// Canny 邊緣檢測器示例。
// 加載圖像并從中計算 NDVI。
var image = ee.Image('LANDSAT/LT05/C01/T1_TOA/LT05_031034_20110619');
//用内置函數波段計算NDVI
var ndvi = image.normalizedDifference(['B4','B3']);
// 檢測合成中的邊緣,這裡面設定的數值為0.7
var canny = ee.Algorithms.CannyEdgeDetector(ndvi, 0.7);
// 用自身屏蔽圖像以去除沒有邊緣的區域。
canny = canny.updateMask(canny);
Map.setCenter(-101.05259, 37.93418, 13);
Map.addLayer(ndvi, {min: 0, max: 1}, 'Landsat NDVI');
Map.addLayer(canny, {min: 0, max: 1, Palette: 'FF0000'}, 'Canny Edges');
具體代碼如下(ndvi>0.7):
// Canny Edge Detector example.
// Load an image and compute NDVI from it.
var image = ee.Image('LANDSAT/LT05/C01/T1_TOA/LT05_031034_20110619');
var ndvi = image.normalizedDifference(['B4','B3']);
// Detect edges in the composite.
var canny = ee.Algorithms.CannyEdgeDetector(ndvi, 0.7);
// Mask the image with itself to get rid of areas with no edges.
canny = canny.updateMask(canny);
Map.setCenter(-101.05259, 37.93418, 13);
Map.addLayer(ndvi, {min: 0, max: 1}, 'Landsat NDVI');
Map.addLayer(canny, {min: 0, max: 1, palette: 'FF0000'}, 'Canny Edges');
最後識别結果圖:NDVI>0.7
NDVI> 0.5