Lume

High-performance image manipulation for Flutter, powered by Rust.

Lume provides a fluent, chainable API for image processing through Rust's image and imageproc libraries via Flutter Rust Bridge.

Overview

Two main interfaces:

LumeImage — Basic operations: resize, crop, rotate, color adjustments, format conversion.
LumeCanvas — Advanced processing: edge detection, filters, morphology, computer vision, drawing.

import 'package:lume/lume.dart';

// Basic: load, resize, convert to grayscale
final img = LumeImage.fromFile(file)
  .resize(width: 800, height: 600)
  .grayscale()
  .toPng();

// Advanced: Canny edge detection + drawing
final processed = LumeCanvas(img)
  .canny(low: 50, high: 150)
  .drawFilledCircle(cx: 100, cy: 100, radius: 30, color: Colors.red)
  .toLumeImage();

// Use in Flutter widgets
LumeImageWidget(image: processed, fit: BoxFit.cover);

Installation

Add to pubspec.yaml:

dependencies:
  lume:
    path: ./lume # or from pub.dev when published

Run:

flutter pub get

LumeImage — Basic Operations

Factories

Method	Description
`LumeImage.fromBytes(Uint8List bytes)`	From raw encoded bytes (PNG, JPEG, WebP, etc.)
`LumeImage.fromFile(File file)`	From file (sync)
`LumeImage.fromFileAsync(File file)`	From file (async)
`LumeImage.fromPath(String path)`	From path string (sync)
`LumeImage.fromPathAsync(String path)`	From path string (async)
`LumeImage.fromAsset(String assetPath)`	From Flutter asset
`LumeImage.blank({width, height, r, g, b, a})`	Create blank image
`LumeImage.from(LumeImage other)`	Copy constructor

Accessors

Uint8List bytes = img.bytes;    // Raw encoded bytes
int width = img.width;          // Image width
int height = img.height;        // Image height
String format = img.format;     // Format (png, jpeg, etc.)
int size = img.sizeBytes;       // Size in bytes
LumeImageInfo info = img.info;  // Full metadata

Transform Operations

// Resize
img.resize(width: 800, height: 600, keepAspectRatio: true);
img.resizeWithFilter(width: 800, height: 600, filter: 'lanczos3');
img.thumbnail(maxWidth: 300, maxHeight: 300);
img.thumbnailExact(width: 200, height: 200);

// Crop
img.crop(x: 100, y: 100, width: 400, height: 400);

// Rotate & Flip
img.rotate(degrees: 90);   // 90, 180, 270
img.flipHorizontal();
img.flipVertical();

// Compose
img.overlay(otherImage, x: 50, y: 50);
img.tile(cols: 3, rows: 2);

Color Operations

img.grayscale();
img.adjustBrightness(30);      // Positive = brighter
img.adjustContrast(0.5);       // >0 = more contrast
img.blur(sigma: 2.0);
img.sharpen(sigma: 1.0, threshold: 10);
img.invertColors();
img.hueRotate(degrees: 45);

Format Conversion

img.convertFormat('png');
img.toPng();
img.toJpeg();
img.toWebp();

Persistence

// Async
await img.writeToFile(file);
await img.saveTo('/path/to/output.png');

// Sync
img.writeToFileSync(file);
img.saveToSync('/path/to/output.png');

LumeCanvas — Advanced Processing

Filters

LumeCanvas(img)
  .gaussianBlur(sigma: 2.0)
  .medianFilter(xRadius: 2, yRadius: 2)
  .bilateralFilter(windowSize: 5, sigmaColor: 10.0, sigmaSpatial: 10.0)
  .boxFilter(xRadius: 3, yRadius: 3)
  .sharpen3x3()
  .sharpenGaussian(sigma: 1.0, amount: 2.0)
  .laplacianFilter()
  .toLumeImage();

Edge Detection

LumeCanvas(img)
  .canny(low: 50, high: 150)      // Canny edge detector
  .sobelGradients()                // Sobel gradients
  .toLumeImage();

