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Add Heatmap
===========
Heatmap is an optional [ArFrame](../../argaze.md/#argaze.ArFeatures.ArFrame) pipeline step. It is executed at each new gaze position to update heatmap image.
## Enable and display ArFrame heatmap
[ArFrame.heatmap](../../argaze.md/#argaze.ArFeatures.ArFrame.heatmap) can be enabled thanks to a dedicated JSON entry.
Here is the JSON ArFrame configuration file example where heatmap is enabled and displayed:
```json
{
"name": "My FullHD screen",
"size": [1920, 1080],
...
"heatmap": {
"size": [320, 180],
"sigma": 0.025,
"buffer": 0
},
...
"image_parameters": {
...
"heatmap_weight": 1
}
}
```
Then, here is how to access to heatmap object:
```python
# Assuming an ArFrame is loaded
...
print("heatmap:", ar_frame.heatmap)
```
Finally, here is what the program writes in console:
```txt
heatmap: Heatmap(size=[320, 180], buffer=0, sigma=0.025)
```
Now, let's understand the meaning of each JSON entry.
### Size
The heatmap image size in pixel. Higher size implies higher CPU load.
### Sigma
The gaussian point spreading to draw at each gaze position.
### Buffer
The size of point spread images buffer (0 means no buffering) to visualize only last N gaze positions.
### Heatmap weight
The weight of heatmap overlay in [ArFrame.image](../../argaze.md/#argaze.ArFeatures.ArFrame.image) between 0 and 1.
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