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# Image feature enhancement

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<img src='https://g.gravizo.com/svg?
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digraph G {
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    shift [fontcolor=white,color=white];
    image -> filter -> "enhanced image";
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    node [shape=box, color=grey, fontcolor=grey];
    "enhanced image" -> "feature" [label=" aka", style=dashed, color=grey, fontcolor=grey, fontsize=10];
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    "feature enhancement" [shape=box, color=grey, fontcolor=grey, margin=0.05];
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    filter -> "feature enhancement" [label=" aka", style=dashed, color=grey, fontcolor=grey, fontsize=10];   
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}
'/>


## Difference of Gaussian (DoG) for spot enhancement

<img src='https://g.gravizo.com/svg?
 digraph G {
	shift [fontcolor=white,color=white];
	image -> "small blur";
	image -> "large blur";
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	"small blur" -> "noise filtered";
	"large blur" -> "local background";
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	"small blur" -> "DoG = small blur - large blur";
	"large blur" -> "DoG = small blur - large blur";
}
'/>

### Activity: Enhance spots in noisy image with uneven background

- Open image: xy_8bit__two_spots_noisy_uneven_background.tif
- Appreciate that you cannot simply threshold them
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- Copy image and blur with a Gaussian of small sigma -> Gs
- Copy image and blur with a Gaussian of bigger sigma -> Gb
	- For the official DoG: `rb = sqrt(2) * rs`
- Create `DoG = Gs - Gb`
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- Appreciate that you can simply threshold the DoG image
 
### Formative Assessment

TODO

### Learn more

- https://en.wikipedia.org/wiki/Difference_of_Gaussians