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Add Blurhash encoder
This commit is contained in:
Daniel Supernault
parent
4d22426da2
commit
fad102bf80
5 changed files with 255 additions and 0 deletions
34
app/Util/Blurhash/AC.php
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34
app/Util/Blurhash/AC.php
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<?php
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namespace App\Util\Blurhash;
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final class AC {
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public static function encode(array $value, float $max_value): float {
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$quant_r = static::quantise($value[0] / $max_value);
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$quant_g = static::quantise($value[1] / $max_value);
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$quant_b = static::quantise($value[2] / $max_value);
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return $quant_r * 19 * 19 + $quant_g * 19 + $quant_b;
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}
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public static function decode(int $value, float $max_value): array {
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$quant_r = floor($value / (19 * 19));
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$quant_g = floor($value / 19) % 19;
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$quant_b = $value % 19;
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return [
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static::signPow(($quant_r - 9) / 9, 2) * $max_value,
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static::signPow(($quant_g - 9) / 9, 2) * $max_value,
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static::signPow(($quant_b - 9) / 9, 2) * $max_value
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];
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}
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private static function quantise(float $value): float {
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return floor(max(0, min(18, floor(static::signPow($value, 0.5) * 9 + 9.5))));
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}
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private static function signPow(float $base, float $exp): float {
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$sign = $base <=> 0;
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return $sign * pow(abs($base), $exp);
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}
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}
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39
app/Util/Blurhash/Base83.php
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39
app/Util/Blurhash/Base83.php
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<?php
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namespace App\Util\Blurhash;
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use InvalidArgumentException;
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class Base83 {
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private const ALPHABET = [
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'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D',
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'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R',
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'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
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'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
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'u', 'v', 'w', 'x', 'y', 'z', '#', '$', '%', '*', '+', ',', '-', '.',
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':', ';', '=', '?', '@', '[', ']', '^', '_', '{', '|', '}', '~'
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];
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private const BASE = 83;
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public static function encode(int $value, int $length): string {
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if (floor($value / (self::BASE ** $length)) != 0) {
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throw new InvalidArgumentException('Specified length is too short to encode given value.');
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}
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$result = '';
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for ($i = 1; $i <= $length; $i++) {
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$digit = floor($value / (self::BASE ** ($length - $i))) % self::BASE;
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$result .= self::ALPHABET[$digit];
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}
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return $result;
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}
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public static function decode(string $hash): int {
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$result = 0;
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foreach (str_split($hash) as $char) {
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$result = $result * self::BASE + (int) array_search($char, self::ALPHABET, true);
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}
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return (int) $result;
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}
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}
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139
app/Util/Blurhash/Blurhash.php
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139
app/Util/Blurhash/Blurhash.php
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<?php
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namespace App\Util\Blurhash;
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use InvalidArgumentException;
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class Blurhash {
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public static function encode(array $image, int $components_x = 4, int $components_y = 4, bool $linear = false): string {
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if (($components_x < 1 || $components_x > 9) || ($components_y < 1 || $components_y > 9)) {
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throw new InvalidArgumentException("x and y component counts must be between 1 and 9 inclusive.");
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}
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$height = count($image);
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$width = count($image[0]);
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$image_linear = $image;
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if (!$linear) {
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$image_linear = [];
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for ($y = 0; $y < $height; $y++) {
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$line = [];
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for ($x = 0; $x < $width; $x++) {
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$pixel = $image[$y][$x];
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$line[] = [
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Color::toLinear($pixel[0]),
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Color::toLinear($pixel[1]),
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Color::toLinear($pixel[2])
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];
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}
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$image_linear[] = $line;
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}
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}
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$components = [];
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$scale = 1 / ($width * $height);
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for ($y = 0; $y < $components_y; $y++) {
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for ($x = 0; $x < $components_x; $x++) {
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$normalisation = $x == 0 && $y == 0 ? 1 : 2;
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$r = $g = $b = 0;
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for ($i = 0; $i < $width; $i++) {
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for ($j = 0; $j < $height; $j++) {
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$color = $image_linear[$j][$i];
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$basis = $normalisation
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* cos(M_PI * $i * $x / $width)
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* cos(M_PI * $j * $y / $height);
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$r += $basis * $color[0];
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$g += $basis * $color[1];
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$b += $basis * $color[2];
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}
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}
