64 lines
1.5 KiB
PHP
64 lines
1.5 KiB
PHP
<?php
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namespace Image\PerceptualHash\Algorithm;
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use LengthException;
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use Image\PerceptualHash\Algorithm;
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class AverageHash implements Algorithm
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{
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const SIZE = 8;
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/**
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* {@inheritDoc}
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*/
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public function bin($resource)
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{
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// Resize
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$resized = imagecreatetruecolor(static::SIZE, static::SIZE);
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imagecopyresampled(
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$resized, $resource, 0, 0, 0, 0,
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static::SIZE, static::SIZE, imagesx($resource), imagesy($resource));
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// Create an array of gray-scaled pixel values.
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$pixels = array();
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for ($y = 0; $y < static::SIZE; $y++) {
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for ($x = 0; $x < static::SIZE; $x++) {
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$rgb = imagecolorsforindex($resized, imagecolorat($resized, $x, $y));
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$pixels[] = ($rgb['red'] + $rgb['green'] + $rgb['blue']) / 3;
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}
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}
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imagedestroy($resized);
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// Calculate a mean of gray-scaled pixel value.
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$mean = array_sum($pixels) / count($pixels);
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$bin = '';
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$one = 1;
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foreach ($pixels as $pixel) {
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$bin .= $pixel > $mean ? 1 : 0;
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$one = $one << 1;
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}
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return $bin;
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}
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/**
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* {@inheritDoc}
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*/
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public function hex($bin)
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{
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if (strlen($bin) !== self::SIZE * self::SIZE) {
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throw new LengthException('Binary length must be ' . self::SIZE * self::SIZE);
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}
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$hex = '';
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foreach (str_split($bin, 4) as $bin) {
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$hex .= dechex(bindec($bin));
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}
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return $hex;
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}
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}
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