feat: add options to mean, median and variance

src/Image.ts

@@ -4,8 +4,13 @@ import { Mask } from './Mask';
 import { add, subtract, SubtractImageOptions } from './compare';
 import { divide, DivideOptions } from './compare/divide';
 import { multiply, MultiplyOptions } from './compare/multiply';
-import { median } from './compute';
-import { variance } from './compute/variance';
+import {
+  MedianOptions,
+  MeanOptions,
+  median,
+  VarianceOptions,
+  variance,
+} from './compute';
 import { correctColor } from './correctColor';
 import {
   drawCircleOnImage,
@@ -707,26 +712,29 @@ export class Image {
 
   /**
    * Compute the mean pixel of an image.
+   * @param options - Mean options.
    * @returns The mean pixel.
    */
-  public mean(): number[] {
-    return mean(this);
+  public mean(options?: MeanOptions): number[] {
+    return mean(this, options);
   }
 
   /**
    * Compute the median pixel of an image.
+   * @param options - Median options.
    * @returns The median pixel.
    */
-  public median(): number[] {
-    return median(this);
+  public median(options?: MedianOptions): number[] {
+    return median(this, options);
   }
 
   /**
    * Compute the variance of each channel of an image.
+   * @param options - Variance options.
    * @returns The variance of the channels of the image.
    */
-  public variance(): number[] {
-    return variance(this);
+  public variance(options?: VarianceOptions): number[] {
+    return variance(this, options);
   }
 
   // DRAW

src/compute/__tests__/mean.test.ts

@@ -1,3 +1,4 @@
+import { Point } from '../../geometry';
 import { mean } from '../mean';
 
 test('5x1 RGB image', () => {
@@ -38,3 +39,78 @@ test('2x4 GREY image', () => {
 
   expect(result).toStrictEqual([1.5]);
 });
+test('mean from points', () => {
+  const image = testUtils.createGreyImage([
+    [1, 2, 3, 0],
+    [1, 2, 3, 0],
+  ]);
+  const points = [
+    { column: 0, row: 0 },
+    { column: 1, row: 0 },
+    { column: 2, row: 1 },
+  ];
+  const result = image.mean({ points });
+
+  expect(result).toStrictEqual([2]);
+});
+test('mean from points in rgba image', () => {
+  const image = testUtils.createRgbaImage([
+    [1, 2, 3, 0],
+    [1, 2, 3, 0],
+  ]);
+  const points = [
+    { column: 0, row: 0 },
+    { column: 0, row: 1 },
+  ];
+  const result = image.mean({ points });
+
+  expect(result).toStrictEqual([1, 2, 3, 0]);
+});
+test('must throw if array is empty', () => {
+  const image = testUtils.createRgbaImage([
+    [1, 2, 3, 0],
+    [1, 2, 3, 0],
+  ]);
+  const points: Point[] = [];
+
+  expect(() => {
+    const result = image.mean({ points });
+    return result;
+  }).toThrow('Array of coordinates is empty.');
+});
+test("must throw if point's row is invalid.", () => {
+  const image = testUtils.createRgbaImage([
+    [1, 2, 3, 0],
+    [1, 2, 3, 0],
+  ]);
+  const points: Point[] = [{ column: 0, row: 2 }];
+
+  expect(() => {
+    const result = image.mean({ points });
+    return result;
+  }).toThrow('Invalid coordinate: {column: 0, row: 2}');
+});
+test("must throw if point's column is invalid.", () => {
+  const image = testUtils.createRgbaImage([
+    [1, 2, 3, 0],
+    [1, 2, 3, 0],
+  ]);
+  const points: Point[] = [{ column: 4, row: 1 }];
+
+  expect(() => {
+    const result = image.mean({ points });
+    return result;
+  }).toThrow('Invalid coordinate: {column: 4, row: 1}');
+});
+test('must throw if point has negative values.', () => {
+  const image = testUtils.createRgbaImage([
+    [1, 2, 3, 0],
+    [1, 2, 3, 0],
+  ]);
+  const points: Point[] = [{ column: -14, row: 0 }];
+
+  expect(() => {
+    const result = image.mean({ points });
+    return result;
+  }).toThrow('Invalid coordinate: {column: -14, row: 0}');
+});

src/compute/__tests__/median.test.ts

@@ -1,3 +1,4 @@
+import { Point } from '../../geometry';
 import { median } from '../median';
 
