com/index.php?X=MATH&$h=19#text19
*
*/
function hueToRgb($temp1, $temp2, $hue)
{
if ($hue < 0) {
$hue += 1;
}
if ($hue > 1) {
$hue -= 1;
}
if ((6 * $hue) < 1) {
return ($temp1 + ($temp2 - $temp1) * 6 * $hue);
} elseif ((2 * $hue) < 1) {
return $temp2;
} elseif ((3 * $hue) < 2) {
return ($temp1 + ($temp2 - $temp1) * ((2 / 3) - $hue) * 6);
}
return $temp1;
}