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$components[] = [
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$r * $scale,
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$g * $scale,
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$b * $scale
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];
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}
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}
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$dc_value = DC::encode(array_shift($components) ?: []);
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$max_ac_component = 0;
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foreach ($components as $component) {
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$component[] = $max_ac_component;
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$max_ac_component = max ($component);
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}
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$quant_max_ac_component = (int) max(0, min(82, floor($max_ac_component * 166 - 0.5)));
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$ac_component_norm_factor = ($quant_max_ac_component + 1) / 166;
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$ac_values = [];
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foreach ($components as $component) {
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$ac_values[] = AC::encode($component, $ac_component_norm_factor);
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}
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$blurhash = Base83::encode($components_x - 1 + ($components_y - 1) * 9, 1);
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$blurhash .= Base83::encode($quant_max_ac_component, 1);
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$blurhash .= Base83::encode($dc_value, 4);
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foreach ($ac_values as $ac_value) {
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$blurhash .= Base83::encode((int) $ac_value, 2);
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}
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return $blurhash;
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}
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public static function decode (string $blurhash, int $width, int $height, float $punch = 1.0, bool $linear = false): array {
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if (empty($blurhash) || strlen($blurhash) < 6) {
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throw new InvalidArgumentException("Blurhash string must be at least 6 characters");
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}
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$size_info = Base83::decode($blurhash[0]);
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$size_y = floor($size_info / 9) + 1;
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$size_x = ($size_info % 9) + 1;
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$length = (int) strlen($blurhash);
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$expected_length = (int) (4 + (2 * $size_y * $size_x));
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if ($length !== $expected_length) {
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throw new InvalidArgumentException("Blurhash length mismatch: length is {$length} but it should be {$expected_length}");
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}
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$colors = [DC::decode(Base83::decode(substr($blurhash, 2, 4)))];
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$quant_max_ac_component = Base83::decode($blurhash[1]);
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$max_value = ($quant_max_ac_component + 1) / 166;
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for ($i = 1; $i < $size_x * $size_y; $i++) {
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$value = Base83::decode(substr($blurhash, 4 + $i * 2, 2));
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$colors[$i] = AC::decode($value, $max_value * $punch);
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}
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$pixels = [];
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for ($y = 0; $y < $height; $y++) {
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$row = [];
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for ($x = 0; $x < $width; $x++) {
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$r = $g = $b = 0;
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for ($j = 0; $j < $size_y; $j++) {
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for ($i = 0; $i < $size_x; $i++) {
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$color = $colors[$i + $j * $size_x];
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$basis =
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cos((M_PI * $x * $i) / $width) *
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cos((M_PI * $y * $j) / $height);
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$r += $color[0] * $basis;
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$g += $color[1] * $basis;
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$b += $color[2] * $basis;
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}
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}
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$row[] = $linear ? [$r, $g, $b] : [
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Color::toSRGB($r),
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Color::toSRGB($g),
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Color::toSRGB($b)
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];
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}
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$pixels[] = $row;
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}
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return $pixels;
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}
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}
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19
app/Util/Blurhash/Color.php
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19
app/Util/Blurhash/Color.php
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<?php
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namespace App\Util\Blurhash;
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final class Color {
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public static function toLinear(int $value): float {
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$value = $value / 255;
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return ($value <= 0.04045)
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? $value / 12.92
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: pow(($value + 0.055) / 1.055, 2.4);
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}
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public static function tosRGB(float $value): int {
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$normalized = max(0, min(1, $value));
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return ($normalized <= 0.0031308)
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? (int) round($normalized * 12.92 * 255 + 0.5)
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: (int) round((1.055 * pow($normalized, 1 / 2.4) - 0.055) * 255 + 0.5);
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}
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}
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24
app/Util/Blurhash/DC.php
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24
app/Util/Blurhash/DC.php
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<?php
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namespace App\Util\Blurhash;
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final class DC {
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public static function encode(array $value): int {
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$rounded_r = Color::tosRGB($value[0]);
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$rounded_g = Color::tosRGB($value[1]);
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$rounded_b = Color::tosRGB($value[2]);
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return ($rounded_r << 16) + ($rounded_g << 8) + $rounded_b;
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}
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public static function decode(int $value): array {
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$r = $value >> 16;
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$g = ($value >> 8) & 255;
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$b = $value & 255;
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return [
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Color::toLinear($r),
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Color::toLinear($g),
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Color::toLinear($b)
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];
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}
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}
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