Pillow

目录

• Basics
  • Read image
  • show information
  • convert format
  • resize
  • thumbnail
  • blend
  • rotate
• modify image
• Gif
  • gif from images
  • operations on gif

本篇博客简单介绍pillow，作为学习的记录。更多信息请前往PIL documentation

pillow是python的一个标准图像处理库，相比于opencv，它像是一个玩具，但是已经能够满足一些基本的使用。

与此相关的：opencv, PhotoShop

Basics

Read image

from PIL import Image
im = Image.open('image/animate2.png')
im.show()
print(im.size)

show information

print(im.info)
print(im.mode)
print(im.format)

RGBA是一种颜色格式，alpha通道表示不透明度。例如：logo图标通常是png图片，如果转换为jpg图片会有黑边。

convert format

img_jpg = im.convert('RGB')
img_jpg.save('image/animate2_jpg.jpg')
im.show()
img_jpg.show()

RGB to RGBA 同理

resize

white = Image.open('image/inwhite1.jpg')
white_resize = white.resize((500,500))
white_resize.show()

关于resize这里有一些讨论知乎, GitHub。总结就是PIL和opencv的像素点选择有差异，所以会导致图像有细微差别。如果你只是简单的使用不需要关心这一点，如果你在做cv就需要格外注意。

thumbnail

white.thumbnail((150,150))
white.show()
print(white.size)
white.save('image/thumbnail.jpg')

使用resize可能会变形，有时候我们不希望这么做，那就可以选择thumbnail，它会进行等比例缩放。

blend

white1 = Image.open('image/inwhite1.jpg')
white2 = Image.open('image/inwhite2.jpg')
white1 = white1.resize(white2.size)
blended = Image.blend(white1, white2, 0.35)
blended.show()

对于在上例中blend的操作可以理解为blended = white1*0.65+white*0.35

rotate

nico = Image.open('image/nike.png')
nico_out = nico.rotate(-45, translate=(0,-25), fillcolor='blue')
nico_out.show()
nico_out.save('image/nike_rotate.png')

modify image

这里仅给出一个例子：为图片添加水印(water mask)
选择字体（可选）

from PIL import ImageFont

font1 = ImageFont.truetype('C:/Windows/Fonts/Inkfree.ttf',size=100)
font2 = ImageFont.truetype('C:/Windows/Fonts/fengxingti.ttf',size=100) #风行体
font3 = ImageFont.truetype('C:/Windows/Fonts/shiguangshaonv.ttf',size=100) #时光少女
font = font2

from PIL import ImageDraw
def creating_watermark(im,text,font=font):
    im_rgba = im.convert('RGBA')
    im_text_canvas = Image.new("RGBA",im_rgba.size, (255,255,255,0))
    
    draw = ImageDraw.Draw(im_text_canvas)
    text_x_width, text_y_height = draw.textsize(text, font=font)
    

    text_xy = (im_rgba.size[0] - 2 * text_x_width, im_rgba.size[1] - 2 * text_y_height)
    
    draw.text(text_xy, text, font=font, fill=(255,0,0,128))
    im_text = Image.alpha_composite(im_rgba, im_text_canvas)
    
    return im_text

blended_watermark = creating_watermark(blended, 'love',font=font3)
blended_watermark.show()
blended_watermark.save('image/blended3.png')

Gif

opencv不支持处理gif格式的文件，但是pillow和imageio可以。

gif from images

import os

def jpg_to_gif(jpg_path, gif_name):
    frames = []
    
    for i in range(11):
        path = os.path.join(jpg_path, 'girl{}.jpg'.format(i))
        frame = Image.open(path)
        frame.thumbnail((1000,1000))
        frames.append(frame)
        
    frames[0].save(gif_name, save_all=True, append_images=frames[1:], format='GIF', duration=1000, loop=0, disposal=2)

jpg_to_gif('./image/', './video/scaled_girls.gif')

效果展示

图片来源于https://www.vmgirls.com/，侵删。

imageio也可以处理gif

import imageio
def create_gif(image_list, gif_name, duration=0.35):
    frames = []
    for image_name in image_list:
        frames.append(imageio.imread(image_name))
    imageio.mimsave(gif_name, frames, 'GIF', duration=duration)
    return

image_list = ['image/girl{}.jpg'.format(i) for i in range(11)]
create_gif(image_list, './video/girls_by_imageio.gif')

operations on gif

reference:PIL fork

girls = Image.open("video/scaled_girls.gif")
type(girls)
# PIL.GifImagePlugin.GifImageFile

GifImageFile继承自ImageFile，有如下几种属性

• n_frames
• is_animated
• seek()
• tell()

example:

cropped_images = []
crop_box = (250, 250, 500, 700)
for index in range(girls.n_frames):
    girls.seek(index)
    cropped = girls.crop(crop_box)
    cropped_images.append(cropped)

cropped_images[0].save(
    'video/sample_cropped.gif',
    save_all=True,
    append_images=cropped_images[1:],
    duration=500,
    loop=0,
)