我正在尝试使用PIL来合成一些航拍图像并遇到麻烦。我使用PIL加载this image这段代码:
composite = Image.new('RGBA', (256, 256))
url = 'http://...'
resp = requests.get(url)
content = StringIO(resp.content)
image = Image.open(content)
composite.paste(image, (0, 0), image)
当我调用composite.paste()
时,PIL给出了错误“ValueError:bad transparency mask”。当我打印image.mode
时,确实只是RGB
而不是预期的RGBA
(paste()
要求的)。
我下载的PNG上的Alpha通道在哪里?
答案 0 :(得分:4)
以下代码对我有用:
from PIL import Image
import requests
import StringIO
url = "https://gis.apfo.usda.gov/arcgis/rest/services/NAIP/Tennessee_2016_60cm/ImageServer/exportImage?bbox=-87.1875,34.3071438563,-84.375,36.5978891331&bboxSR=4326&size=256,256&imageSR=102113&transparent=true&format=png&f=image"
resp = requests.get(url)
content = StringIO.StringIO(resp.content)
image = Image.open(content)
image = image.convert('RGBA')
composite = Image.new("RGBA", image.size, (255,255,255,0))
composite.paste(image )
答案 1 :(得分:0)
据我所见,图片为RGBA
。看看
$ convert exportImage.png -verbose info
Image: exportImage.png
Format: PNG (Portable Network Graphics)
Mime type: image/png
Class: DirectClass
Geometry: 256x256+0+0
Units: Undefined
Type: TrueColorAlpha
Endianess: Undefined
Colorspace: sRGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
alpha: 1-bit
Channel statistics:
Pixels: 65536
Red:
min: 39 (0.152941)
max: 253 (0.992157)
mean: 133.019 (0.521641)
standard deviation: 75.3931 (0.295659)
kurtosis: -1.05835
skewness: 0.86831
Green:
min: 59 (0.231373)
max: 253 (0.992157)
mean: 152.489 (0.597998)
standard deviation: 62.9948 (0.247038)
kurtosis: -1.03932
skewness: 0.87929
Blue:
min: 39 (0.152941)
max: 253 (0.992157)
mean: 135.817 (0.532617)
standard deviation: 72.8752 (0.285785)
kurtosis: -1.01856
skewness: 0.929917
Alpha:
min: 0 (0)
max: 255 (1)
mean: 185.273 (0.726562)
standard deviation: 113.659 (0.445723)
kurtosis: -0.966513
skewness: 1.01661
Image statistics:
Overall:
min: 0 (0)
max: 255 (1)
mean: 122.763 (0.481424)
standard deviation: 83.4891 (0.327408)
kurtosis: -0.482848
skewness: 0.432253
Alpha: srgba(253,253,253,0) #FDFDFD00 --------> (1)
等等。
现在,让我们使用PIL
和Python 3加载图像:
from PIL import Image
from io import BytesIO
url = "..."
resp = requests.get(url)
cont = BytesIO(resp.content)
img = Image.open(cont)
comp = Image.new('RGBA', (256, 256), (255, 255, 255, 0)) # 0 for transparency
comp.paste(img, (0, 0))
由于上述图像统计中的eqn(1),我们在制作新图像时也要给0
。