app.py

import streamlit as st
import ee
import geemap
import datetime

# Authenticate Earth Engine
service_account = 'earth-engine-service-account@ee-esmaeilkiani1387.iam.gserviceaccount.com'
credentials = ee.ServiceAccountCredentials(service_account, 'ee-esmaeilkiani1387-1b2c5e812a1d.json')
ee.Initialize(credentials)

# Define the indices and their corresponding functions
INDICES = {
    'NDVI': lambda img: img.normalizedDifference(['B8', 'B4']).rename('NDVI'),
    'EVI': lambda img: img.expression(
        '2.5 * ((NIR - RED) / (NIR + 6 * RED - 7.5 * BLUE + 1))',
        {
            'NIR': img.select('B8'),
            'RED': img.select('B4'),
            'BLUE': img.select('B2')
        }
    ).rename('EVI'),
    'SAVI': lambda img: img.expression(
        '((NIR - RED) / (NIR + RED + 0.5)) * (1.5)',
        {
            'NIR': img.select('B8'),
            'RED': img.select('B4')
        }
    ).rename('SAVI'),
    'NDMI': lambda img: img.normalizedDifference(['B8', 'B11']).rename('NDMI')
}

# Define color palettes for each index
COLOR_PALETTES = {
    'NDVI': ['FFFFFF', 'CE7E45', 'DF923D', 'F1B555', 'FCD163', '99B718', '74A901', '66A000', '529400', '3E8601', '207401', '056201', '004C00', '023B01', '012E01', '011D01', '011301'],
    'EVI': ['FFFFFF', 'CE7E45', 'DF923D', 'F1B555', 'FCD163', '99B718', '74A901', '66A000', '529400', '3E8601', '207401', '056201', '004C00', '023B01', '012E01', '011D01', '011301'],
    'SAVI': ['#D73027', '#F46D43', '#FDAE61', '#FEE08B', '#FFFFBF', '#D9EF8B', '#A6D96A', '#66BD63', '#1A9850'],
    'NDMI': ['#D73027', '#F46D43', '#FDAE61', '#FEE08B', '#FFFFBF', '#D9EF8B', '#A6D96A', '#66BD63', '#1A9850']
}

# Streamlit app
st.title('Google Earth Engine Indices Viewer')

# User inputs
selected_indices = st.multiselect('Select two indices', list(INDICES.keys()), max_selections=2)
start_date = st.date_input('Start date', datetime.date(2022, 1, 1))
end_date = st.date_input('End date', datetime.date(2022, 12, 31))

if len(selected_indices) == 2 and start_date < end_date:
    # Define the area of interest
    aoi = ee.Geometry.Point([48.7312815, 31.5200749]).buffer(5000)

    # Get Sentinel-2 imagery
    s2 = ee.ImageCollection('COPERNICUS/S2_SR') \
        .filterBounds(aoi) \
        .filterDate(start_date, end_date) \
        .filter(ee.Filter.lt('CLOUDY_PIXEL_PERCENTAGE', 20)) \
        .sort('CLOUDY_PIXEL_PERCENTAGE')

    # Calculate indices
    for index in selected_indices:
        s2 = s2.map(lambda img: img.addBands(INDICES[index](img)))

    # Reduce the collection to a single image (median)
    image = s2.select(selected_indices).median()

    # Create a map
    m = geemap.Map()
    m.centerObject(aoi, 12)

    # Add layers to the map
    for index in selected_indices:
        m.addLayer(image.select(index), {'min': 0, 'max': 1, 'palette': COLOR_PALETTES[index]}, index)

    # Add the map to the Streamlit app
    m.to_streamlit(height=600)

else:
    st.warning('Please select two indices and ensure the start date is before the end date.')