<?php namespace App\Util\Blurhash; use InvalidArgumentException; class Blurhash { public static function encode(array $image, int $components_x = 4, int $components_y = 4, bool $linear = false): string { if (($components_x < 1 || $components_x > 9) || ($components_y < 1 || $components_y > 9)) { throw new InvalidArgumentException("x and y component counts must be between 1 and 9 inclusive."); } $height = count($image); $width = count($image[0]); $image_linear = $image; if (!$linear) { $image_linear = []; for ($y = 0; $y < $height; $y++) { $line = []; for ($x = 0; $x < $width; $x++) { $pixel = $image[$y][$x]; $line[] = [ Color::toLinear($pixel[0]), Color::toLinear($pixel[1]), Color::toLinear($pixel[2]) ]; } $image_linear[] = $line; } } $components = []; $scale = 1 / ($width * $height); for ($y = 0; $y < $components_y; $y++) { for ($x = 0; $x < $components_x; $x++) { $normalisation = $x == 0 && $y == 0 ? 1 : 2; $r = $g = $b = 0; for ($i = 0; $i < $width; $i++) { for ($j = 0; $j < $height; $j++) { $color = $image_linear[$j][$i]; $basis = $normalisation * cos(M_PI * $i * $x / $width) * cos(M_PI * $j * $y / $height); $r += $basis * $color[0]; $g += $basis * $color[1]; $b += $basis * $color[2]; } } $components[] = [ $r * $scale, $g * $scale, $b * $scale ]; } } $dc_value = DC::encode(array_shift($components) ?: []); $max_ac_component = 0; foreach ($components as $component) { $component[] = $max_ac_component; $max_ac_component = max ($component); } $quant_max_ac_component = (int) max(0, min(82, floor($max_ac_component * 166 - 0.5))); $ac_component_norm_factor = ($quant_max_ac_component + 1) / 166; $ac_values = []; foreach ($components as $component) { $ac_values[] = AC::encode($component, $ac_component_norm_factor); } $blurhash = Base83::encode($components_x - 1 + ($components_y - 1) * 9, 1); $blurhash .= Base83::encode($quant_max_ac_component, 1); $blurhash .= Base83::encode($dc_value, 4); foreach ($ac_values as $ac_value) { $blurhash .= Base83::encode((int) $ac_value, 2); } return $blurhash; } public static function decode (string $blurhash, int $width, int $height, float $punch = 1.0, bool $linear = false): array { if (empty($blurhash) || strlen($blurhash) < 6) { throw new InvalidArgumentException("Blurhash string must be at least 6 characters"); } $size_info = Base83::decode($blurhash[0]); $size_y = floor($size_info / 9) + 1; $size_x = ($size_info % 9) + 1; $length = (int) strlen($blurhash); $expected_length = (int) (4 + (2 * $size_y * $size_x)); if ($length !== $expected_length) { throw new InvalidArgumentException("Blurhash length mismatch: length is {$length} but it should be {$expected_length}"); } $colors = [DC::decode(Base83::decode(substr($blurhash, 2, 4)))]; $quant_max_ac_component = Base83::decode($blurhash[1]); $max_value = ($quant_max_ac_component + 1) / 166; for ($i = 1; $i < $size_x * $size_y; $i++) { $value = Base83::decode(substr($blurhash, 4 + $i * 2, 2)); $colors[$i] = AC::decode($value, $max_value * $punch); } $pixels = []; for ($y = 0; $y < $height; $y++) { $row = []; for ($x = 0; $x < $width; $x++) { $r = $g = $b = 0; for ($j = 0; $j < $size_y; $j++) { for ($i = 0; $i < $size_x; $i++) { $color = $colors[$i + $j * $size_x]; $basis = cos((M_PI * $x * $i) / $width) * cos((M_PI * $y * $j) / $height); $r += $color[0] * $basis; $g += $color[1] * $basis; $b += $color[2] * $basis; } } $row[] = $linear ? [$r, $g, $b] : [ Color::toSRGB($r), Color::toSRGB($g), Color::toSRGB($b) ]; } $pixels[] = $row; } return $pixels; } }