Resizing Images

The resizeImage method is one of the core features of the Imagick Image Processor library. It allows you to resize images while automatically maintaining their aspect ratio.

Basic Usage

use Kenura\Imagick\ImageProcessor;

$processor = new ImageProcessor();

$processor->resizeImage(
    'path/to/input.jpg',    // Input image path
    'path/to/output.jpg',   // Output image path
    800,                     // Target width
    600                      // Target height
);

How Aspect Ratio Preservation Works

The library automatically calculates the best dimensions to maintain your image’s aspect ratio:

// Original image: 1920x1080 (16:9 ratio)
// Requested: 800x600

// Result: 800x450 (maintains 16:9 ratio)
$processor->resizeImage('wide.jpg', 'resized.jpg', 800, 600);

// Original image: 1080x1920 (9:16 ratio - portrait)
// Requested: 800x600

// Result: 337x600 (maintains 9:16 ratio)
$processor->resizeImage('tall.jpg', 'resized.jpg', 800, 600);

Common Resize Scenarios

1. Thumbnail Generation

Create small thumbnails for galleries:

$processor = new ImageProcessor();

// Create 150x150 thumbnail (actual size depends on aspect ratio)
$processor->resizeImage(
    'photos/original.jpg',
    'thumbnails/thumb.jpg',
    150,
    150
);

2. Web Optimization

Resize images for web display:

// Standard web size
$processor->resizeImage('large.jpg', 'web.jpg', 1200, 800);

// Mobile-friendly size
$processor->resizeImage('large.jpg', 'mobile.jpg', 600, 400);

// Retina display (2x)
$processor->resizeImage('large.jpg', 'retina.jpg', 2400, 1600);

Prepare images for different social media platforms:

$processor = new ImageProcessor();

// Instagram post (1:1)
$processor->resizeImage('photo.jpg', 'instagram.jpg', 1080, 1080);

// Facebook cover (820:312 ratio)
$processor->resizeImage('cover.jpg', 'fb-cover.jpg', 820, 312);

// Twitter header (1500:500 ratio)
$processor->resizeImage('header.jpg', 'twitter.jpg', 1500, 500);

// YouTube thumbnail (1280:720 ratio)
$processor->resizeImage('video-thumb.jpg', 'youtube.jpg', 1280, 720);

Batch Resizing

Process multiple images at once:

<?php

require_once __DIR__ . '/vendor/autoload.php';

use Kenura\Imagick\ImageProcessor;

$processor = new ImageProcessor();

// Configuration
$inputDir = 'originals/';
$outputDir = 'resized/';
$targetWidth = 1200;
$targetHeight = 800;

// Create output directory if it doesn't exist
if (!is_dir($outputDir)) {
    mkdir($outputDir, 0755, true);
}

// Get all images
$images = glob($inputDir . '*.{jpg,jpeg,png,gif}', GLOB_BRACE);

foreach ($images as $image) {
    $filename = basename($image);
    $outputPath = $outputDir . $filename;

    try {
        $processor->resizeImage($image, $outputPath, $targetWidth, $targetHeight);
        echo "✅ Resized: $filename\n";
    } catch (Exception $e) {
        echo "❌ Error resizing $filename: " . $e->getMessage() . "\n";
    }
}

echo "Batch processing complete!";

Responsive Image Sets

Create multiple sizes for responsive images:

<?php

require_once __DIR__ . '/vendor/autoload.php';

use Kenura\Imagick\ImageProcessor;

$processor = new ImageProcessor();

$inputImage = 'original.jpg';
$sizes = [
    'small' => [480, 320],
    'medium' => [768, 512],
    'large' => [1200, 800],
    'xlarge' => [1920, 1280]
];

foreach ($sizes as $name => $dimensions) {
    list($width, $height) = $dimensions;
    $outputPath = "responsive/{$name}.jpg";

    $processor->resizeImage($inputImage, $outputPath, $width, $height);
    echo "Created {$name} version: {$width}x{$height}\n";
}

Then use in HTML:

<picture>
    <source media="(min-width: 1200px)" srcset="responsive/xlarge.jpg">
    <source media="(min-width: 768px)" srcset="responsive/large.jpg">
    <source media="(min-width: 480px)" srcset="responsive/medium.jpg">
    <img src="responsive/small.jpg" alt="Responsive image">
</picture>

Preserving Image Quality

The resizeImage method uses high-quality resampling:

// The library uses imagescale() which provides high-quality results
// No additional quality parameters needed for resizing
$processor->resizeImage('input.jpg', 'output.jpg', 800, 600);

// For quality control during compression, use compressToJpg() after resizing
$processor->resizeImage('input.jpg', 'temp.jpg', 800, 600);
$processor->compressToJpg('temp.jpg', 'output.jpg', 150); // 150KB target
unlink('temp.jpg');

Working with Different Formats

JPEG Images

// Standard JPEG resize
$processor->resizeImage('photo.jpg', 'resized.jpg', 1024, 768);

PNG Images

// PNG with transparency preserved
$processor->resizeImage('logo.png', 'resized-logo.png', 400, 300);

GIF Images

// GIF (first frame only)
$processor->resizeImage('animation.gif', 'resized.gif', 600, 400);

Error Handling

Always handle potential errors:

<?php

require_once __DIR__ . '/vendor/autoload.php';

use Kenura\Imagick\ImageProcessor;

$processor = new ImageProcessor();

try {
    // Check if input file exists
    $inputPath = 'photos/original.jpg';
    if (!file_exists($inputPath)) {
        throw new Exception("Input file not found: $inputPath");
    }

    // Check if input is a valid image
    $imageInfo = getimagesize($inputPath);
    if ($imageInfo === false) {
        throw new Exception("Invalid image file: $inputPath");
    }

    // Perform resize
    $processor->resizeImage($inputPath, 'output.jpg', 800, 600);

    echo "Image resized successfully!";

} catch (Exception $e) {
    error_log("Resize error: " . $e->getMessage());
    echo "Failed to resize image. Please try again.";
}

Performance Tips

1. Don’t Upscale

Avoid making images larger than their original size:

// Get original dimensions
list($origWidth, $origHeight) = getimagesize('input.jpg');

// Only resize if larger than target
$targetWidth = 1200;
$targetHeight = 800;

if ($origWidth > $targetWidth || $origHeight > $targetHeight) {
    $processor->resizeImage('input.jpg', 'output.jpg', $targetWidth, $targetHeight);
} else {
    // Just copy the file
    copy('input.jpg', 'output.jpg');
}

2. Process in Background

For large batches, use background processing:

// Example using a simple queue
$queue = [
    ['input' => 'img1.jpg', 'output' => 'out1.jpg', 'width' => 800, 'height' => 600],
    ['input' => 'img2.jpg', 'output' => 'out2.jpg', 'width' => 800, 'height' => 600],
    // ... more images
];

foreach ($queue as $job) {
    $processor->resizeImage(
        $job['input'],
        $job['output'],
        $job['width'],
        $job['height']
    );
}

3. Clean Up Temporary Files

Always remove temporary files:

$tempFile = 'temp_' . uniqid() . '.jpg';

try {
    $processor->resizeImage('input.jpg', $tempFile, 800, 600);
    // ... do something with $tempFile
} finally {
    if (file_exists($tempFile)) {
        unlink($tempFile);
    }
}

Method Signature

public function resizeImage(
    string $inputImagePath,   // Path to input image
    string $outputImagePath,  // Path to save resized image
    int $width,               // Target width in pixels
    int $height               // Target height in pixels
): void