Earth Engine, how to convert 0 pixel values to transparent or nodata?

Question

I'm using the following snippet to convert canny edges to black and white to highlight boundaries. However, I want to fill the black area with transparent or NODATA, is there a way to do this in EE?

var final_stacked_canny = ee.Algorithms.CannyEdgeDetector({
  image: final_stacked, threshold: 0.7
}).multiply(255);

var perimeterPixelsCanny = final_stacked_canny.select(1).neq(final_stacked_canny.select(0)).rename('perimeter')
Map.addLayer(perimeterPixelsCanny, {}, "Canny On CCCI + GOSAVI + EVI", false)

Answer 1

gt() and selfMask() on the canny edge image will do the trick. Use for the gt() value the same value as you use in the threshold argument for the CannyEdgeDetector:

var canny = ee.Algorithms.CannyEdgeDetector({
  image: image.select('B5'), threshold: threshold
});

// mask everything but the edges
var cannyMasked = canny.gt(threshold) // edges will be 1, everything else 0
                      .selfMask() // to mask every pixel which eq 0

See here a simplified example