feat: implement enhanceContrast

Author: opatiny

src/filters/__tests__/__image_snapshots__/enhance-contrast-test-ts-bigger-image-1-snap.png

@@ -0,0 +1,53 @@
+import { enhanceContrast } from '../enhanceContrast';
+
+test('3x1 rgba image, custom output min and max', () => {
+  const image = testUtils.createRgbaImage([
+    [0, 100, 0, 50],
+    [127, 150, 0, 50],
+    [255, 200, 0, 50],
+  ]);
+
+  const result = enhanceContrast(image);
+
+  expect(result).toMatchImageData([
+    [0, 0, 0, 50],
+    [127, 127, 0, 50],
+    [255, 255, 0, 50],
+  ]);
+});
+
+test('1x3 grey image', () => {
+  const image = testUtils.createGreyImage([[50, 100]]);
+  expect(enhanceContrast(image)).toMatchImageData([[0, 255]]);
+});
+
+test('alpha should not be modified', () => {
+  const image = testUtils.createGreyaImage([
+    [50, 100],
+    [100, 50],
+  ]);
+  expect(enhanceContrast(image)).toMatchImageData([
+    [0, 100],
+    [255, 50],
+  ]);
+});
+
+test('out option', () => {
+  const image = testUtils.createGreyaImage([
+    [0, 10],
+    [30, 40],
+    [60, 70],
+  ]);
+  const result = enhanceContrast(image, { out: image });
+  expect(result).toMatchImageData([
+    [0, 10],
+    [127, 40],
+    [255, 70],
+  ]);
+  expect(result).toBe(image);
+});
+
+test('bigger image', () => {
+  const image = testUtils.load('featureMatching/id-crops/crop1.png');
+  expect(enhanceContrast(image)).toMatchImageSnapshot();
+});

src/filters/__tests__/enhanceContrast.test.ts

@@ -0,0 +1,50 @@
+import { Image } from '../Image';
+import checkProcessable from '../utils/checkProcessable';
+import { ImageColorModel } from '../utils/constants/colorModels';
+import { getOutputImage } from '../utils/getOutputImage';
+
+export interface EnhanceContrastOptions {
+  /**
+   * Image to which to output.
+   */
+  out?: Image;
+}
+
+/**
+ * Enhance the contrast of an image by spanning each channel on the range [0, image.maxValue].
+ *
+ * @param image - The image to enhance.
+ * @param options - Enhance contrast options.
+ * @returns The enhanced image.
+ */
+export function enhanceContrast(
+  image: Image,
+  options: EnhanceContrastOptions = {},
+): Image {
+  checkProcessable(image, {
+    bitDepth: [8, 16],
+  });
+
+  let newImage = getOutputImage(image, options, { clone: true });
+
+  const minMax = image.minMax();
+
+  let channels: number[] = new Array(image.components)
+    .fill(0)
+    .map((value, index) => index);
+
+  if (image.colorModel === ImageColorModel.GREYA) {
+    channels = [0];
+  } else if (image.colorModel === ImageColorModel.RGBA) {
+    channels = [0, 1, 2];
+  }
+
+  return newImage.level({
+    inputMin: minMax.min,
+    inputMax: minMax.max,
+    outputMin: 0,
+    outputMax: image.maxValue,
+    channels,
+    ...options,
+  });
+}

src/filters/enhanceContrast.ts

@@ -2,6 +2,7 @@ export * from './and';
 export * from './blur';
 export * from './convolution';
 export * from './derivativeFilter';
+export * from './enhanceContrast';
 export * from './gaussianBlur';
 export * from './gradientFilter';
 export * from './hypotenuse';