docs: Updated guide/index.md to remove the part to set ROI in SimplifiedSettings, promote only setScanRegion with DCE [Reason: this guide is for starting users]

Author: Tom-Dynamsoft

programming/javascript/user-guide/index.md

@@ -543,6 +543,30 @@ await cvRouter.startCapturing("ReadSingleBarcode");
 
 ##### Specify a scan region
 
+We can specify a scan region to allow the SDK to process only part of the image, improving processing speed. The code snippet below demonstrates how to do this using the `cameraEnhancer` image source.
+```javascript
+cameraEnhancer = await Dynamsoft.DCE.CameraEnhancer.createInstance(cameraView);
+cameraEnhancer.setScanRegion({
+  x: 25,
+  y: 25,
+  width: 50,
+  height: 50,
+  isMeasuredInPercentage: true,
+});
+```
+
+*Note*:
+
+1. By configuring the region at the image source, images are cropped before processing, removing the need to adjust any further processing settings.
+2. `cameraEnhancer` enhances interactivity by overlaying a mask on the video, clearly marking the scanning region.
+
+*See Also*:
+
+[CameraEnhancer::setScanRegion](https://www.dynamsoft.com/camera-enhancer/docs/web/programming/javascript/api-reference/acquisition.html#setscanregion)
+
+<!-- Since DCE is always used, no need to use this approach
+
+
 You can use the parameter `roi` (region of interest) together with the parameter `roiMeasuredInPercentage` to configure the SDK to only read a specific region on the image frames. For example, the following code limits the reading in the center 25%( = 50% * 50%) of the image frames:
 
 ```javascript
@@ -556,24 +580,8 @@ settings.roi.points = [
 ];
 await cvRouter.updateSettings("ReadSingleBarcode", settings);
 await cvRouter.startCapturing("ReadSingleBarcode");
-```
-
-While the code above accomplishes the task, a more effective approach is to restrict the scan region directly at the image source, as demonstrated in the following code snippet.
+``` -->
 
-> * With the region configured at the image source, the images are cropped right before they are gathered for processing, eliminating the necessity to modify the processing settings further.
-> * `cameraEnhancer` elevates interactivity by overlaying a mask on the video, providing a clear delineation of the scanning region.
-> * See also: [CameraEnhancer::setScanRegion](https://www.dynamsoft.com/camera-enhancer/docs/web/programming/javascript/api-reference/acquisition.html#setscanregion)
-
-```javascript
-cameraEnhancer = await Dynamsoft.DCE.CameraEnhancer.createInstance(cameraView);
-cameraEnhancer.setScanRegion({
-  x: 25,
-  y: 25,
-  width: 50,
-  height: 50,
-  isMeasuredInPercentage: true,
-});
-```
 
 <!--
 * Specify the maximum time allowed for processing each image
@@ -730,4 +738,4 @@ Now that you have got the SDK integrated, you can choose to move forward in the
 
 1. Learn how to [Use in Framework](https://www.dynamsoft.com/barcode-reader/docs/web/programming/javascript/user-guide/use-in-framework.html)
 2. Check out the [Official Samples and Demo](https://www.dynamsoft.com/barcode-reader/docs/web/programming/javascript/samples-demos/index.html?ver=10.2.10)
-3. Learn about the [APIs of the SDK](https://www.dynamsoft.com/barcode-reader/docs/web/programming/javascript/api-reference/index.html?ver=10.2.10)
+3. Learn about the [APIs of the SDK](https://www.dynamsoft.com/barcode-reader/docs/web/programming/javascript/api-reference/index.html?ver=10.2.10)