Opal

High-performance image processing for PHP, backed by libvips

Features

• Lazy Evaluation: All image operations are lazy and only executed when needed (saving, encoding, exporting)
• Immutable Operations: Every transformation returns a new image instance
• NDArray Integration: Seamless interoperability with phpmlkit/ndarray for ML workflows
• Comprehensive API: Support for all common image operations
• Type-Safe: Full PHP 8.2+ type safety with enums and value objects
• Memory Efficient: Zero-copy operations where possible

Performance

Load → resize → rotate 45° → sharpen (full pipeline):

Image	GD	Imagick	Opal
640×480	8.48 ms	128.55 ms	1.56 ms
1920×1080	49.67 ms	721.97 ms	5.36 ms
4000×2670	152.74 ms	2,039.15 ms	15.47 ms
6000×4000	299.43 ms	3,538.47 ms	33.17 ms

Apple M1, macOS. Run: php benchmarks/opal-vs-gd-vs-imagick.php

Installation

composer require phpmlkit/opal

Quick Start

use PhpMlKit\Opal\Image;
use PhpMlKit\Opal\Color;
use PhpMlKit\Opal\ColorSpace;
use PhpMlKit\Opal\Kernel;

// Load an image
$image = Image::fromFile('path/to/image.jpg');

// Resize with high-quality kernel
$resized = $image->resize(800, 600, Kernel::Lanczos3);

// Convert to grayscale
$grayscale = $resized->toGrayscale();

// Save the result
$grayscale->toFile('output.jpg');

Core Concepts

Lazy Evaluation

All image operations are lazy - they build a pipeline that's only executed when you call a terminal operation:

// This doesn't process anything yet
$pipeline = $image
    ->resize(800, 600)
    ->toGrayscale()
    ->brightness(1.2);

// This triggers the actual processing
$pipeline->toFile('output.jpg');

Immutable Operations

Every transformation returns a new image instance:

$original = Image::fromFile('input.jpg');
$modified = $original->resize(800, 600);

// $original is unchanged
$original->toFile('original.jpg');
$modified->toFile('resized.jpg');

Usage Examples

Basic Image Operations

use PhpMlKit\Opal\Image;
use PhpMlKit\Opal\Color;
use PhpMlKit\Opal\ColorSpace;
use PhpMlKit\Opal\Kernel;
use PhpMlKit\Opal\FlipDirection;

// Load image
$image = Image::fromFile('photo.jpg');

// Resize
$resized = $image->resize(1920, 1080);
$scaled = $image->scale(0.5);

// Thumbnail via shrink-on-load — faster than load+resize
$thumbnail = Image::thumbnail('photo.jpg', 300);

// Crop
$cropped = $image->crop(100, 100, 800, 600);
$centerCropped = $image->centerCrop(800, 600);

// Flip and rotate
$flipped = $image->flip(FlipDirection::Horizontal);
$rotated = $image->rotate(45);
$rotated90 = $image->rot90();

// Save
$resized->toFile('resized.jpg');

Color Space Conversion

use PhpMlKit\Opal\Image;
use PhpMlKit\Opal\ColorSpace;

$image = Image::fromFile('photo.jpg');

// Convert to grayscale
$grayscale = $image->toGrayscale();

// Convert to RGB
$rgb = $grayscale->toRGB();

// Add alpha channel
$rgba = $image->toRGBA();

// Remove alpha
$rgb = $rgba->removeAlpha();

Color Adjustments

use PhpMlKit\Opal\Image;

$image = Image::fromFile('photo.jpg');

// Brightness (1.0 = unchanged, >1 = brighter, <1 = darker)
$brighter = $image->brightness(1.2);

// Contrast (1.0 = unchanged, >1 = more contrast, <1 = less contrast)
$highContrast = $image->contrast(1.5);

// Saturation (0 = grayscale, 1.0 = unchanged, >1 = more saturated)
$vivid = $image->saturation(1.3);

// Hue rotation
$hueShifted = $image->hue(90);

// Gamma correction
$gammaCorrected = $image->gamma(2.2);

Filters and Effects

use PhpMlKit\Opal\Image;

$image = Image::fromFile('photo.jpg');

// Sharpen
$sharpened = $image->sharpen(sigma: 2.0);

// Blur
$blurred = $image->blur(sigma: 3.0);

// Median blur (good for noise reduction)
$denoised = $image->medianBlur(5);

