From e794e2fb90313b7e4bb4f32abf73bd94041945eb Mon Sep 17 00:00:00 2001
From: Ouwen Huang <ouwen.huang@duke.edu>
Date: Tue, 21 Mar 2023 09:21:37 -0400
Subject: [PATCH] fix: negative checking 16 bit case (#518)

---
 src/imageLoader/createImage.js | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/imageLoader/createImage.js b/src/imageLoader/createImage.js
index 179baae9..1d77d705 100644
--- a/src/imageLoader/createImage.js
+++ b/src/imageLoader/createImage.js
@@ -57,14 +57,21 @@ function convertToIntPixelData(floatPixelData) {
 function setPixelDataType(imageFrame, preScale) {
   const isScaled = preScale?.scaled;
   const scalingParmeters = preScale?.scalingParameters;
-  const rescaleSlope = scalingParmeters?.rescaleSlope;
-  const rescaleIntercept = scalingParmeters?.rescaleIntercept;
-  const isNegative = rescaleSlope < 0 || rescaleIntercept < 0;
+  let isNegative = false;
+  if (isScaled && scalingParmeters) {
+    const rescaleSlope = scalingParmeters?.rescaleSlope || 1;
+    const rescaleIntercept = scalingParmeters?.rescaleIntercep || 0;
+    const suvbw = scalingParmeters?.suvbw || 1;
+    isNegative =
+      suvbw *
+        (imageFrame.smallestPixelValue * rescaleSlope + rescaleIntercept) <
+      0;
+  }
 
   if (imageFrame.bitsAllocated === 32) {
     imageFrame.pixelData = new Float32Array(imageFrame.pixelData);
   } else if (imageFrame.bitsAllocated === 16) {
-    if (imageFrame.pixelRepresentation === 0 && !(isScaled && isNegative)) {
+    if (imageFrame.pixelRepresentation === 0 && !isNegative) {
       imageFrame.pixelData = new Uint16Array(imageFrame.pixelData);
     } else {
       imageFrame.pixelData = new Int16Array(imageFrame.pixelData);