colors - 色彩缩放功能

Question

我正在尝试在表单上可视化一些值。它们的范围从 0 到 200，我希望 0 附近的那些是绿色的，当它们达到 200 时变成鲜红色。

基本上该函数应该根据输入的值返回颜色。有什么想法吗？

Answer 1

基本上，两个值之间平滑过渡的一般方法是以下函数:

function transition(value, maximum, start_point, end_point):
    return start_point + (end_point - start_point)*value/maximum

鉴于此，您定义一个函数来执行三元组(RGB、HSV 等)的转换。

function transition3(value, maximum, (s1, s2, s3), (e1, e2, e3)):
    r1= transition(value, maximum, s1, e1)
    r2= transition(value, maximum, s2, e2)
    r3= transition(value, maximum, s3, e3)
    return (r1, r2, r3)

假设您有 s 和 e 三元组的 RGB 颜色，则可以按原样使用 transition3 函数。然而，通过 HSV 色彩空间会产生更“自然”的过渡。因此，考虑到转换函数(无耻地从 Python colorsys 模块中窃取并转换为伪代码:):

function rgb_to_hsv(r, g, b):
    maxc= max(r, g, b)
    minc= min(r, g, b)
    v= maxc
    if minc == maxc then return (0, 0, v)
    diff= maxc - minc
    s= diff / maxc
    rc= (maxc - r) / diff
    gc= (maxc - g) / diff
    bc= (maxc - b) / diff
    if r == maxc then
        h= bc - gc
    else if g == maxc then
        h= 2.0 + rc - bc
    else
        h = 4.0 + gc - rc
    h = (h / 6.0) % 1.0 //comment: this calculates only the fractional part of h/6
    return (h, s, v)

function hsv_to_rgb(h, s, v):
    if s == 0.0 then return (v, v, v)
    i= int(floor(h*6.0)) //comment: floor() should drop the fractional part
    f= (h*6.0) - i
    p= v*(1.0 - s)
    q= v*(1.0 - s*f)
    t= v*(1.0 - s*(1.0 - f))
    if i mod 6 == 0 then return v, t, p
    if i == 1 then return q, v, p
    if i == 2 then return p, v, t
    if i == 3 then return p, q, v
    if i == 4 then return t, p, v
    if i == 5 then return v, p, q
    //comment: 0 <= i <= 6, so we never come here

，您可以使用如下代码:

start_triplet= rgb_to_hsv(0, 255, 0) //comment: green converted to HSV
end_triplet= rgb_to_hsv(255, 0, 0) //comment: accordingly for red

maximum= 200

… //comment: value is defined somewhere here

rgb_triplet_to_display= hsv_to_rgb(transition3(value, maximum, start_triplet, end_triplet))