 test('5x1 RGB image', () => {
@@ -38,3 +39,82 @@ test('2x4 GREY image', () => {
 
   expect(result).toStrictEqual([2]);
 });
+
+test('median from points', () => {
+  const image = testUtils.createGreyImage([
+    [1, 2, 2, 2],
+    [1, 2, 3, 2],
+  ]);
+  const points = [
+    { column: 0, row: 0 },
+    { column: 2, row: 1 },
+    { column: 1, row: 0 },
+  ];
+
+  const result = image.median({ points });
+
+  expect(result).toStrictEqual([2]);
+});
+
+test('median from points on rgba image', () => {
+  const image = testUtils.createRgbaImage([
+    [1, 2, 2, 2],
+    [1, 2, 3, 2],
+  ]);
+  const points = [
+    { column: 0, row: 0 },
+    { column: 0, row: 1 },
+  ];
+
+  const result = image.median({ points });
+
+  expect(result).toStrictEqual([1, 2, 2, 2]);
+});
+
+test('must throw if array is empty', () => {
+  const image = testUtils.createRgbaImage([
+    [1, 2, 2, 2],
+    [1, 2, 3, 2],
+  ]);
+  const points: Point[] = [];
+  expect(() => {
+    const result = image.median({ points });
+    return result;
+  }).toThrow('Array of coordinates is empty.');
+});
+
+test("must throw if point's row is invalid", () => {
+  const image = testUtils.createRgbaImage([
+    [1, 2, 2, 2],
+    [1, 2, 3, 2],
+  ]);
+  const points: Point[] = [{ column: 0, row: 2 }];
+  expect(() => {
+    const result = image.median({ points });
+    return result;
+  }).toThrow('Invalid coordinate: {column: 0, row: 2}');
+});
+
+test("must throw if point's column is invalid", () => {
+  const image = testUtils.createRgbaImage([
+    [1, 2, 2, 2],
+    [1, 2, 3, 2],
+  ]);
+  const points: Point[] = [{ column: 4, row: 1 }];
+  expect(() => {
+    const result = image.median({ points });
+    return result;
+  }).toThrow('Invalid coordinate: {column: 4, row: 1}');
+});
+test('must throw if point has negative values.', () => {
+  const image = testUtils.createRgbaImage([
+    [1, 2, 3, 0],
+    [1, 2, 3, 0],
+  ]);
+  const points: Point[] = [{ column: -14, row: 0 }];
+
+  expect(() => {
+    const result = image.mean({ points });
+    return result;
+  }).toThrow('Invalid coordinate: {column: -14, row: 0}');
+});

src/compute/__tests__/variance.test.ts

@@ -1,3 +1,4 @@
+import { Point } from '../../geometry';
 import { variance } from '../variance';
 
 test('1x1 RGB image', () => {
@@ -16,3 +17,66 @@ test('GREY image', () => {
 
   expect(result).toStrictEqual([525]);
 });
+
+test('variance from points', () => {
+  const image = testUtils.createGreyImage([
+    [10, 20, 30, 40],
+    [50, 60, 70, 80],
+  ]);
+
+  const points = [
+    { column: 0, row: 0 },
+    { column: 1, row: 0 },
+    { column: 2, row: 0 },
+    { column: 3, row: 0 },
+  ];
+
+  const result = image.variance({ points });
+
+  expect(result).toStrictEqual([125]);
+});
+test('must throw if array is empty', () => {
+  const image = testUtils.createRgbaImage([
+    [1, 2, 2, 2],
+    [1, 2, 3, 2],
+  ]);
+  const points: Point[] = [];
+  expect(() => {
+    const result = image.median({ points });
+    return result;
+  }).toThrow('Array of coordinates is empty.');
+});
+test("must throw if point's coordinates are invalid", () => {
+  const image = testUtils.createGreyImage([
+    [1, 2, 2, 2],
+    [1, 2, 3, 2],
+  ]);
+  const points: Point[] = [{ column: 0, row: 2 }];
+  expect(() => {
+    const result = image.median({ points });
+    return result;
+  }).toThrow('Invalid coordinate: {column: 0, row: 2}');
+});
+test("must throw if point's coordinates are invalid", () => {
+  const image = testUtils.createGreyImage([
+    [1, 2, 2, 2],
+    [1, 2, 3, 2],
+  ]);
+  const points: Point[] = [{ column: 4, row: 1 }];
+  expect(() => {
+    const result = image.median({ points });
+    return result;
+  }).toThrow('Invalid coordinate: {column: 4, row: 1}');
+});
+test('must throw if point has negative values.', () => {
+  const image = testUtils.createRgbaImage([
+    [1, 2, 3, 0],
+    [1, 2, 3, 0],
+  ]);
+  const points: Point[] = [{ column: -14, row: 0 }];
+
+  expect(() => {
+    const result = image.mean({ points });
+    return result;
+  }).toThrow('Invalid coordinate: {column: -14, row: 0}');
+});

src/compute/index.ts

@@ -2,3 +2,4 @@ export * from './mean';
 export * from './histogram';
 export * from './median';
 export * from './getExtrema';
+export * from './variance';

src/compute/mean.ts

@@ -1,19 +1,48 @@
 import { Image } from '../Image';
+import { Point } from '../geometry';
+
+export interface MeanOptions {
+  /**
+   * Points to calculate mean from.
+   */
+  points: Point[];
+}
 
 /**
  * Compute the mean of an image. The mean can be either computed on each channel
  * individually or on the whole image.
  * @param image - Image to process.
+ * @param options - Mean options.
  * @returns The mean pixel.
  */
-export function mean(image: Image): number[] {
-  const pixel = new Array<number>(image.channels).fill(0);
-  for (let row = 0; row < image.height; row++) {
-    for (let column = 0; column < image.width; column++) {
+export function mean(image: Image, options?: MeanOptions): number[] {
+  const pixelSum = new Array<number>(image.channels).fill(0);
+  const nbValues = options ? options.points.length : image.size;
+  if (nbValues === 0) throw new RangeError('Array of coordinates is empty.');
+  if (options) {
+    for (const point of options.points) {
       for (let channel = 0; channel < image.channels; channel++) {
-        pixel[channel] += image.getValue(column, row, channel);
+        if (
+          point.column < 0 ||
+          point.column >= image.width ||
+          point.row < 0 ||
+          point.row >= image.height
+        ) {
+          throw new RangeError(
+            `Invalid coordinate: {column: ${point.column}, row: ${point.row}}.`,
+          );
+        }
+        pixelSum[channel] += image.getValueByPoint(point, channel);
+      }
+    }
+  } else {
+    for (let row = 0; row < image.height; row++) {
+      for (let column = 0; column < image.width; column++) {
+        for (let channel = 0; channel < image.channels; channel++) {
+          pixelSum[channel] += image.getValue(column, row, channel);
+        }
       }
     }
   }
-  return pixel.map((channel) => channel / image.size);
+  return pixelSum.map((channelSum) => channelSum / nbValues);
 }