Fix zoom tool aspect ratio

packages/tools/src/tools/ZoomTool.ts

@@ -193,24 +193,50 @@ class ZoomTool extends BaseTool {
     // Added spacing preset in case there is no imageData on viewport
     const imageData = viewport.getImageData();
     let spacing = [1, 1, 1];
+    let cappedParallelScale = parallelScaleToSet;
+    let thresholdExceeded = false;
+
     if (imageData) {
       spacing = imageData.spacing;
-    }
 
-    const { minZoomScale, maxZoomScale } = this.configuration;
+      const { dimensions } = imageData;
+      const imageWidth = dimensions[0] * spacing[0];
+      const imageHeight = dimensions[1] * spacing[1];
 
-    const t = element.clientHeight * spacing[1] * 0.5;
-    const scale = t / parallelScaleToSet;
+      const canvasAspect = size[0] / size[1];
 
-    let cappedParallelScale = parallelScaleToSet;
-    let thresholdExceeded = false;
+      // Get display area, if available
+      const displayArea = viewport.options?.displayArea;
+      const imageAreaScaleX = displayArea?.imageArea?.[0] ?? 1.1;
+      const imageAreaScaleY = displayArea?.imageArea?.[1] ?? 1.1;
 
-    if (imageData) {
-      if (scale < minZoomScale) {
-        cappedParallelScale = t / minZoomScale;
+      // Adjust image dimensions by display area scale
+      const scaledImageWidth = imageWidth * imageAreaScaleX;
+      const scaledImageHeight = imageHeight * imageAreaScaleY;
+      const scaledImageAspect = scaledImageWidth / scaledImageHeight;
+
+      // Determine the minimum parallel scale required to fully fit the image
+      let minParallelScaleRequired;
+      if (scaledImageAspect > canvasAspect) {
+        // Wider image, limit by width
+        minParallelScaleRequired = (scaledImageWidth / canvasAspect) * 0.5;
+      } else {
+        // Taller image, limit by height
+        minParallelScaleRequired = scaledImageHeight * 0.5;
+      }
+
+      const { minZoomScale, maxZoomScale } = this.configuration;
+
+      // Translate zoom scale limits to world-space scale
+      const minScaleInWorld = minParallelScaleRequired / maxZoomScale;
+      const maxScaleInWorld = minParallelScaleRequired / minZoomScale;
+
+      // Clamp zoom within allowed limits
+      if (parallelScaleToSet < minScaleInWorld) {
+        cappedParallelScale = minScaleInWorld;
         thresholdExceeded = true;
-      } else if (scale >= maxZoomScale) {
-        cappedParallelScale = t / maxZoomScale;
+      } else if (parallelScaleToSet > maxScaleInWorld) {
+        cappedParallelScale = maxScaleInWorld;
         thresholdExceeded = true;
       }
     }