如何使用 PIL 根据 RGB 中的发光去除像素？

Question

我正在尝试编写一个故障艺术程序，让我可以让图片有点像沙子一样掉下来，我让它适用于灰度 (L)。我正在尝试将其转换为颜色，但我无法让此代码正常工作。这是我的颜色

#! /usr/bin/python
from PIL import Image
from random import randint

# Sorts img kinda randomly
source = Image.open("test.jpg")
threshold = 150

img = source.load()

blackandwhite = source.convert("L").load()

canvas = Image.new("RGB", source.size)

newimg = canvas.load()
count = source.size[0]

print (source.format)
print (source.size)
print (source.mode)
print ("Threshold: ", threshold)
print ("============================================")

counter = 0 #counter
# do the loop twice because we want to make em fall!
counter = 0
for i in range(0, source.size[0]-1): # loop through every x value
    vert_list = [] #list of this column
    for pix in range(0, source.size[1]-1): #make a list of the column from the b&w img
        color = blackandwhite[i, pix] #for being in color ^^
        vert_list.append( color )

    counter += 1
    if counter % 10 == 0:
        print(counter, "/", count)
    #now remove all pixels brighter than the threshold

    color_vert_list = []
    for x in range(0, len(vert_list)-1):
        if vert_list[x] < threshold:
            color_vert_list.append(img[i, pix]) #add colors darker than something to the color list

    top_spacing = source.size[1] - len(color_vert_list) #height
    for pixel in range(0, len(color_vert_list)):
        newimg[i,pixel + top_spacing] = color_vert_list[pixel] #add em


canvas.save("fall.png") #save

这是相同的黑白代码

#! /usr/bin/python
from PIL import Image
from random import randint

# Sorts img kinda randomly
source = Image.open("test.jpg")
threshold = 150

img = source.load()

blackandwhite = source.convert("L").load()

canvas = Image.new("L", source.size)

newimg = canvas.load()
count = source.size[0]

print (source.format)
print (source.size)
print (source.mode)
print ("Threshold: ", threshold)
print ("============================================")

counter = 0 #counter
# do the loop twice because we want to make em fall!
counter = 0
for i in range(0, source.size[0]-1): # loop through every x value
    vert_list = [] #list of this column
    for pix in range(0, source.size[1]-1): #make a list of the column from the b&w img
        color = blackandwhite[i, pix] #for being in color ^^
        vert_list.append( color )

    counter += 1
    if counter % 10 == 0:
        print(counter, "/", count)
    #now remove all pixels brighter than the threshold
    vert_list[:] = (x for x in vert_list if threshold > x)

    top_spacing = source.size[1] - len(vert_list) #height
    for pixel in range(0, len(vert_list)):
        newimg[i,pixel + top_spacing] = vert_list[pixel]


canvas.save("fall.png")

Answer 1

看起来您的问题是您正试图从灰度值的索引中取回颜色值（您已丢弃），但是当您已经丢弃以前的灰度值时，这将不起作用并且索引不再匹配。

那么让我们重新开始吧。与其保留灰度顶点列表和颜色顶点列表并尝试将它们匹配，不如保留（灰度，颜色）对的列表。像这样：

for pix in range(0, source.size[1]-1): #make a list of the column from the b&w img
    grey = blackandwhite[i, pix]
    color = img[i, pix]
    vert_list.append((grey, color))

现在，您只需更改过滤器以使用对中的灰度值：

vert_list[:] = (x for x in vert_list if threshold > x[0])

... 并更改 newimg 分配以使用该对中的颜色值：

newimg[i,pixel + top_spacing] = vert_list[pixel][1]

并且（除了更改canvas 的模式，您已经做对了），这就是您需要做的所有事情。

我已经发布了一个完整的实现here（在三个更改的行上有 cmets）。