php 62 lines · 10 steps

Batch image resizing with PHP GD

A service that scales every image in a directory to fit within bounds while preserving type and transparency.

Explained by highlit

Intermediate image-processing constructor-promotion match-expression gd-library aspect-ratio

1<?php
2 
3namespace App\Services;
4 
5use RuntimeException;
6 
7final class ImageResizer
8{
9    public function __construct(
10        private readonly int $maxWidth = 1920,
11        private readonly int $maxHeight = 1080,
12        private readonly int $jpegQuality = 82,
13    ) {}
14 
15    public function resizeDirectory(string $sourceDir, string $targetDir): array
16    {
17        if (!is_dir($targetDir) && !mkdir($targetDir, 0755, true) && !is_dir($targetDir)) {
18            throw new RuntimeException("Cannot create target directory: {$targetDir}");
19        }
20 
21        $processed = [];
22        foreach (glob(rtrim($sourceDir, '/') . '/*.{jpg,jpeg,png}', GLOB_BRACE) as $path) {
23            $target = $targetDir . '/' . basename($path);
24            $this->resize($path, $target);
25            $processed[] = $target;
26        }
27 
28        return $processed;
29    }
30 
31    public function resize(string $source, string $target): void
32    {
33        [$width, $height, $type] = getimagesize($source) ?: throw new RuntimeException("Not an image: {$source}");
34 
35        $src = match ($type) {
36            IMAGETYPE_JPEG => imagecreatefromjpeg($source),
37            IMAGETYPE_PNG => imagecreatefrompng($source),
38            default => throw new RuntimeException("Unsupported type: {$source}"),
39        };
40 
41        $scale = min($this->maxWidth / $width, $this->maxHeight / $height, 1.0);
42        $newWidth = max(1, (int) round($width * $scale));
43        $newHeight = max(1, (int) round($height * $scale));
44 
45        $dst = imagecreatetruecolor($newWidth, $newHeight);
46 
47        if ($type === IMAGETYPE_PNG) {
48            imagealphablending($dst, false);
49            imagesavealpha($dst, true);
50        }
51 
52        imagecopyresampled($dst, $src, 0, 0, 0, 0, $newWidth, $newHeight, $width, $height);
53 
54        match ($type) {
55            IMAGETYPE_JPEG => imagejpeg($dst, $target, $this->jpegQuality),
56            IMAGETYPE_PNG => imagepng($dst, $target, 6),
57        };
58 
59        imagedestroy($src);
60        imagedestroy($dst);
61    }
62}

01 / 01

STEP 01

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Three takeaways

1Constructor property promotion with readonly gives you immutable, self-documenting configuration in one signature.
2Scaling by the minimum ratio capped at 1.0 fits an image inside a box without ever enlarging it.
3GD handles are raw resources, so freeing them with imagedestroy is essential to avoid leaking memory.

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