为了加深理解，写了一些代码测试，在这里记录一下吧：

关于图片的模式问题，之前做过笔记，有“1”，“L”,"P","RGB","RGBA","CMYK',"YCBCr","Note","LAB"等，这几种图片模式有什么区别呢？

#001

from PIL import Image
img1=Image.new("1",(3,3))
data1=img1.getdata()
print(list(data1))
img2=Image.new("L",(3,3))
data2=img2.getdata()
print(list(data2))
img3=Image.new("P",(3,3))
data3=img3.getdata()
print(list(data3))
img4=Image.new("RGB",(3,3))
data4=img4.getdata()
print(list(data4))
img5=Image.new("CMYK",(3,3))
data5=img5.getdata()
print(list(data5))

>>

[0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0]
[(0, 0, 0), (0, 0, 0), (0, 0, 0), (0, 0, 0), (0, 0, 0), (0, 0, 0), (0, 0, 0), (0, 0, 0), (0, 0, 0)]
[(0, 0, 0, 0), (0, 0, 0, 0), (0, 0, 0, 0), (0, 0, 0, 0), (0, 0, 0, 0), (0, 0, 0, 0), (0, 0, 0, 0), (0, 0, 0, 0), (0, 0, 0, 0)]

可以看出"1","L"，“P”模式都是用一位表示颜色值，而"RGB'使用3位表示颜色值，"RGBA","CMYK"等用四位来表示

#002

from PIL import Image
img1=Image.new("1",(3,3),18)
data1=img1.getdata()
print(list(data1))

img1.save("2.png")
img_1=Image.open("2.png")
print(list(img_1.getdata()))

>>

[18, 18, 18, 18, 18, 18, 18, 18, 18]
[255, 255, 255, 255, 255, 255, 255, 255, 255]

之前说"1"模式只有黑白两种颜色，一个像素也是用一位表示，那试着在创建它的时候给它设置一个非黑白色的颜色，结果保存再读取出来的，又自动变成黑色了

#003

from PIL import Image
img1=Image.new("L",(3,3),(30,30,30))
data1=img1.getdata()
print(list(data1))

>>TypeError: function takes exactly 1 argument (3 given)

#004

from PIL import Image
img1=Image.new("RGB",(3,3),(30,30,30))
data1=img1.getdata()
print(list(data1))

img1.save("2.png")
img_1=Image.open("2.png")
print(list(img_1.getdata()))

>>

[(30, 30, 30), (30, 30, 30), (30, 30, 30), (30, 30, 30), (30, 30, 30), (30, 30, 30), (30, 30, 30), (30, 30, 30), (30, 30, 30)]
[(30, 30, 30), (30, 30, 30), (30, 30, 30), (30, 30, 30), (30, 30, 30), (30, 30, 30), (30, 30, 30), (30, 30, 30), (30, 30, 30)]

创建“L”模式时，给它传入一个rgb值报错了，“RGB”模式则可以。

然后，对于RGB模式去亮色转灰色有点好奇，在网上找到很多方法，不明所以，但是有几个公式可以用，其中一个是：

gray=R*0.3+G*0.59+B*0.11，顺便试了一下

#005

from PIL import Image
img1=Image.new("RGB",(100,100),(135,206,235))
#img1.show()
gray=135*0.3+206*0.59+235*0.11
img2=Image.new("RGB",(100,100),(int(gray),int(gray),int(gray)))
print(str(gray))
print(str(int(gray)))
img2.show()

#006

from PIL import Image
img1=Image.open("f:\cat.jpg")
or_data=list(img1.getdata())
#print(or_data)
gr_data=[]
for pix in or_data:
    i=pix[0]*0.3+pix[1]*0.59+pix[2]*0.11
    j=int(i)
    gr_pix=(j,j,j)
    gr_data.append(gr_pix)

gr_img=Image.new("RGB",(img1.size[0],img1.size[1]))
gr_img.putdata(gr_data)
gr_img.show()

转化效果