Source code for gammapy.visualization.cmap

# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""Helper functions and functions for plotting gamma-ray images."""
from matplotlib.colors import LinearSegmentedColormap

__all__ = ["colormap_hess", "colormap_milagro"]


[docs]def colormap_hess(transition=0.5, width=0.1): """Colormap often used in H.E.S.S. collaboration publications. This colormap goes black -> blue -> red -> yellow -> white. A sharp blue -> red -> yellow transition is often used for significance images with a value of red at ``transition ~ 5`` or ``transition ~ 7`` so that the following effect is achieved: - black, blue: non-significant features, not well visible - red: features at the detection threshold ``transition`` - yellow, white: significant features, very well visible The transition parameter is defined between 0 and 1. To calculate the value from data units an `~astropy.visualization.mpl_normalize.ImageNormalize` instance should be used (see example below). Parameters ---------- transition : float (default = 0.5) Value of the transition to red (between 0 and 1). width : float (default = 0.5) Width of the blue-red color transition (between 0 and 1). Returns ------- colormap : `matplotlib.colors.LinearSegmentedColormap` Colormap Examples -------- >>> from gammapy.visualization import colormap_hess >>> from astropy.visualization.mpl_normalize import ImageNormalize >>> from astropy.visualization import LinearStretch >>> normalize = ImageNormalize(vmin=-5, vmax=15, stretch=LinearStretch()) >>> transition = normalize(5) >>> cmap = colormap_hess(transition=transition) """ # Compute normalised values (range 0 to 1) that # correspond to red, blue, yellow. red = float(transition) if width > red: blue = 0.1 * red else: blue = red - width yellow = 2.0 / 3.0 * (1 - red) + red black, white = 0, 1 # Create custom colormap # List entries: (value, (R, G, B)) colors = [ (black, "k"), (blue, (0, 0, 0.8)), (red, "r"), (yellow, (1.0, 1.0, 0)), (white, "w"), ] return LinearSegmentedColormap.from_list(name="hess", colors=colors)
[docs]def colormap_milagro(transition=0.5, width=0.0001, huestart=0.6): """Colormap often used in Milagro collaboration publications. This colormap is gray below ``transition`` and similar to the jet colormap above. A sharp gray -> color transition is often used for significance images with a transition value of ``transition ~ 5`` or ``transition ~ 7``, so that the following effect is achieved: - gray: non-significant features are not well visible - color: significant features at the detection threshold ``transition`` Note that this colormap is often criticised for over-exaggerating small differences in significance below and above the gray - color transition threshold. The transition parameter is defined between 0 and 1. To calculate the value from data units an `~astropy.visualization.mpl_normalize.ImageNormalize` instance should be used (see example below). Parameters ---------- transition : float (default = 0.5) Transition value (below: gray, above: color). width : float (default = 0.0001) Width of the transition huestart : float (default = 0.6) Hue of the color at ``transition`` Returns ------- colormap : `~matplotlib.colors.LinearSegmentedColormap` Colormap Examples -------- >>> from gammapy.visualization import colormap_milagro >>> from astropy.visualization.mpl_normalize import ImageNormalize >>> from astropy.visualization import LinearStretch >>> normalize = ImageNormalize(vmin=-5, vmax=15, stretch=LinearStretch()) >>> transition = normalize(5) >>> cmap = colormap_milagro(transition=transition) """ from colorsys import hls_to_rgb # Compute normalised red, blue, yellow values transition = float(transition) # Create custom colormap # List entries: (value, (H, L, S)) colors = [ (0, (1, 1, 0)), (transition - width, (1, 0, 0)), (transition, (huestart, 0.4, 0.5)), (transition + width, (huestart, 0.4, 1)), (0.99, (0, 0.6, 1)), (1, (0, 1, 1)), ] # Convert HLS values to RGB values rgb_colors = [(val, hls_to_rgb(*hls)) for (val, hls) in colors] return LinearSegmentedColormap.from_list(name="milagro", colors=rgb_colors)