将[0,1]浮点值转换为十六进制颜色

Question

Is there a convenient way to convert a floating-point value in the range [0,1] to a HTML hex color using a specified gradient?

At the moment, I am using:

.myclass {fill:red, fill-opacity:FLOATINGVAL}

But this is a somewhat restrictive gradient to work with.

Answer 1

Consider something like:

def blend(color, alpha, base=[255,255,255]):
    '''
    color should be a 3-element iterable,  elements in [0,255]
    alpha should be a float in [0,1]
    base should be a 3-element iterable, elements in [0,255] (defaults to white)
    '''
    out = [int(round((alpha * color[i]) + ((1 - alpha) * base[i]))) for i in range(3)]

    return out

print blend([255,0,0], 0)       # [255, 255, 255]   (White)
print blend([255,0,0], 0.25)    # [255, 191, 191]
print blend([255,0,0], 0.5)     # [255, 128, 128]
print blend([255,0,0], 0.75)    # [255, 64, 64]
print blend([255,0,0], 1)       # [255,0,0]         (Red)

# Or RGB hex values instead of lists:
def to_hex(color):
    return ''.join(["%02x" % e for e in color])

print to_hex(blend([255,0,0], 0))       # ffffff    (White)
print to_hex(blend([255,0,0], 0.25))    # ffbfbf
print to_hex(blend([255,0,0], 0.5))     # ff8080
print to_hex(blend([255,0,0], 0.75))    # ff4040
print to_hex(blend([255,0,0], 1))       # ff0000    (Red)

In terms of how this function works with the gradients you listed [1], color is the color at the right of the gradient bars while alpha is your position on the gradient bar (0.0 far left, 1.0 far right)

[1] This will only work with 2-color gradients -- your "color" and "white" (or whatever you specify base as) (ie gradients from that image like Blues , Greens , Grays , etc.)

You won't be able to generate gradients like YlGnBu with this function.