fix(dicom-image-loader): use Float32Array for non-integer rescale slopes to prevent pixel data corruption

packages/core/src/utilities/windowLevel.ts

@@ -58,6 +58,12 @@ function toLowHighRange(
   lower: number;
   upper: number;
 } {
+  // LINEAR formula produces lower === upper when WW <= 1 because (WW-1)
+  // becomes 0. Fall back to LINEAR_EXACT to avoid division by zero. See #2706.
+  if (windowWidth <= 1 && voiLUTFunction === VOILUTFunctionType.LINEAR) {
+    voiLUTFunction = VOILUTFunctionType.LINEAR_EXACT;
+  }
+
   // Note: The SIGMOID function is currently treated the same as LINEAR
   // because we don't have a good way to define "bounds" for it.
   // Remove or statement when fixed

packages/dicomImageLoader/src/decodeImageFrameWorker.js

@@ -244,6 +244,20 @@ function _handlePreScaleSetup(
   const scalingParameters = options.preScale.scalingParameters;
   _validateScalingParameters(scalingParameters);
 
+  // Force Float32Array when scaling parameters are non-integer to avoid
+  // getPixelDataTypeFromMinMax selecting Uint8Array (Number.isInteger(1.0)
+  // is true in JS, so scaled min/max can appear integer even when values
+  // between them are fractional). See #2706.
+  const hasFloatRescale = Object.values(scalingParameters).some(
+    (v) => typeof v === 'number' && !Number.isInteger(v)
+  );
+
+  if (hasFloatRescale) {
+    const typedArray = new Float32Array(imageFrame.pixelData.length);
+    typedArray.set(imageFrame.pixelData, 0);
+    return typedArray;
+  }
+
   const scaledValues = _calculateScaledMinMax(
     minBeforeScale,
     maxBeforeScale,

packages/dicomImageLoader/src/imageLoader/setPixelDataType.ts

@@ -8,6 +8,12 @@ import getPixelDataTypeFromMinMax from '../shared/getPixelDataTypeFromMinMax';
  * min and max values
  */
 function setPixelDataType(imageFrame) {
+  // Skip re-typing if already Float32Array to prevent downgrading to
+  // Uint8Array via getPixelDataTypeFromMinMax. See #2706.
+  if (imageFrame.pixelData instanceof Float32Array) {
+    return;
+  }
+
   const minValue = imageFrame.smallestPixelValue;
   const maxValue = imageFrame.largestPixelValue;