Add bankers rounding test case

src/processors.js

@@ -33,6 +33,7 @@ import {
     min,
     max,
     softmax,
+    bankers_round,
 } from './utils/maths.js';
 
 
@@ -174,14 +175,15 @@ function validate_audio_inputs(audio, feature_extractor) {
  * @private
  */
 function constraint_to_multiple_of(val, multiple, minVal = 0, maxVal = null) {
-    let x = Math.round(val / multiple) * multiple;
+    const a = val / multiple;
+    let x = bankers_round(a) * multiple;
 
     if (maxVal !== null && x > maxVal) {
-        x = Math.floor(val / multiple) * multiple;
+        x = Math.floor(a) * multiple;
     }
 
     if (x < minVal) {
-        x = Math.ceil(val / multiple) * multiple;
+        x = Math.ceil(a) * multiple;
     }
 
     return x;
@@ -513,8 +515,8 @@ export class ImageFeatureExtractor extends FeatureExtractor {
             if (this.config.keep_aspect_ratio && this.config.ensure_multiple_of) {
 
                 // determine new height and width
-                let scale_height = size.height / srcHeight;
-                let scale_width = size.width / srcWidth;
+                let scale_height = newHeight / srcHeight;
+                let scale_width = newWidth / srcWidth;
 
                 // scale as little as possible
                 if (Math.abs(1 - scale_width) < Math.abs(1 - scale_height)) {
@@ -765,9 +767,9 @@ export class SegformerFeatureExtractor extends ImageFeatureExtractor {
         return toReturn;
     }
 }
-export class DPTImageProcessor extends ImageFeatureExtractor { }
-export class BitImageProcessor extends ImageFeatureExtractor { }
 export class DPTFeatureExtractor extends ImageFeatureExtractor { }
+export class DPTImageProcessor extends DPTFeatureExtractor { } // NOTE: extends DPTFeatureExtractor
+export class BitImageProcessor extends ImageFeatureExtractor { }
 export class GLPNFeatureExtractor extends ImageFeatureExtractor { }
 export class CLIPFeatureExtractor extends ImageFeatureExtractor { }
 export class ChineseCLIPFeatureExtractor extends ImageFeatureExtractor { }

src/utils/maths.js

@@ -952,3 +952,17 @@ export function round(num, decimals) {
     const pow = Math.pow(10, decimals);
     return Math.round(num * pow) / pow;
 }
+
+/**
+ * Helper function to round a number to the nearest integer, with ties rounded to the nearest even number.
+ * Also known as "bankers' rounding". This is the default rounding mode in python. For example:
+ * 1.5 rounds to 2 and 2.5 rounds to 2.
+ * 
+ * @param {number} x The number to round
+ * @returns {number} The rounded number
+ */
+export function bankers_round(x) {
+    const r = Math.round(x);
+    const br = Math.abs(x) % 1 === 0.5 ? (r % 2 === 0 ? r : r - 1) : r;
+    return br;
+}

tests/maths.test.js

@@ -2,7 +2,7 @@
 import { compare } from './test_utils.js';
 
 import { getFile } from '../src/utils/hub.js';
-import { FFT, medianFilter } from '../src/utils/maths.js';
+import { FFT, medianFilter, bankers_round } from '../src/utils/maths.js';
 
 
 const fft = (arr, complex = false) => {
@@ -27,6 +27,19 @@ const fftTestsData = await (await getFile('./tests/data/fft_tests.json')).json()
 
 describe('Mathematical operations', () => {
 
+    describe('bankers rounding', () => {
+        it('should round up to nearest even', () => {
+            expect(bankers_round(-0.5)).toBe(0);
+            expect(bankers_round(1.5)).toBe(2);
+            expect(bankers_round(19.5)).toBe(20);
+        });
+        it('should round down to nearest even', () => {
+            expect(bankers_round(-1.5)).toBe(-2);
+            expect(bankers_round(2.5)).toBe(2);
+            expect(bankers_round(18.5)).toBe(18);
+        });
+    });
+
     describe('median filtering', () => {
 
 

tests/processors.test.js

@@ -52,6 +52,7 @@ describe('Processors', () => {
             pattern_3x3: 'https://huggingface.co/datasets/Xenova/transformers.js-docs/resolve/main/pattern_3x3.png',
             pattern_3x5: 'https://huggingface.co/datasets/Xenova/transformers.js-docs/resolve/main/pattern_3x5.png',
             checkerboard_8x8: 'https://huggingface.co/datasets/Xenova/transformers.js-docs/resolve/main/checkerboard_8x8.png',
+            checkerboard_64x32: 'https://huggingface.co/datasets/Xenova/transformers.js-docs/resolve/main/checkerboard_64x32.png',
             receipt: 'https://huggingface.co/datasets/Xenova/transformers.js-docs/resolve/main/receipt.png',
             tiger: 'https://huggingface.co/datasets/Xenova/transformers.js-docs/resolve/main/tiger.jpg',
             paper: 'https://huggingface.co/datasets/Xenova/transformers.js-docs/resolve/main/nougat_paper.png',
@@ -433,6 +434,7 @@ describe('Processors', () => {
         // DPTImageProcessor
         //  - tests ensure_multiple_of
         //  - tests keep_aspect_ratio
+        //  - tests bankers rounding
         it(MODELS.dpt_2, async () => {
             const processor = await AutoProcessor.from_pretrained(m(MODELS.dpt_2))
 
@@ -446,6 +448,18 @@ describe('Processors', () => {
                 compare(original_sizes, [[480, 640]]);
                 compare(reshaped_input_sizes, [[518, 686]]);
             }
+
+            {
+                const image = await load_image(TEST_IMAGES.checkerboard_64x32);
+                const { pixel_values, original_sizes, reshaped_input_sizes } = await processor(image);
+
+                // NOTE: without bankers rounding, this would be [1, 3, 266, 518]
+                compare(pixel_values.dims, [1, 3, 252, 518]);
+                compare(avg(pixel_values.data), 0.2267402559518814);
+
+                compare(original_sizes, [[32, 64]]);
+                compare(reshaped_input_sizes, [[252, 518]]);
+            }
         }, MAX_TEST_EXECUTION_TIME);
 
         // EfficientNetImageProcessor