Pillow常用方法汇总

• 打开图片
  打开一张图片是一个很快的操作，和图片的尺寸以及压缩方式无关，打开的时候只读取文件header来获取文件格式、模式、尺寸等信息

from PIL import Image
im = Image.open("hopper.ppm")

with open("hopper.ppm", "rb") as fp:
    im = Image.open(fp)

# read from binary data
import io
im = Image.open(io.BytesIO(buffer))

# read from url
from PIL import Image
from urllib.request import urlopen
url = "https://python-pillow.org/images/pillow-logo.png"
img = Image.open(urlopen(url))

• 显示图片格式

>>> im.format
PPM

• 图片尺寸

>>> im.size
(512,512)

• 图片模式

>>> im.mode
# L for greyscale,RGB for true color images,CMYK for pre-press images
RGB

• 展示图片

>>> im.show()

• 保存图片

>>> im.save("hopper.jpg")

• 裁切图片
  裁切需要使用到一个四元组$(left,up,right,bottom)$,图片的左上坐标是$(0,0)$

box = (100, 100, 400, 400)
region = im.crop(box)

• 将一张图片粘贴到另一张图片上
  此时被粘贴的图片需要大小和box吻合

region = region.transpose(Image.Transpose.ROTATE_180)
im.paste(region, box)

• 改变RGB图像通道的位置

r, g, b = im.split()
im = Image.merge("RGB", (b, g, r))

• 图片缩放，旋转

out = im.resize((128, 128))
out = im.rotate(45) # degrees counter-clockwise
out = im.transpose(Image.Transpose.FLIP_LEFT_RIGHT)
out = im.transpose(Image.Transpose.FLIP_TOP_BOTTOM)
out = im.transpose(Image.Transpose.ROTATE_90)
out = im.transpose(Image.Transpose.ROTATE_180)
out = im.transpose(Image.Transpose.ROTATE_270)

• 图片模式转换

from PIL import Image

with Image.open("hopper.ppm") as im:
    im = im.convert("L")

• 图片增强

from PIL import ImageFilter
out = im.filter(ImageFilter.DETAIL)

from PIL import ImageEnhance

enh = ImageEnhance.Contrast(im)
enh.enhance(1.3).show("30% more contrast")

• 图片阵列操作

# multiply each pixel by 1.2
out = im.point(lambda i: i * 1.2)

# split the image into individual bands
source = im.split()

R, G, B = 0, 1, 2

# select regions where red is less than 100
mask = source[R].point(lambda i: i < 100 and 255)

# process the green band
out = source[G].point(lambda i: i * 0.7)

# paste the processed band back, but only where red was < 100
source[G].paste(out, None, mask)

# build a new multiband image
im = Image.merge(im.mode, source)

• 动图操作

from PIL import Image

with Image.open("animation.gif") as im:
    im.seek(1)  # skip to the second frame

    try:
        while 1:
            im.seek(im.tell() + 1)
            # do something to im
    except EOFError:
        pass  # end of sequence

from PIL import ImageSequence
for frame in ImageSequence.Iterator(im):
    # ...do something to frame...