//选择数据集
var geometry = ee.FeatureCollection('users/lijingyu990820/wudinghe')
Map.centerObject(geometry,14);
var sentinel2 = ee.ImageCollection('COPERNICUS/S2_SR')//2A
//'COPERNICUS/S2'为1C
                  .filterDate('2020-03-01', '2020-12-31')
                  // 预先过滤以获得较少的云量。小于10%
                  .filter(ee.Filter.lt('CLOUDY_PIXEL_PERCENTAGE',10))
                  .filterBounds(geometry);
var imageMedian = sentinel2.median().clip(geometry);

// 定义重采样函数
var resampleTo10m = function(image) {
  // 重采样到 10 米分辨率，使用双线性插值
  var resampledImage = image.resample('bilinear').reproject({
    crs: 'EPSG:4326', //指定目标投影
    scale: 10
  });
  return resampledImage;
};

// 使用重采样函数对单个图像进行重采样
var resampledImage = resampleTo10m(imageMedian);


// 合并所有波段
// 选择要导出的波段
var bandB2 = resampledImage.select('B2');
var bandB3 = resampledImage.select('B3');
var bandB4 = resampledImage.select('B4');
var bandB5 = resampledImage.select('B5');
var bandB6 = resampledImage.select('B6');
var bandB7 = resampledImage.select('B7');
var bandB8 = resampledImage.select('B8');
var bandB9 = resampledImage.select('B9');
var bandB11 = resampledImage.select('B11');
// 将所选波段合并为一个多波段图像
var mergedImage = bandB2.addBands([bandB3, bandB4,bandB5, bandB6,bandB7, bandB8,bandB9, bandB11]);
//可视化 
Map.addLayer(mergedImage, {bands: ['B4', 'B3', 'B2'], min: 0,max: 3000,gamma: 1.4,}, "432");
Map.addLayer(geometry);
//Map.addLayer(dataset.median().clip(geometry), visualization, 'RGB');


// 导出图像
Export.image.toDrive({
  image: mergedImage,
  description: 'sentinel2_merged',
  crs: 'EPSG:4326',
  scale: 10,
  region: geometry,
  maxPixels: 1e13,
  folder: 'sentinel-2'
});