First Commit

vendor/php-ai/php-ml/src/Dataset/MnistDataset.php

@@ -0,0 +1,101 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phpml\Dataset;
+
+use Phpml\Exception\InvalidArgumentException;
+
+/**
+ * MNIST dataset: http://yann.lecun.com/exdb/mnist/
+ * original mnist dataset reader: https://github.com/AndrewCarterUK/mnist-neural-network-plain-php
+ */
+final class MnistDataset extends ArrayDataset
+{
+    private const MAGIC_IMAGE = 0x00000803;
+
+    private const MAGIC_LABEL = 0x00000801;
+
+    private const IMAGE_ROWS = 28;
+
+    private const IMAGE_COLS = 28;
+
+    public function __construct(string $imagePath, string $labelPath)
+    {
+        $this->samples = $this->readImages($imagePath);
+        $this->targets = $this->readLabels($labelPath);
+
+        if (count($this->samples) !== count($this->targets)) {
+            throw new InvalidArgumentException('Must have the same number of images and labels');
+        }
+    }
+
+    private function readImages(string $imagePath): array
+    {
+        $stream = fopen($imagePath, 'rb');
+
+        if ($stream === false) {
+            throw new InvalidArgumentException('Could not open file: '.$imagePath);
+        }
+
+        $images = [];
+
+        try {
+            $header = fread($stream, 16);
+
+            $fields = unpack('Nmagic/Nsize/Nrows/Ncols', (string) $header);
+
+            if ($fields['magic'] !== self::MAGIC_IMAGE) {
+                throw new InvalidArgumentException('Invalid magic number: '.$imagePath);
+            }
+
+            if ($fields['rows'] != self::IMAGE_ROWS) {
+                throw new InvalidArgumentException('Invalid number of image rows: '.$imagePath);
+            }
+
+            if ($fields['cols'] != self::IMAGE_COLS) {
+                throw new InvalidArgumentException('Invalid number of image cols: '.$imagePath);
+            }
+
+            for ($i = 0; $i < $fields['size']; $i++) {
+                $imageBytes = fread($stream, $fields['rows'] * $fields['cols']);
+
+                // Convert to float between 0 and 1
+                $images[] = array_map(function ($b) {
+                    return $b / 255;
+                }, array_values(unpack('C*', (string) $imageBytes)));
+            }
+        } finally {
+            fclose($stream);
+        }
+
+        return $images;
+    }
+
+    private function readLabels(string $labelPath): array
+    {
+        $stream = fopen($labelPath, 'rb');
+
+        if ($stream === false) {
+            throw new InvalidArgumentException('Could not open file: '.$labelPath);
+        }
+
+        $labels = [];
+
+        try {
+            $header = fread($stream, 8);
+
+            $fields = unpack('Nmagic/Nsize', (string) $header);
+
+            if ($fields['magic'] !== self::MAGIC_LABEL) {
+                throw new InvalidArgumentException('Invalid magic number: '.$labelPath);
+            }
+
+            $labels = fread($stream, $fields['size']);
+        } finally {
+            fclose($stream);
+        }
+
+        return array_values(unpack('C*', (string) $labels));
+    }
+}