update app.py

app.py

@@ -14,12 +14,44 @@ div.stButton > button:first-child {
     unsafe_allow_html=True,
 )
 
-# Load JSON data from file
+import streamlit as st
+import json
+import ee
+import geemap
+
+# Initialize the Earth Engine library
+ee.Initialize()
+
+# Load JSON data for Sentinel dataset options
 with open("sentinel_datasets.json") as f:
     data = json.load(f)
 
-# Display title
-st.title("Sentinel Dataset Selector")
+# Define index calculation functions
+def calculate_ndvi(image):
+    """Calculate NDVI."""
+    return image.normalizedDifference(['B5', 'B4']).rename('NDVI')
+
+def calculate_ndwi(image):
+    """Calculate NDWI."""
+    return image.normalizedDifference(['B3', 'B5']).rename('NDWI')
+
+def calculate_avg_no2(image):
+    """Calculate average NO2."""
+    return image.select('NO2').reduceRegion(
+        reducer=ee.Reducer.mean(),
+        geometry=image.geometry(),
+        scale=1000
+    ).get('NO2')
+
+def calculate_custom_formula(image, formula):
+    """Apply a custom formula to the image."""
+    return image.expression(formula).rename('Custom Index')
+
+# Streamlit UI - Title
+st.title("Sentinel Dataset Selector and Earth Engine Index Calculator")
+
+# Sentinel Dataset Selector Section
+st.header("Sentinel Dataset Selector")
 
 # Step 1: Select main dataset category
 main_selection = st.selectbox("Select Sentinel Dataset Category", list(data.keys()))
@@ -34,10 +66,8 @@ if main_selection:
         bands = sub_options[sub_selection]
         st.write("Select up to 3 bands:")
 
-        # Create a list to store selected bands
-        selected_bands = []
-
         # Display bands in a side-by-side layout with three columns
+        selected_bands = []
         cols = st.columns(3)
         for i, band in enumerate(bands):
             with cols[i % 3]:
@@ -47,9 +77,50 @@ if main_selection:
                 if len(selected_bands) == 3:
                     break
 
-        # Show a warning if more than 3 bands are selected
-        if len(selected_bands) > 3:
-            st.warning("You can select a maximum of 3 bands.")
-
-        # Display selected bands
+        # Show selected bands
         st.write("Selected Bands:", selected_bands)
+
+# Earth Engine Index Calculator Section
+st.header("Earth Engine Index Calculator")
+
+# Step 1: Select Dataset for Index Calculation
+dataset_options = {
+    "Sentinel-2": "COPERNICUS/S2",
+    "Landsat 8": "LANDSAT/LC08/C01/T1_SR",
+    "NO2 Concentration": "COPERNICUS/S5P/OFFL/L3_NO2"
+}
+dataset_choice = st.selectbox("Select a Dataset for Index Calculation", list(dataset_options.keys()))
+dataset_id = dataset_options[dataset_choice]
+
+# Load dataset as an EE ImageCollection
+collection = ee.ImageCollection(dataset_id).filterDate('2020-01-01', '2020-12-31')
+
+# Step 2: Select Index or Custom Formula
+index_choice = st.selectbox("Select an Index or Enter Custom Formula", ['NDVI', 'NDWI', 'Average NO₂', 'Custom Formula'])
+
+# Step 3: Custom Formula Input
+custom_formula = ""
+if index_choice == 'Custom Formula':
+    custom_formula = st.text_input("Enter Custom Formula (e.g., 'B5 - B4 / B5 + B4')")
+
+# Step 4: Calculate and Display Results
+result_image = None
+if st.button("Calculate Index"):
+    image = collection.first()  # Using the first image in the collection as an example
+
+    if index_choice == 'NDVI':
+        result_image = calculate_ndvi(image)
+    elif index_choice == 'NDWI':
+        result_image = calculate_ndwi(image)
+    elif index_choice == 'Average NO₂':
+        result = calculate_avg_no2(image)
+        st.write("Average NO₂ Concentration:", result.getInfo())
+    elif index_choice == 'Custom Formula' and custom_formula:
+        result_image = calculate_custom_formula(image, custom_formula)
+
+    # If an index image is generated, add it to the map
+    if result_image:
+        Map = geemap.Map()
+        Map.centerObject(image, 10)
+        Map.addLayer(result_image, {}, index_choice)
+        Map.to_streamlit(height=600)