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Martin Baeuml
118 lines
3.2 KiB
ReStructuredText
118 lines
3.2 KiB
ReStructuredText
.. highlight:: python
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Concepts
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========
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Labels
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------
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The label tool is designed for labeling a set of image files or videos. Each image, or video frame,
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can contain any number of labels. The labels itself are expected to be sets key-value pairs. We can
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therefore represent a label for example in the following way::
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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 rect).
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We 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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The label tool provides support for a range of standard shape label (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 the keys are for `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 most cases, it will not be sufficient for your labeling need 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 a textual representation.
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The storage on disk of the labels however can be very different.
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The label tool does not have *the one* in which way to store the labels. Again,
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there are some default formats with which the label tool can deal out of the
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box (among others yaml and json, which resemble the textual representation
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above). However, you are free to define your own loading and saving routines
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for your labels (see :doc:`Containers`). This allows you for example to support
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legacy third-party label formats without the need of converting them to yaml
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first.
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