mirror of
https://github.com/pixelfed/pixelfed.git
synced 2024-11-27 00:33:17 +00:00
34 lines
1.1 KiB
PHP
34 lines
1.1 KiB
PHP
|
<?php
|
||
|
|
|
||
|
|
namespace App\Util\Blurhash;
|
||
|
|
|
||
|
|
final class AC {
|
||
|
|
|
||
|
|
public static function encode(array $value, float $max_value): float {
|
||
|
|
$quant_r = static::quantise($value[0] / $max_value);
|
||
|
|
$quant_g = static::quantise($value[1] / $max_value);
|
||
|
|
$quant_b = static::quantise($value[2] / $max_value);
|
||
|
|
return $quant_r * 19 * 19 + $quant_g * 19 + $quant_b;
|
||
|
|
}
|
||
|
|
|
||
|
|
public static function decode(int $value, float $max_value): array {
|
||
|
|
$quant_r = floor($value / (19 * 19));
|
||
|
|
$quant_g = floor($value / 19) % 19;
|
||
|
|
$quant_b = $value % 19;
|
||
|
|
|
||
|
|
return [
|
||
|
|
static::signPow(($quant_r - 9) / 9, 2) * $max_value,
|
||
|
|
static::signPow(($quant_g - 9) / 9, 2) * $max_value,
|
||
|
|
static::signPow(($quant_b - 9) / 9, 2) * $max_value
|
||
|
|
];
|
||
|
|
}
|
||
|
|
|
||
|
|
private static function quantise(float $value): float {
|
||
|
|
return floor(max(0, min(18, floor(static::signPow($value, 0.5) * 9 + 9.5))));
|
||
|
|
}
|
||
|
|
|
||
|
|
private static function signPow(float $base, float $exp): float {
|
||
|
|
$sign = $base <=> 0;
|
||
|
|
return $sign * pow(abs($base), $exp);
|
||
|
|
}
|
||
|
|
}
|