Contrast & Threshold

LumeCanvas(img)
  .adaptiveThreshold(blockRadius: 5)
  .otsuThreshold()
  .threshold(value: 128, invert: false)
  .equalizeHistogram()
  .stretchContrast(
    inputLower: 50,
    inputUpper: 200,
    outputLower: 0,
    outputUpper: 255,
  )
  .toLumeImage();

Morphology

LumeCanvas(img)
  .dilate(radius: 2)               // Expand white regions
  .erode(radius: 2)                // Shrink white regions
  .morphologicalOpen(radius: 3)    // Erode then dilate
  .morphologicalClose(radius: 3)   // Dilate then erode
  .toLumeImage();

Geometric Transformations

LumeCanvas(img)
  .rotateAboutCenter(theta: 0.5, backgroundColor: Colors.black)
  .translate(tx: 50, ty: -30)
  .toLumeImage();

Noise

LumeCanvas(img)
  .gaussianNoise(mean: 0.0, stddev: 20.0, seed: BigInt.from(42))
  .saltAndPepperNoise(rate: 0.05, seed: BigInt.from(123))
  .toLumeImage();

Seam Carving

// Content-aware width reduction
LumeCanvas(img).seamCarveWidth(newWidth: 400).toLumeImage();

Drawing

LumeCanvas(img)
  // Lines
  .drawLine(x1: 0, y1: 0, x2: 100, y2: 100, color: Colors.red)
  .drawAntialiasedLine(x1: 0, y1: 0, x2: 100, y2: 100, color: Colors.blue)

  // Rectangles
  .drawHollowRect(x: 10, y: 10, width: 100, height: 50, color: Colors.green)
  .drawFilledRect(x: 10, y: 10, width: 100, height: 50, color: Colors.yellow)

  // Circles
  .drawHollowCircle(cx: 100, cy: 100, radius: 50, color: Colors.purple)
  .drawFilledCircle(cx: 100, cy: 100, radius: 50, color: Colors.orange)

  // Ellipses
  .drawHollowEllipse(cx: 100, cy: 100, widthRadius: 80, heightRadius: 40, color: Colors.cyan)
  .drawFilledEllipse(cx: 100, cy: 100, widthRadius: 80, heightRadius: 40, color: Colors.pink)

  // Polygons
  .drawFilledPolygon(points: [(0, 0), (100, 0), (50, 100)], color: Colors.teal)
  .drawHollowPolygon(points: [(0, 0), (100, 0), (50, 100)], color: Colors.indigo)

  // Curves
  .drawCubicBezier(
    startX: 0, startY: 0,
    endX: 200, endY: 200,
    ctrl1X: 50, ctrl1Y: 100,
    ctrl2X: 150, ctrl2Y: 50,
    color: Colors.brown,
  )

  // Markers
  .drawCross(cx: 100, cy: 100, color: Colors.white)

  .toLumeImage();

Computer Vision / Analysis

// Find contours
List<LumeContour> contours = LumeCanvas(binaryImg).findContours();

// Distance transform
LumeImage distance = LumeCanvas(img).distanceTransform().toLumeImage();

Flutter Integration

LumeImageProvider

Use LumeImage with any Flutter widget that accepts an ImageProvider:

Image(image: LumeImageProvider(myLumeImage));
DecorationImage(image: LumeImageProvider(myLumeImage), fit: BoxFit.cover);
CircleAvatar(backgroundImage: LumeImageProvider(myLumeImage));

LumeImageWidget

Convenience widget with common Image parameters:

LumeImageWidget(
  image: myLumeImage,
  fit: BoxFit.cover,
  width: 300,
  height: 200,
);

Chainable API

Both LumeImage and LumeCanvas are immutable — each operation returns a new instance:

// Branch pipelines freely
final original = LumeImage.fromFile(file);

final small = original.thumbnail(maxWidth: 100, maxHeight: 100);
final grayscale = original.grayscale();
final edges = LumeCanvas(original).canny(low: 50, high: 150).toLumeImage();

// Original is unchanged