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Martin Baeuml
2edb6f83ca
- split item and inserters api documentation - fix some links - fix warning about too short title underlines - fix code for importing default config - update front page/index
124 lines
3.2 KiB
ReStructuredText
124 lines
3.2 KiB
ReStructuredText
.. highlight:: python
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========
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Concepts
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========
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In this section, we will introduces some high-level concepts in sloth.
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Labels
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------
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Sloth is designed for labeling a set of images or videos. Each image, or video frame,
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can contain any number of labels. The labels itself are represented as key-value pairs,
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for example::
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{
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type: "rect",
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id: "Martin",
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x: 10,
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y: 30,
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width: 40,
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height: 50,
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}
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The only required key a label *has* to have is the "type" key. It will be used by the label tool
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to determine the appropriate visualization for this label (in our example it will draw a rectangle).
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You will later see, how you can customize the mapping between type and visualization and how to
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write your own visualizations.
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Label type conventions
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----------------------
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Sloth provides support for a range of standard shape labels (for example `rect`, `point`, `polygon` etc.).
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In order for the label tool to correctly visualize these labels, the labels have to follow
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a convention, which keys represent the `x`- and `y`-coordinates, `width` and `height` and so on.
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The following types are supported out of the box, i.e. corresponding visualization items
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and inserters will be avaible in the default configuration.
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Point
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.....
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::
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{
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"type": "point",
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"x": 10,
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"y": 20,
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}
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Rect
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....
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::
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{
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"type": "rect",
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"x": 10,
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"y": 20,
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"width": 20,
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"height": 20,
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}
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Polygon
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.......
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::
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{
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"type": "polygon",
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"xn": "10;20;30",
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"yn": "20;30;40",
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}
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User defined labels
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-------------------
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In many cases, it will not be sufficient for your labeling needs to stick to those simple types. Or
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your might want to add further information. Since each label is just a set of key-value pairs, this
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is easily possible. For example, by adding an additional ``class`` key, denoting that these points
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are the left and right eye, respectively::
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{
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"type": "point",
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"class": "left_eye",
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x: 50, y: 40,
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}
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{
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"type": "point",
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"class": "right_eye",
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x: 70, y: 40,
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}
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Of course, you can also change the type::
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{
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"type": "triangle",
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"x1": 10,
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"y1": 20,
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"x2": 30,
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"y2": 20,
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"x3": 20,
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"y3": 30,
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}
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However, if you do this you will need to tell the label tool in the
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configuration how to display this type as well. See section
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:doc:`configuration` on how to do that.
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Representation is not storage
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-----------------------------
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In the sections above we introduced the labels as sets of key-value pairs with
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a textual representation. The storage on disk of the labels however can be
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very different. Sloth does not have *the one* way in which way to store the
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labels. Again, there are some default formats which the label tool can deal
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with out of the box (among others YAML and JSON, which resemble the textual
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representation above). However, you are free to define your own loading and
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saving routines for your labels (see :doc:`containers`). This allows you for
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example to support legacy third-party label formats without the need of
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converting them to JSON first.
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