Fixed the lack of mask for LEL images (#1292)

* Fixed the lack of mask for LEL images

* Add a check for the LEL image mask data

---------

Co-authored-by: Adrianna Pińska <adrianna.pinska@gmail.com>

CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Fixed the case-sensitive of reading BUNIT from a file header ([#1187](https://github.com/CARTAvis/carta-backend/issues/1187)).
 * Fixed the crash when reading beam table with 64-bit floats ([#1166](https://github.com/CARTAvis/carta-backend/issues/1166)).
 * Fixed region spectral profile from FITS gz image ([#1271](https://github.com/CARTAvis/carta-backend/issues/1271)).
+* Fixed the lack of mask for LEL images ([#1291](https://github.com/CARTAvis/carta-backend/issues/1291)).
 * Fixed file path to save generated image ([#1252](https://github.com/CARTAvis/carta-backend/issues/1252)).
 
 ## [4.0.0-beta.1]

src/ImageData/FileLoader.cc

@@ -339,6 +339,24 @@ bool FileLoader::GetSlice(casacore::Array<float>& data, const StokesSlicer& stok
             // Use ImageExpr for slice
             casacore::Array<float> slice_data;
             image->doGetSlice(slice_data, slicer);
+
+            if (image->isMasked()) {
+                // Get mask data
+                casacore::Array<bool> mask_data;
+                image->getMaskSlice(mask_data, slicer);
+
+                if (mask_data.shape() == slice_data.shape()) {
+                    // Reset the pixel value as NaN if its mask is false
+                    casacore::Array<float>::iterator slice_data_iter = slice_data.begin();
+                    casacore::Array<bool>::iterator mask_data_iter = mask_data.begin();
+                    for (; slice_data_iter != slice_data.end(); ++slice_data_iter, ++mask_data_iter) {
+                        if (!*mask_data_iter) {
+                            *slice_data_iter = NAN;
+                        }
+                    }
+                }
+            }
+
             data = slice_data; // copy from reference
             return true;
         } else if (image_type == "RebinImage") {