【python图像处理】gif动态图的解析与合成

gif动态图是在现在已经司空见惯，朋友圈里也经常是一言不合就斗图。这里，就介绍下如何使用python来解析和生成gif图像。

一、gif动态图的合成

如下图，是一个gif动态图。

gif动态图的解析可以使用PIL图像模块即可，具体代码如下：

#-*- coding: UTF-8 -*-  

import os
from PIL import Image

def analyseImage(path):
    
    Pre-process pass over the image to determine the mode (full or additive).
    Necessary as assessing single frames isnt reliable. Need to know the mode 
    before processing all frames.
    
    im = Image.open(path)
    results = {
        size: im.size,
        mode: full,
    }
    try:
        while True:
            if im.tile:
                tile = im.tile[0]
                update_region = tile[1]
                update_region_dimensions = update_region[2:]
                if update_region_dimensions != im.size:
                    results[mode] = partial
                    break
            im.seek(im.tell() + 1)
    except EOFError:
        pass
    return results


def processImage(path):
    
    Iterate the GIF, extracting each frame.
    
    mode = analyseImage(path)[mode]
    
    im = Image.open(path)

    i = 0
    p = im.getpalette()
    last_frame = im.convert(RGBA)
    
    try:
        while True:
            print "saving %s (%s) frame %d, %s %s" % (path, mode, i, im.size, im.tile)
            
            
            If the GIF uses local colour tables, each frame will have its own palette.
            If not, we need to apply the global palette to the new frame.
            
            if not im.getpalette():
                im.putpalette(p)
            
            new_frame = Image.new(RGBA, im.size)
            
            
            Is this file a "partial"-mode GIF where frames update a region of a different size to the entire image?
            If so, we need to construct the new frame by pasting it on top of the preceding frames.
            
            if mode == partial:
                new_frame.paste(last_frame)
            
            new_frame.paste(im, (0,0), im.convert(RGBA))
            new_frame.save(%s-%d.png % (.join(os.path.basename(path).split(.)[:-1]), i), PNG)

            i += 1
            last_frame = new_frame
            im.seek(im.tell() + 1)
    except EOFError:
        pass



def main():
    processImage(test_gif.gif)
    

if __name__ == "__main__":
    main()

解析结果如下，由此可见改动态图实际上是由14张相同分辨率的静态图组合而成

二、gif动态图的合成

gif图像的合成，使用imageio库（）

代码如下：

#-*- coding: UTF-8 -*-  

import imageio

def create_gif(image_list, gif_name):

    frames = []
    for image_name in image_list:
        frames.append(imageio.imread(image_name))
    # Save them as frames into a gif 
    imageio.mimsave(gif_name, frames, GIF, duration = 0.1)

    return

def main():
    image_list = [test_gif-0.png, test_gif-2.png, test_gif-4.png, 
                  test_gif-6.png, test_gif-8.png, test_gif-10.png]
    gif_name = created_gif.gif
    create_gif(image_list, gif_name)

if __name__ == "__main__":
    main()

2017.08.24