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<?php |
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declare(strict_types=1); |
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namespace Phpml\Dataset; |
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use Phpml\Exception\InvalidArgumentException; |
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/** |
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* MNIST dataset: http://yann.lecun.com/exdb/mnist/ |
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* original mnist dataset reader: https://github.com/AndrewCarterUK/mnist-neural-network-plain-php |
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*/ |
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final class MnistDataset extends ArrayDataset |
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{ |
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private const MAGIC_IMAGE = 0x00000803; |
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private const MAGIC_LABEL = 0x00000801; |
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private const IMAGE_ROWS = 28; |
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private const IMAGE_COLS = 28; |
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public function __construct(string $imagePath, string $labelPath) |
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{ |
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$this->samples = $this->readImages($imagePath); |
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$this->targets = $this->readLabels($labelPath); |
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if (count($this->samples) !== count($this->targets)) { |
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throw new InvalidArgumentException('Must have the same number of images and labels'); |
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} |
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} |
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private function readImages(string $imagePath): array |
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{ |
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$stream = fopen($imagePath, 'rb'); |
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if ($stream === false) { |
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throw new InvalidArgumentException('Could not open file: '.$imagePath); |
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} |
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$images = []; |
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try { |
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$header = fread($stream, 16); |
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$fields = unpack('Nmagic/Nsize/Nrows/Ncols', (string) $header); |
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if ($fields['magic'] !== self::MAGIC_IMAGE) { |
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throw new InvalidArgumentException('Invalid magic number: '.$imagePath); |
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} |
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if ($fields['rows'] != self::IMAGE_ROWS) { |
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throw new InvalidArgumentException('Invalid number of image rows: '.$imagePath); |
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} |
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if ($fields['cols'] != self::IMAGE_COLS) { |
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throw new InvalidArgumentException('Invalid number of image cols: '.$imagePath); |
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} |
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for ($i = 0; $i < $fields['size']; $i++) { |
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$imageBytes = fread($stream, $fields['rows'] * $fields['cols']); |
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// Convert to float between 0 and 1 |
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$images[] = array_map(function ($b) { |
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return $b / 255; |
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}, array_values(unpack('C*', (string) $imageBytes))); |
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} |
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} finally { |
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fclose($stream); |
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} |
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return $images; |
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} |
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private function readLabels(string $labelPath): array |
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{ |
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$stream = fopen($labelPath, 'rb'); |
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if ($stream === false) { |
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throw new InvalidArgumentException('Could not open file: '.$labelPath); |
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} |
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$labels = []; |
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try { |
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$header = fread($stream, 8); |
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$fields = unpack('Nmagic/Nsize', (string) $header); |
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if ($fields['magic'] !== self::MAGIC_LABEL) { |
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throw new InvalidArgumentException('Invalid magic number: '.$labelPath); |
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} |
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$labels = fread($stream, $fields['size']); |
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} finally { |
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fclose($stream); |
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} |
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return array_values(unpack('C*', (string) $labels)); |
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} |
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} |
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