7. colors
— Playing with colors.¶
This module defines some colors and color conversion functions. It also defines a default palette of colors.
The following table shows the built-in colors, with their name, RGB values in 0..1 range and luminance.
>>> for k,v in PF_colors.items():
... print(f"{k:15s} = {v} -> {luminance(v):.3f}")
red = (1.0, 0.0, 0.0) -> 0.213
green = (0.0, 1.0, 0.0) -> 0.715
blue = (0.0, 0.0, 1.0) -> 0.072
cyan = (0.0, 1.0, 1.0) -> 0.787
magenta = (1.0, 0.0, 1.0) -> 0.285
yellow = (1.0, 1.0, 0.0) -> 0.928
darkred = (0.5, 0.0, 0.0) -> 0.046
darkgreen = (0.0, 0.5, 0.0) -> 0.153
darkblue = (0.0, 0.0, 0.5) -> 0.015
darkcyan = (0.0, 0.5, 0.5) -> 0.169
darkmagenta = (0.5, 0.0, 0.5) -> 0.061
darkyellow = (0.5, 0.5, 0.0) -> 0.199
pyformex_pink = (1.0, 0.2, 0.4) -> 0.246
black = (0.0, 0.0, 0.0) -> 0.000
darkgrey = (0.4, 0.4, 0.4) -> 0.133
mediumgrey = (0.6, 0.6, 0.6) -> 0.319
lightgrey = (0.8, 0.8, 0.8) -> 0.604
lightlightgrey = (0.9, 0.9, 0.9) -> 0.787
white = (1.0, 1.0, 1.0) -> 1.000
7.1. Functions defined in module colors¶
- colors.GLcolor(color)[source]¶
Convert a color to an OpenGL RGB color.
- Parameters:
color (color_like) –
Data specifying an RGB color. This can be any of the following:
a single int: returns the palette color with that index (modulo the palette length
a float: returns the grey color with that value
a string with the name of one of the built-in PF_colors
a string specifying the X11 name of the color
a hex string ‘#RGB’ with 1 to 4 hexadecimal digits per color
a tuple or list of 3 integer values in the range 0..255
a tuple or list of 3 float values in the range 0.0..1.0
a QColor or any data that can be used to create a QColor
- Returns:
tuple | ndarray – A tuple of three RGB float values, normally in the range 0.0..1.0.
Warning
There is currently no check that the result is in the range 0.0..1.0, because OpenGL allows to make clever use of values exceeding these limits. The values will be clipped at render time.
- Raises:
ValueError – If the input is not one of the accepted data.:
Examples
>>> GLcolor(2) (0.0, 1.0, 0.0) >>> GLcolor('red') (1.0, 0.0, 0.0) >>> GLcolor('indianred') (0.8039..., 0.3607..., 0.3607...) >>> GLcolor('grey90') (0.8980..., 0.8980..., 0.8980...) >>> print(GLcolor('#ff0000')) (1.0, 0.0, 0.0) >>> GLcolor("zorro") (0.0, 0.0, 0.0) >>> GLcolor(red) (1.0, 0.0, 0.0) >>> GLcolor([200,200,255]) (0.7843..., 0.7843..., 1.0) >>> GLcolor(np.array([200,200,255], dtype=np.uint8)) (0.7843..., 0.7843..., 1.0) >>> GLcolor([1.,1.,1.]) (1.0, 1.0, 1.0) >>> GLcolor(0.6) (0.6, 0.6, 0.6) >>> at.mapArray(GLcolor, ['red']) array([[1., 0., 0.]]) >>> at.mapArray(GLcolor, ['red', 'green']) array([[1., 0., 0.], [0., 1., 0.]]) >>> at.mapArray(GLcolor, [['red', 'green'], ['cyan','magenta']]) array([[[1., 0., 0.], [0., 1., 0.]], [[0., 1., 1.], [1., 0., 1.]]])
- colors.GLcolor4(color, alpha=0.5)[source]¶
Like GLcolor with alpha.
Returns tuple of shape (4,) If color does not contain alpha, adds 0.5
- colors.RGBcolor(color)[source]¶
Return an RGB (0-255) tuple for a color
color can be anything that is accepted by GLcolor.
Returns the corresponding RGB colors as a numpy array of type uint8 and shape (..,3).
Example
>>> RGBcolor(red) array([255, 0, 0], dtype=uint8)
- colors.RGBAcolor(color, alpha=0.5)[source]¶
Return an RGBA (0-255) tuple for a color and alpha value.
color can be anything that is accepted by GLcolor.
Returns the corresponding RGBA colors as a numpy array of type uint8 and shape (…, 4).
Examples
>>> RGBAcolor(yellow) array([255, 255, 0, 128], dtype=uint8) >>> RGBAcolor('yellow') array([255, 255, 0, 128], dtype=uint8) >>> RGBAcolor((1., 1., 0.)) array([255, 255, 0, 128], dtype=uint8) >>> RGBAcolor((1., 1., 0., 0.5)) array([255, 255, 0, 128], dtype=uint8) >>> RGBAcolor((255, 255, 0)) array([255, 255, 0, 128], dtype=uint8) >>> RGBAcolor((255, 255, 0, 128)) array([255, 255, 0, 128], dtype=uint8) >>> RGBAcolor(yellow, 1.0) array([255, 255, 0, 255], dtype=uint8) >>> RGBAcolor((255, 255, 255, 255)) array([255, 255, 255, 255], dtype=uint8)
- colors.WEBcolor(color)[source]¶
Return an RGB hex string for a color
color can be anything that is accepted by GLcolor. Returns the corresponding WEB color, which is a hexadecimal string representation of the RGB components.
Example
>>> WEBcolor(red) '#ff0000'
- colors.colorName(color)[source]¶
Return a string designation for the color.
color can be anything that is accepted by GLcolor. In the current implementation, the returned color name is the WEBcolor (hexadecimal string).
Example
>>> colorName('red') '#ff0000' >>> colorName('#ffddff') '#ffddff' >>> colorName([1.,0.,0.5]) '#ff0080'
- colors.luminance(color, gamma=True)[source]¶
Compute the luminance of a color.
Returns a floating point value in the range 0..1 representing the luminance of the color. The higher the value, the brighter the color appears to the human eye.
This can for example be used to derive a good contrasting foreground color to display text on a colored background. Values lower than 0.5 contrast well with white, larger value contrast better with black.
Examples
>>> print([f"{luminance(c):0.2f}" for c in ['black','red','green','blue']]) ['0.00', '0.21', '0.72', '0.07'] >>> print(luminance(np.array([black,red,green,blue]))) [0. 0.2126 0.7152 0.0722]