具有 alpha channel 背景的 Python 文本

Question

我正在使用 Python 2.7.3 和 PIL/Pillow，并希望在另存为 png 的 alpha_channel 背景上创建文本(具有不透明度)。这是我的代码，它不完全符合我的期望:

from PIL import Image
from PIL import ImageDraw
from PIL import ImageFont
from PIL import ImageEnhance

width=854
height=480
opacity=0.8
text='copyright'
filename = 'result.png'
black = (0,0,0)
white = (255,255,255)

font = ImageFont.truetype('verdana.ttf',15)
wm = Image.new('RGBA',(width,height),white)
im = Image.new('L',(width,height),0)

draw = ImageDraw.Draw(wm)
w,h = draw.textsize(text, font)
draw.text(((width-w)/2,(height-h)/2),text,white,font)

en = ImageEnhance.Brightness(wm)
#en.putalpha(mask)
mask = en.enhance(1-opacity)
im.paste(wm,(25,25),mask)

im.save(filename)

结果:

下面的代码是我要找的，但是背景完全透明/alpha_channel:

import PIL
from PIL import ImageFont
from PIL import Image
from PIL import ImageDraw

width = 854
height = 480
black = (0,0,0)
text = "copyright"
white = (255,255,255)
font = ImageFont.truetype("Arial.ttf",40)
img = Image.new("RGBA", (width,height),white)
draw = ImageDraw.Draw(img)
w, h = draw.textsize(text, font)
draw.text(((width-w)/2,(height-h)/2),text,black,font=font)
draw = ImageDraw.Draw(img)
#img.putalpha
img.save("result.png")
#img.show

结果:

Answer 1

问题是 wm 与文本颜色相同，所以如果在上面绘制文本，您将看不到任何东西。将 wm 的颜色更改为透明，就像我在下面所做的那样(并在宽度、高度和不透明度初始化后删除逗号):

from PIL import Image
from PIL import ImageDraw
from PIL import ImageFont
from PIL import ImageEnhance

width=854
height=480
opacity=0.8
text='copyright'
filename = 'result.png'
black = (0,0,0)
white = (255,255,255)
transparent = (0,0,0,0)

font = ImageFont.truetype('verdana.ttf',15)
wm = Image.new('RGBA',(width,height),transparent)
im = Image.new('RGBA',(width,height),transparent) # Change this line too.

draw = ImageDraw.Draw(wm)
w,h = draw.textsize(text, font)
draw.text(((width-w)/2,(height-h)/2),text,white,font)

en = ImageEnhance.Brightness(wm)
#en.putalpha(mask)
mask = en.enhance(1-opacity)
im.paste(wm,(25,25),mask)

im.save(filename)