问题

下图是可见光的波谱，编写程序绘制该图像。

分析

根据下图公式，计算各段波长的颜色，保存在列表中。遍历每种颜色，利用matplotlib.pyplot依次绘制线段并填满区间，打表出结果。

代码

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import numpy as np
import matplotlib.pyplot as plt


def CIE_RGB():
    rgb = np.zeros([1000,1000,3])
    r = np.arange(0,1,0.001)
    r,g = np.meshgrid(r,r)
    rgb[:,:,0] = r
    rgb[:,:,1] = g
    rgb[:,:,2] = 1-r-g
    over = rgb[:,:,2]<0
    rgb[over,:]=[1,1,1]

    #将色品转化成RGB
    maxVal = np.max(rgb,2)
    for i in [0,1,2]:
        rgb[:,:,i] /= maxVal
    #rgb[rgb<0]=0

    ax = plt.gca()
    ax.imshow(rgb)
    ax.invert_yaxis()    #plt显示图片时y轴从上到下，所以反置
    # 坐标映射
    plt.xticks(range(0,1001,200),['0','0.2','0.4','0.6','0.8','1'])
    plt.yticks(range(0,1001,200),['0','0.2','0.4','0.6','0.8','1'])
    plt.show()

#dWave为波长；maxPix为最大值；gamma为参数
def getRGB(dWave,maxPix=1,gamma=1):
    waveArea = [380,440,490,510,580,645,780]
    minusWave = [0,440,440,510,510,645,780]
    deltWave = [1,60,50,20,70,65,35]
    for p in range(len(waveArea)):
        if dWave<waveArea[p]:
            break

    pVar = abs(minusWave[p]-dWave)/deltWave[p]
    rgbs = [[0,0,0],[pVar,0,1],[0,pVar,1],[0,1,pVar],
            [pVar,1,0],[1,pVar,0],[1,0,0],[0,0,0]]
    
    #在光谱边缘处颜色变暗
    if (dWave>=380) & (dWave<420):
        alpha = 0.3+0.7*(dWave-380)/(420-380)
    elif (dWave>=420) & (dWave<701):
        alpha = 1.0
    elif (dWave>=701) & (dWave<780):
        alpha = 0.3+0.7*(780-dWave)/(780-700)
    else:
        alpha = 0       #非可见区

    return [maxPix*(c*alpha)**gamma for c in rgbs[p]]

def drawSpec():
    pic = np.zeros([100,360,3])
    rgb = [getRGB(d) for d in range(400,760)]
    pic = pic+rgb
    plt.imshow(pic)
    plt.yticks([])      #隐藏y坐标轴
    plt.xticks(range(0,360,50),['400','450','500','550','600','650','700','750'])
    plt.show()

drawSpec()

结果