regioned-image

Breaks an image into regions of contiguous pixels. You can set the colors and boundaries of regioned images and render them to a canvas.

Setup

Install the package.

npm install regioned-image --save

Require the module.

var RegionedImage = require("regioned-image");

Note: RegionedImage needs to run a browser context. You can use something like browserify to bundle RegionedImage as a dependency. Take a look at the example if you need help with this.

Usage

<canvas id="canvas"></canvas>

<script>
  var image = new RegionedImage("france.svg");
  image.onload = function () {

    // Print the dimensions of the image.
    console.log(image.width);  // 600
    console.log(image.height); // 400

    // Build the regions for the flag of france.
    image.buildRegion({ x: 100, y: 10 }); // Blue
    image.buildRegion({ x: 300, y: 10 }); // White
    image.buildRegion({ x: 500, y: 10 }); // Red

    // Get the blue region from the 'regions' property.
    var blueRegion = image.regions[0];

    // Print the number of pixels in the region.
    console.log(blueRegion.size); // 80000

    // Print the original color of the region.
    console.log(blueRegion.originalColor); // #0055A4

    // Print whether the region contains a cell.
    console.log(blueRegion.contains({ x: 90, y: 20 })); // true

    // Set the region's color to yellow.
    blueRegion.color = "#FFFF00";

    // Set the region's boundary color to green.
    blueRegion.boundaryColor = "#00FF00";

    // Get the red region by specifying a pixel inside the region.
    var redRegion = image.regionAt({ x: 490, y: 20 });

    // Merge the red region into the blue region.
    blueRegion.merge(redRegion);

    // Print the number of pixels in the blue and red regions.
    console.log(blueRegion.size); // 160000
    console.log(redRegion.size);  // 0

    // Print the number of regions in the regioned image.
    console.log(image.regions.length); // 2

    // Render the image to the canvas.
    var canvas = document.getElementById("canvas");
    image.render(canvas);
  };
</script>

You can specify a different width and height for the image at initialization:

var image = new RegionedImage("france.svg", {
  width: 300,
  height: 200
});

The aspect ratio of the image will be preserved. This means that the image may be smaller than the width and height specified.

Serialization

Once the image has loaded, you can serialize your regioned image to json:

var image = new RegionedImage("france.svg");
var json;

image.onload = function () {
  image.buildRegion({ x: 100, y: 10 });
  json = image.toJson();
};

var clone = RegionedImage.fromJson(json);
console.log(clone.regions.length); // 1

Touch events

You can register a touch listener for the regioned image. It will be given the relative coordinates of the touch:

var image = new RegionedImage("france.svg");
var canvas = document.getElementById("canvas");

image.onload = function () {
  image.render(canvas);
};

image.ontouch = function (x, y) {
  var region = image.buildRegion({ x: x, y: y });
  region.color = "#FFFF00";
  image.render(canvas);
};

Reset

You can reset all region colors and boundary colors with the #reset method.

Note: If regions of different colors have been merged, it will reset to the original color of the merging region, which may not be the same as the original image.

## Screenshot

Contribution

Please send a pull request or open an issue.

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