fix alignMinDifference options (#394)

* docs: enhance tsDocs

* fix: force alignMinDifference images to be gray

* docs: correct ts docs

Author: opatiny

src/align/__tests__/alignMinDifference.test.ts

@@ -1,4 +1,4 @@
-import { ImageColorModel, overlapImages } from '../..';
+import { overlapImages } from '../..';
 import { alignMinDifference } from '../alignMinDifference';
 
 test('1 pixel source', () => {
@@ -29,9 +29,9 @@ test('4 pixels source', () => {
 });
 
 test('twice same image', () => {
-  const source = testUtils.load('opencv/test.png');
+  const source = testUtils.load('opencv/test.png').grey();
 
-  const destination = testUtils.load('opencv/test.png');
+  const destination = testUtils.load('opencv/test.png').grey();
 
   const result = alignMinDifference(source, destination);
   expect(result).toStrictEqual({ row: 0, column: 0 });
@@ -56,9 +56,7 @@ test('source too big', () => {
 test('larger image and crop', () => {
   const side = 100;
   const origin = { row: 30, column: 30 };
-  const destination = testUtils
-    .load('ssim/ssim-original.png')
-    .convertColor(ImageColorModel.RGB);
+  const destination = testUtils.load('ssim/ssim-original.png');
   const source = destination.crop({ origin, width: side, height: side });
 
   const result = alignMinDifference(source, destination);
@@ -69,9 +67,7 @@ test('larger image and crop', () => {
 test('larger image and crop 2', () => {
   const side = 100;
   const origin = { row: 50, column: 100 };
-  const destination = testUtils
-    .load('ssim/ssim-original.png')
-    .convertColor(ImageColorModel.RGB);
+  const destination = testUtils.load('ssim/ssim-original.png');
   const source = destination.crop({ origin, width: side, height: side });
 
   const result = alignMinDifference(source, destination);
@@ -80,8 +76,8 @@ test('larger image and crop 2', () => {
 });
 
 test('id crops', () => {
-  const destination = testUtils.load('align/cropped.png');
-  const source = testUtils.load('align/croppedRef.png');
+  const destination = testUtils.load('align/cropped.png').grey();
+  const source = testUtils.load('align/croppedRef.png').grey();
 
   const result = alignMinDifference(source, destination);
 
@@ -91,8 +87,8 @@ test('id crops', () => {
 });
 
 test('other id crops', () => {
-  const destination = testUtils.load('align/cropped1.png');
-  const source = testUtils.load('align/croppedRef1.png');
+  const destination = testUtils.load('align/cropped1.png').grey();
+  const source = testUtils.load('align/croppedRef1.png').grey();
   const result = alignMinDifference(source, destination);
 
   const overlap = overlapImages(source, destination, { origin: result });

src/align/alignMinDifference.ts

@@ -1,4 +1,5 @@
-import { Image, ImageColorModel, Point } from '..';
+import { Image, Point } from '..';
+import checkProcessable from '../utils/validators/checkProcessable';
 
 export interface AlignMinDifferenceOptions {
   /**
@@ -9,9 +10,8 @@ export interface AlignMinDifferenceOptions {
 }
 
 /**
- * Aligns two images by finding the translation that minimizes the mean difference
+ * Aligns two grayscale images by finding the translation that minimizes the mean difference
  * between them. The source image should fit entirely in the destination image.
- * The images are converted to grayscale internally.
  * @param source - Image to align.
  * @param destination - Image to align to.
  * @param options - Align images min difference options.
@@ -23,6 +23,8 @@ export function alignMinDifference(
   destination: Image,
   options: AlignMinDifferenceOptions = {},
 ): Point {
+  checkProcessable(source, { components: 1, bitDepth: [8, 16], alpha: false });
+
   const xSpan = destination.width - source.width;
   const ySpan = destination.height - source.height;
   const {
@@ -38,13 +40,6 @@ export function alignMinDifference(
     throw new Error('Source image must fit entirely in destination image');
   }
 
-  if (source.colorModel !== ImageColorModel.GREY) {
-    source = source.grey();
-  }
-  if (destination.colorModel !== ImageColorModel.GREY) {
-    destination = destination.grey();
-  }
-
   let bestDifference = Number.POSITIVE_INFINITY;
   let bestShiftX = 0;
   let bestShiftY = 0;

src/featureMatching/keypoints/getHarrisScore.ts

@@ -12,7 +12,7 @@ export interface GetHarrisScoreOptions {
    */
   windowSize?: number;
   /**
-   * Constant for the score computation. Should be between 0.04 and 0.06 (empirical values).
+   * Constant for the score computation. Should be between 0.04 and 0.06 (empirical values). This consant is commonly called k.
    * @default `0.04`
    */
   harrisConstant?: number;