From f2ce5ee129f44b71997680d89f78dd9cf3387fa2 Mon Sep 17 00:00:00 2001
From: Demetrio Girardi <dgirardi@prebid.org>
Date: Mon, 22 May 2023 10:45:45 -0700
Subject: [PATCH] Core: fix  in ortb -> legacy native asset conversion (#9923)

---
 src/native.js            | 24 ++++++++++++++++++++----
 test/spec/native_spec.js | 24 ++++++++++++------------
 2 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/src/native.js b/src/native.js
index 79a972371da..927423c8d72 100644
--- a/src/native.js
+++ b/src/native.js
@@ -556,6 +556,21 @@ export function toOrtbNativeRequest(legacyNativeAssets) {
   return ortb;
 }
 
+/**
+ * Greatest common divisor between two positive integers
+ * https://en.wikipedia.org/wiki/Euclidean_algorithm
+ */
+function gcd(a, b) {
+  while (a && b && a !== b) {
+    if (a > b) {
+      a = a - b;
+    } else {
+      b = b - a;
+    }
+  }
+  return a || b;
+}
+
 /**
  * This function converts an OpenRTB native request object to Prebid proprietary
  * format. The purpose of this function is to help adapters to handle the
@@ -584,12 +599,13 @@ export function fromOrtbNativeRequest(openRTBRequest) {
       if (asset.img.w && asset.img.h) {
         image.sizes = [asset.img.w, asset.img.h];
       } else if (asset.img.wmin && asset.img.hmin) {
-        image.aspect_ratios = {
+        const scale = gcd(asset.img.wmin, asset.img.hmin)
+        image.aspect_ratios = [{
           min_width: asset.img.wmin,
           min_height: asset.img.hmin,
-          ratio_width: asset.img.wmin,
-          ratio_height: asset.img.hmin
-        }
+          ratio_width: asset.img.wmin / scale,
+          ratio_height: asset.img.hmin / scale
+        }]
       }
 
       if (asset.img.type === NATIVE_IMAGE_TYPES.MAIN) {
diff --git a/test/spec/native_spec.js b/test/spec/native_spec.js
index 9150329ff60..dee177d4b9b 100644
--- a/test/spec/native_spec.js
+++ b/test/spec/native_spec.js
@@ -1002,22 +1002,22 @@ describe('validate native', function () {
 
     expect(oldNativeRequest.image).to.deep.include({
       required: false,
-      aspect_ratios: {
+      aspect_ratios: [{
         min_width: 836,
         min_height: 627,
-        ratio_width: 836,
-        ratio_height: 627
-      }
+        ratio_width: 4,
+        ratio_height: 3
+      }]
     });
 
     expect(oldNativeRequest.icon).to.deep.include({
       required: true,
-      aspect_ratios: {
+      aspect_ratios: [{
         min_width: 50,
         min_height: 50,
-        ratio_width: 50,
-        ratio_height: 50
-      }
+        ratio_width: 1,
+        ratio_height: 1
+      }]
     });
     expect(oldNativeRequest.sponsoredBy).to.include({
       required: true,
@@ -1119,12 +1119,12 @@ describe('validate native', function () {
         },
         icon: {
           required: true,
-          aspect_ratios: {
+          aspect_ratios: [{
             min_width: 50,
             min_height: 50,
-            ratio_width: 50,
-            ratio_height: 50
-          }
+            ratio_width: 1,
+            ratio_height: 1
+          }]
         },
         sponsoredBy: {
           required: true,