Gee (6): set the number of decimal places reserved for the calculated value / image

For numbers and images, it is sometimes necessary to preserve the results N Decimal place , Numbers and images retain decimal places in different ways , Here are their introductions .

stay GEE in ee.Number Of API, There's a way format(), It is to set the number format .
For example, the above requirements are ee.Number(10.123456789).format('%.3f’). It should be noted that what is returned here is a string , If there are other calculations to be used later ee.Number.parse() To convert .
1. Numbers ：

// Suppose the calculation result is a Is a decimal 
var a = 1.23456789;
// Want to keep three decimal places for the calculation result , At this time, the conversion result is of string type 
var b = ee.Number(a).format('%.3f');
print(b);
// It can be used ee.Number.parse() Convert it to Number type 
var c = ee.Number.parse(b);
var d = c.add(3);
print(c,d);

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2. image
If it is image calculation , Want to keep it n Calculation result of decimal places , For example, calculated NDVI, Want to keep the results 5 Decimal place , It can be expanded by a certain number of times , Then convert it to an integer , Divide by this multiple .
Example ：

// Image retention 5 Decimal place 
// For example, the calculation result of the original image is img 
var img = ee.Image.constant(1.23456789); 
Map.addLayer(img, {
    }, "img"); 
//1.23456789×100000=123456.789, Convert to integer type as ：123456
//123456÷100000=1.23456
var newImg = img.multiply(100000).toInt().divide(100000); 
Map.addLayer(newImg, {
    }, "newImg");

Here, first expand the image 100000 times , Turn it into INT type , Divided by 100000, To get the desired results .