Updates an image's mask at all positions where the existing mask is not zero using the value of the image as the new mask value. The output image retains the metadata and footprint of the input image.

<br />

| Usage | Returns |
|---|---|
| `Image.selfMask()` | Image |

| Argument | Type | Details |
|---|---|---|
| this: `image` | Image | The image to mask with itself. |

## Examples

### Code Editor (JavaScript)

```javascript
// A Sentinel-2 surface reflectance image.
var img = ee.Image('COPERNICUS/S2_SR_HARMONIZED/20210109T185751_20210109T185931_T10SEG');
var trueColorViz = {
  bands: ['B4', 'B3', 'B2'],
  min: 0,
  max: 2700,
  gamma: 1.3
};
print('Sentinel-2 image', img);
Map.setCenter(-122.36, 37.47, 10);
Map.addLayer(img, trueColorViz, 'Sentinel-2 image');

// Create a Boolean land mask from the SWIR1 band; water is value 0, land is 1.
var landMask = img.select('B11').gt(100);
print('Land mask', landMask);
Map.addLayer(landMask, {palette: ['blue', 'lightgreen']}, 'Land mask');

// Mask the land mask by itself; pixel values equal to 0 (water) become invalid.
var landMaskMasked = landMask.selfMask();
print('Land mask, masked', landMaskMasked);
Map.addLayer(landMaskMasked, {palette: ['gold']}, 'Land mask, masked');
```
Python setup

See the [Python Environment](https://developers.google.com/earth-engine/guides/python_install) page for information on the Python API and using
`geemap` for interactive development.

```python
import ee
import geemap.core as geemap
```

### Colab (Python)

```python
# A Sentinel-2 surface reflectance image.
img = ee.Image('COPERNICUS/S2_SR_HARMONIZED/20210109T185751_20210109T185931_T10SEG')
true_color_viz = {
    'bands': ['B4', 'B3', 'B2'],
    'min': 0,
    'max': 2700,
    'gamma': 1.3,
}
display('Sentinel-2 image', img)
m = geemap.Map()
m.set_center(-122.36, 37.47, 10)
m.add_layer(img, true_color_viz, 'Sentinel-2 image')

# Create a Boolean land mask from the SWIR1 band water is value 0, land is 1.
land_mask = img.select('B11').gt(100)
display('Land mask', land_mask)
m.add_layer(land_mask, {'palette': ['blue', 'lightgreen']}, 'Land mask')

# Mask the land mask by itself pixel values equal to 0 (water) become invalid.
land_mask_masked = land_mask.selfMask()
display('Land mask, masked', land_mask_masked)
m.add_layer(land_mask_masked, {'palette': ['gold']}, 'Land mask, masked')
m
```