🎉 Add initial implementation

.gitignore

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+/.nyc_output/
+/node_modules/

browser.js

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+/* eslint-env browser */
+
+module.exports = ImageData

index.d.ts

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+declare class ImageData {
+  /**
+   * Creates an `ImageData` object from a given `Uint8ClampedArray` and the size of the image it contains.
+   *
+   * @param array A `Uint8ClampedArray` containing the underlying pixel representation of the image.
+   * @param width An `unsigned` `long` representing the width of the image.
+   * @param height An `unsigned` `long` representing the height of the image. This value is optional: the height will be inferred from the array's size and the given width.
+   */
+  constructor (array: Uint8ClampedArray, width: number, height?: number)
+
+  /**
+   * Creates an `ImageData` object of a black rectangle with the given width and height.
+   *
+   * @param width An `unsigned` `long` representing the width of the image.
+   * @param height An `unsigned` `long` representing the height of the image.
+   */
+  constructor (width: number, height: number)
+
+  /**
+   * A `Uint8ClampedArray` representing a one-dimensional array containing the data in the RGBA order, with integer values between `0` and `255` (included).
+   */
+  readonly data: Uint8ClampedArray
+
+  /**
+   * An `unsigned` `long` representing the actual height, in pixels, of the `ImageData`.
+   */
+  readonly height: number
+
+  /**
+   * An `unsigned` `long` representing the actual width, in pixels, of the `ImageData`.
+   */
+  readonly width: number
+}
+
+export = ImageData

index.js

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+const widthMap = new WeakMap()
+const heightMap = new WeakMap()
+
+class ImageData {
+  constructor (width, height, ...args) {
+    if (arguments.length < 2) {
+      throw new TypeError(`Failed to construct 'ImageData': 2 arguments required, but only ${arguments.length} present.`)
+    }
+
+    if (typeof width === 'object') {
+      if (!(width instanceof Uint8ClampedArray)) {
+        throw new TypeError(`Failed to construct 'ImageData': parameter 1 is not of type 'Uint8ClampedArray'.`)
+      }
+
+      if (typeof height !== 'number' || height === 0) {
+        throw new Error(`Failed to construct 'ImageData': The source width is zero or not a number.`)
+      }
+
+      height = height >>> 0
+
+      if ((height * 4) > width.length) {
+        throw new Error(`Failed to construct 'ImageData': The requested image size exceeds the supported range.`)
+      }
+
+      if ((width.length % 4) !== 0) {
+        throw new Error(`Failed to construct 'ImageData': The input data length is not a multiple of 4.`)
+      }
+
+      if ((width.length % (4 * height)) !== 0) {
+        throw new Error(`Failed to construct 'ImageData': The input data length is not a multiple of (4 * width).`)
+      }
+
+      if (typeof args[0] !== 'undefined') {
+        if (typeof args[0] !== 'number' || args[0] === 0) {
+          throw new Error(`Failed to construct 'ImageData': The source height is zero or not a number.`)
+        }
+
+        args[0] = args[0] >>> 0
+
+        if ((width.length % (4 * height * args[0])) !== 0) {
+          throw new Error(`Failed to construct 'ImageData': The input data length is not equal to (4 * width * height).`)
+        }
+      }
+
+      widthMap.set(this, height)
+      heightMap.set(this, typeof args[0] !== 'undefined' ? args[0] : (width.byteLength / height / 4))
+      Object.defineProperty(this, 'data', { configurable: true, enumerable: true, value: width, writable: false })
+    } else {
+      if (typeof width !== 'number' || width === 0) {
+        throw new Error(`Failed to construct 'ImageData': The source width is zero or not a number.`)
+      }
+
+      width = width >>> 0
+
+      if (typeof height !== 'number' || height === 0) {
+        throw new Error(`Failed to construct 'ImageData': The source height is zero or not a number.`)
+      }
+
+      height = height >>> 0
+
+      if ((width * height) >= (1 << 30)) {
+        throw new Error(`Failed to construct 'ImageData': The requested image size exceeds the supported range.`)
+      }
+
+      widthMap.set(this, width)
+      heightMap.set(this, height)
+      Object.defineProperty(this, 'data', { configurable: true, enumerable: true, value: new Uint8ClampedArray(width * height * 4), writable: false })
+    }
+  }
+}
+
+Object.defineProperty(ImageData.prototype, 'width', {
+  enumerable: true,
+  configurable: true,
+  get () { return widthMap.get(this) }
+})
+
+Object.defineProperty(ImageData.prototype, 'height', {
+  enumerable: true,
+  configurable: true,
+  get () { return heightMap.get(this) }
+})
+
+module.exports = ImageData