2021-05-07 06:20:21 +00:00
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Color Maps
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==========
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A color map defines a relationship between scalar data values and a range of colors. Color maps are
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commonly used to generate false color images, color scatter-plot points, and illustrate the height
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of surface plots.
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PyQtGraph's :class:`~pyqtgraph.ColorMap` can conveniently be applied to images and interactively
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adjusted by using :class:`~pyqtgraph.ColorBarItem`.
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To provide interactively user-defined color mappings, see
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:class:`~pyqtgraph.GradientEditorItem` and :class:`~pyqtgraph.GradientWidget`, which wraps it.
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:class:`~pyqtgraph.GradientEditorItem` combines the editing with a histogram and controls for
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interactively adjusting image levels.
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ColorMap can also be used a convenient source of colors from a consistent palette or to generate
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QPen and QBrush objects used to draw lines and fills that are colored according to their values
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along the horizontal or vertical axis.
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Sources for color maps
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----------------------
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Color maps can be user defined by assigning a number of *stops* over the range of 0 to 1. A color
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is given for each stop, and the in-between values are generated by interpolation.
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When map colors directly represent values, an improperly designed map can obscure detail over
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certain ranges of values, while creating false detail in others. PyQtGraph includes the
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perceptually uniform color maps provided by the
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`Colorcet project <https://colorcet.holoviz.org/>`_. Color maps can also be imported from the
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``colorcet`` library or from ``matplotlib``, if either of these is installed.
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To see all available color maps, please run the `ColorMap` demonstration available in the suite of
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:ref:`examples`.
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Examples
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--------
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False color display of a 2D data set. Display levels are controlled by
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a :class:`ColorBarItem <pyqtgraph.ColorBarItem>`:
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.. literalinclude:: images/gen_example_false_color_image.py
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:lines: 18-28
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:dedent: 8
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Using QtGui.QPen and QtGui.QBrush to color plots according to the plotted value:
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.. literalinclude:: images/gen_example_gradient_plot.py
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:lines: 16-33
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:dedent: 8
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.. image::
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images/example_false_color_image.png
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:width: 49%
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:alt: Example of a false color image
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.. image::
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images/example_gradient_plot.png
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:width: 49%
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:alt: Example of drawing and filling plots with gradients
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The use of color maps is also demonstrated in the `ImageView`, `Color Gradient Plots` and `ColorBarItem`
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:ref:`examples`.
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API Reference
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-------------
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.. autofunction:: pyqtgraph.colormap.listMaps
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.. autofunction:: pyqtgraph.colormap.get
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.. autofunction:: pyqtgraph.colormap.getFromMatplotlib
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.. autofunction:: pyqtgraph.colormap.getFromColorcet
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2021-06-09 03:41:46 +00:00
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.. autofunction:: pyqtgraph.colormap.modulatedBarData
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2021-05-07 06:20:21 +00:00
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2013-02-10 22:45:16 +00:00
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.. autoclass:: pyqtgraph.ColorMap
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:members:
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.. automethod:: pyqtgraph.ColorMap.__init__
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