DIY 雪花特效（一）

用户6021899

发布于 2020-03-23 15:06:09

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发布于 2020-03-23 15:06:09

文章被收录于专栏：Python编程 pyqt matplotlibPython编程 pyqt matplotlib

对任意一张图片，我们可以用代码给它加点雪花特效，做成动图。

原图：

加特效后：

首先我们需要雪花的图片，比如下面这张（其实这张有点不太真实，不过无妨，我只是拿它来做演示）。

做图像分割后我们就得到了16张雪花的图片（其实一张也足够）：

用pickle模块将它们保存到本地，以供后续调用。

万事俱备，下面我们来给原图加上雪花。主要代码如下：

"""
Created on Sat Dec 15 10:15:18 2019
@author: wangsp
"""
import numpy as np
from matplotlib import pyplot as plt
import cv2
import pickle
import imageio
from random import randint,normalvariate

def create_gif(frames, gif_name,duration=0.3,reverse=False):
    if reverse: frames.sort(reverse=True)
    imageio.mimsave(gif_name,frames,"GIF",duration=duration)
    return frames
    
BG = plt.imread("plum.jpg")#加载背景图
H,W,C = BG.shape
frame  = BG.astype(np.uint16)
frames = []

class Snow:
    def __init__(self,type_,x0,y0,speed0,scale):
        self.scale = scale
        #type_ : from 1 to 16
        self.data = self.get_snow(type_)
        self.x = x0
        self.y = y0
        self.speed = speed0
        
    def get_snow(self, type_):
        with open("snow%d.data"%type_,"rb") as f:
            data = pickle.load(f)
            #缩小一点
            self.h,self.w = data.shape
            data = cv2.resize(data,(int(self.h*self.scale),int(self.w*self.scale)))
            
            self.h,self.w = data.shape
            snow = np.zeros((self.h,self.w,3),dtype = np.uint8)
            snow[data==1] = np.array([255,255,255])
        return snow
        
    def update(self): #动画效果
        global frames, frame
        
        c = self.w%2 #compensation, 偶数0， 奇数1
        #restore
        if self.y < self.h:
            frame[0:self.y, self.x-int(self.w/2):self.x+int(self.w/2)+c] = BG[0:self.y,self.x-int(self.w/2):self.x+int(self.w/2)+c]
        elif self.y < H:
            frame[self.y-self.h:self.y, self.x-int(self.w/2):self.x+int(self.w/2)+c]= BG[self.y-self.h:self.y,self.x-int(self.w/2):self.x+int(self.w/2)+c]
        elif self.y < H + self.h:
            frame[self.y-self.h:, self.x-int(self.w/2):self.x+int(self.w/2)+c] = BG[self.y-self.h:,self.x-int(self.w/2):self.x+int(self.w/2)+c]
        else:
            pass
        
        self.x += 0
        self.y += self.speed
        if self.y < self.h:
            frame[0:self.y, self.x-int(self.w/2):self.x+int(self.w/2)+c] += self.data[self.h-self.y:,:]
        elif self.y < H:
            frame[self.y-self.h:self.y, self.x-int(self.w/2):self.x+int(self.w/2)+c] += self.data
        elif self.y < H + self.h:
            frame[self.y-self.h:, self.x-int(self.w/2):self.x+int(self.w/2)+c] += self.data[:H-(self.y-self.h),:]
        else:
            self.y = 0
        frame[frame>255] = 255
       

n_snows = randint(100,120) # include both ends
snows  = []
for i in range(n_snows):
    type_ = randint(1,16) #include both ends
    x0 = randint(10,W-10)
    y0 = randint(0,H)
    speed = int(normalvariate(3,0.5))
    scale = normalvariate(0.02,0.005)
    snow = Snow(type_,x0, y0, speed,scale)
    snows.append(snow)
              
n_frames = 30 #因为公众号只能穿5M以下的图，所以帧数弄少一点
for n in range(n_frames):
    for i in range(n_snows):
        snows[i].update()
    frames.append(frame.astype(np.uint8))
                
create_gif(frames,"snow_plum_5M.gif",0.01) #创建GIF

至此，我们可以给小倩下场雪：