feat: Add preScale parameters to the image (#413)

Author: sedghi

src/imageLoader/createImage.js

@@ -196,18 +196,19 @@ function createImage(imageId, pixelData, transferSyntax, options = {}) {
         columnPixelSpacing: imagePlaneModule.columnPixelSpacing,
         columns: imageFrame.columns,
         height: imageFrame.rows,
+        preScale: imageFrame.preScale,
         intercept: modalityLutModule.rescaleIntercept
           ? modalityLutModule.rescaleIntercept
           : 0,
+        slope: modalityLutModule.rescaleSlope
+          ? modalityLutModule.rescaleSlope
+          : 1,
         invert: imageFrame.photometricInterpretation === 'MONOCHROME1',
         minPixelValue: imageFrame.smallestPixelValue,
         maxPixelValue: imageFrame.largestPixelValue,
         rowPixelSpacing: imagePlaneModule.rowPixelSpacing,
         rows: imageFrame.rows,
         sizeInBytes: imageFrame.pixelData.byteLength,
-        slope: modalityLutModule.rescaleSlope
-          ? modalityLutModule.rescaleSlope
-          : 1,
         width: imageFrame.columns,
         windowCenter: voiLutModule.windowCenter
           ? voiLutModule.windowCenter[0]

src/shared/decodeImageFrame.js

@@ -227,7 +227,12 @@ function postProcessDecodedPixels(imageFrame, options, start) {
       typeof rescaleSlope === 'number' &&
       typeof rescaleIntercept === 'number'
     ) {
-      scaleArray(pixelDataArray, scalingParameters);
+      if (scaleArray(pixelDataArray, scalingParameters)) {
+        imageFrame.preScale = {
+          scaled: true,
+          scalingParameters,
+        };
+      }
     }
   }
 

src/shared/scaling/scaleArray.js

@@ -15,4 +15,6 @@ export default function scaleArray(array, scalingParameters) {
       array[i] = array[i] * rescaleSlope + rescaleIntercept;
     }
   }
+
+  return true;
 }