// Invert colors
$inverted = $image->invert();

Drawing and Compositing

use PhpMlKit\Opal\Image;
use PhpMlKit\Opal\Color;
use PhpMlKit\Opal\BoundingBox;

$image = Image::fromFile('photo.jpg');

// Draw rectangle
$withRect = $image->drawRect(
    100, 100, 200, 150,
    Color::red()
);

// Draw circle
$withCircle = $image->drawCircle(
    400, 300, 50,
    Color::blue(),
    fill: true
);

// Draw text
$withText = $image->drawText(
    'Hello World',
    100, 100,
    color: Color::white()
);

// Composite images
$overlay = Image::fromFile('overlay.png');
$composited = $image->composite($overlay, 50, 50);

NDArray Interoperability

use PhpMlKit\Opal\Image;
use PhpMlKit\NDArray\NDArray;
use PhpMlKit\Opal\ColorSpace;
use PhpMlKit\Opal\ChannelFormat;

// Convert image to NDArray
$image = Image::fromFile('photo.jpg');
$array = $image->toArray(ChannelFormat::HWC);  // [H, W, C]

// Convert NDArray to image
$array = NDArray::zeros([224, 224, 3]);
$image = Image::fromArray($array, ColorSpace::RGB, ChannelFormat::HWC);

Advanced Options

use PhpMlKit\Opal\Image;
use PhpMlKit\Opal\LoadOptions;
use PhpMlKit\Opal\SaveOptions;

// Load with options
$image = Image::fromFile('photo.jpg', LoadOptions::default()
    ->withAutoRotate(true)
    ->withShrink(2)
);

// Save with options
$image->toFile('output.jpg', SaveOptions::jpeg(
    quality: 90,
    strip: true,
    progressive: true
));

// PNG with compression
$image->toFile('output.png', SaveOptions::png(
    compression: 9,
    interlace: true
));

// WebP with lossless
$image->toFile('output.webp', SaveOptions::webp(
    quality: 80,
    lossless: false
));

API Reference

Value Objects

Color

Immutable RGBA color representation.

$red = Color::rgb(255, 0, 0);
$blue = Color::fromHex('#0000ff');
$white = Color::white();
$transparent = Color::transparent();

ImageSize

Immutable 2D size descriptor.

$size = new ImageSize(1920, 1080);
$aspectRatio = $size->aspectRatio();
$pixels = $size->pixels();

BoundingBox

Immutable axis-aligned bounding box.

$box = new BoundingBox(10, 10, 100, 50);
$iou = $box->iou($otherBox);
$clamped = $box->clamp($imageWidth, $imageHeight);

Enums

• ColorSpace: RGB, RGBA, BGR, BGRA, Grayscale, Lab, HSV, CMYK
• ImageFormat: JPEG, PNG, WebP, TIFF, GIF, BMP, AVIF, HEIF
• Kernel: Nearest, Linear, Cubic, Mitchell, Lanczos2, Lanczos3, Mks211, Mks213
• FlipDirection: Horizontal, Vertical, Both
• BandFormat: UChar, UInt16, Float, Double
• ChannelFormat: HWC, CHW

Options Classes

LoadOptions

Control image loading behavior.

$options = LoadOptions::default()
    ->withPage(0)
    ->withAutoRotate(true)
    ->withShrink(2);

SaveOptions

Control image saving behavior.

$options = SaveOptions::jpeg(quality: 90, strip: true);
$options = SaveOptions::png(compression: 9);
$options = SaveOptions::webp(quality: 80, lossless: false);

Performance Tips

1. Use lazy evaluation: Chain operations together before saving
2. Use shrink-on-load: Load with Image::thumbnail() or LoadOptions::withShrink() for large images
3. Choose appropriate interpolation: Use Lanczos for quality, Bilinear for speed
4. Dispose explicitly: Call dispose() when done with large images

Documentation

• Full Documentation
• What is Opal?
• Quick Start
• API Reference
• Installation

Development

# Install dependencies
composer install

# Run tests
composer test

# Run static analysis
composer lint

# Format code
composer cs:fix

Requirements

• PHP 8.2 or higher
• ext-ffi extension

License

MIT

Credits

• libvips — image processing engine
• jcupitt/vips — PHP FFI bindings for libvips
• phpmlkit/ndarray — numerical computing for ML workflows