python - 在 Python 中没有 float 学的 HSV 到 RGB(和返回)

Question

有人知道不依赖于任何外部模块的将 HSV 颜色转换为 RGB(反之亦然)的良好 python 算法吗？我正在编写一些动画生成代码并希望支持 HSV 色彩空间，但它在 Raspberry Pi 上运行并且我试图避免任何 float 。

Answer 1

本站here带您完成这些步骤，包括如何使用整数除法。这是那里描述的 RGB 到 HSV 函数的 python 端口

def RGB_2_HSV(RGB):
    ''' Converts an integer RGB tuple (value range from 0 to 255) to an HSV tuple '''

    # Unpack the tuple for readability
    R, G, B = RGB

    # Compute the H value by finding the maximum of the RGB values
    RGB_Max = max(RGB)
    RGB_Min = min(RGB)

    # Compute the value
    V = RGB_Max;
    if V == 0:
        H = S = 0
        return (H,S,V)


    # Compute the saturation value
    S = 255 * (RGB_Max - RGB_Min) // V

    if S == 0:
        H = 0
        return (H, S, V)

    # Compute the Hue
    if RGB_Max == R:
        H = 0 + 43*(G - B)//(RGB_Max - RGB_Min)
    elif RGB_Max == G:
        H = 85 + 43*(B - R)//(RGB_Max - RGB_Min)
    else: # RGB_MAX == B
        H = 171 + 43*(R - G)//(RGB_Max - RGB_Min)

    return (H, S, V)

与 colorsys 函数相比，它给出了正确的结果

import colorsys
RGB = (127, 127, 127)

Converted_2_HSV = RGB_2_HSV(RGB)
Verify_RGB_2_HSV = colorsys.rgb_to_hsv(RGB[0], RGB[1], RGB[2])

print Converted_2_HSV
>>> (0, 0, 127)

print Verify_RGB_2_HSV # multiplied by 255 to bring it into the same scale
>>> (0.0, 0.0, 127.5)

你可以检查输出实际上仍然是一个整数

type(Converted_2_HSV[0])
>>> <type 'int'>

现在是反向功能。原出处可查here ，这里是 Python 端口。

def HSV_2_RGB(HSV):
    ''' Converts an integer HSV tuple (value range from 0 to 255) to an RGB tuple '''

    # Unpack the HSV tuple for readability
    H, S, V = HSV

    # Check if the color is Grayscale
    if S == 0:
        R = V
        G = V
        B = V
        return (R, G, B)

    # Make hue 0-5
    region = H // 43;

    # Find remainder part, make it from 0-255
    remainder = (H - (region * 43)) * 6; 

    # Calculate temp vars, doing integer multiplication
    P = (V * (255 - S)) >> 8;
    Q = (V * (255 - ((S * remainder) >> 8))) >> 8;
    T = (V * (255 - ((S * (255 - remainder)) >> 8))) >> 8;


    # Assign temp vars based on color cone region
    if region == 0:
        R = V
        G = T
        B = P
    
    elif region == 1:
        R = Q; 
        G = V; 
        B = P;

    elif region == 2:
        R = P; 
        G = V; 
        B = T;

    elif region == 3:
        R = P; 
        G = Q; 
        B = V;

    elif region == 4:
        R = T; 
        G = P; 
        B = V;

    else: 
        R = V; 
        G = P; 
        B = Q;


    return (R, G, B)

并且我们可以像之前一样验证结果

interger_HSV = (127, 127, 127)
Converted_2_RGB = HSV_2_RGB(interger_HSV)
Verify_HSV_2_RGB = colorsys.hsv_to_rgb(0.5, 0.5, 0.5)

print Converted_2_RGB
>>> (63, 127, 124)

print type(Converted_2_RGB[0])
>>> <type 'int'>

print Verify_HSV_2_RGB # multiplied these by 255 so they are on the same scale
>>> (63.75, 127.5, 127.5)

整数运算确实会引入一些错误，但是根据应用程序的不同，这些错误可能没问题。