本文实例讲述了Python实现PS滤镜特效之扇形变换效果。分享给大家供大家参考，具体如下：

这里用 Python 实现 PS 滤镜中的一种几何变换特效，称为扇形变换，将图像扭曲成一个扇形，具体的算法原理和效果图可以参考附录说明

import numpy as np

from skimage import img_as_float

import matplotlib.pyplot as plt

from skimage import io

import math

import numpy.matlib

file_name2='D:/Visual Effects/PS Algorithm/4.jpg'

img=io.imread(file_name2)

img = img_as_float(img)

# control the radius of the inner circle

radius = 150

# control the distance between the inner circle and outer circle

high = 200

angle = 0

spreadAngle = math.pi

# set the center of the circle, proportion of the image size

centerX = 0.5

centerY = 1.0

row, col, channel = img.shape

icenterX = col * centerX

icenterY = row * centerY

img_out = img * 0

xx = np.arange (col)

yy = np.arange (row)

x_mask = numpy.matlib.repmat (xx, row, 1)

y_mask = numpy.matlib.repmat (yy, col, 1)

y_mask = np.transpose(y_mask)

xx_dif = x_mask - icenterX

yy_dif = y_mask - icenterY

theta = np.arctan2(-yy_dif, -xx_dif+0.0001)

r = np.sqrt(xx_dif*xx_dif + yy_dif * yy_dif)

theta = np.mod(theta, 2 * math.pi)

x1_mask = col * theta/(spreadAngle+0.00001)

y1_mask = row * (1-(r-radius)/(high+0.00001))

'''

mask = x1_mask < 0

x1_mask = x1_mask * (1 - mask)

mask = x1_mask > (col - 1)

x1_mask = x1_mask * (1 - mask) + (x1_mask * 0 + col -2) * mask

mask = y1_mask < 0

y1_mask = y1_mask * (1 - mask)

mask = y1_mask > (row -1)

y1_mask = y1_mask * (1 - mask) + (y1_mask * 0 + row -2) * mask

'''

int_x = np.floor (x1_mask)

int_x = int_x.astype(int)

int_y = np.floor (y1_mask)

int_y = int_y.astype(int)

for ii in range(row):

for jj in range (col):

new_xx = int_x [ii, jj]

new_yy = int_y [ii, jj]

if x1_mask [ii, jj] < 0 or x1_mask [ii, jj] > col -1 :

continue

if y1_mask [ii, jj] < 0 or y1_mask [ii, jj] > row -1 :

continue

img_out[ii, jj, :] = img[new_yy, new_xx, :]

plt.figure (1)

plt.title('www.ddpool.cn')

plt.imshow (img)

plt.axis('off')

plt.figure (2)

plt.title('www.ddpool.cn')

plt.imshow (img_out)

plt.axis('off')

plt.show()

附录：PS 滤镜— —扇形warp

clc;

clear all;

close all;

addpath('E:\PhotoShop Algortihm\Image Processing\PS Algorithm');

I=imread('4.jpg');

I=double(I);

Image=I/255;

[height, width, depth]=size(Image);

% set the parameters

radius = 150; % control the radius of the inner circle

high = 200; % control the distance between the inner circle and outer circle

angle = 0;

spreadAngle=pi;

centerX = 0.5; % set the center of the circle, proportion of the image size

centerY = 1.0;

icenterX=width*centerX;

icenterY=height*centerY;

Image_new=Image*0;

for i=1:height

for j=1:width

dx=j-icenterX;

dy=i-icenterY;

theta=atan2(-dy, -dx)+angle;

r=sqrt(dy*dy+dx*dx);

theta=mod(theta, 2*pi);

x=width * theta/(spreadAngle+0.00001);

y=height * (1-(r-radius)/(high+0.00001));

% % if (x<=1) x=1; end

% % if (x>=width) x=width-1; end;

% % if (y>=height) y=height-1; end;

% % if (y<1) y=1; end;

% %

if (x<=1) continue; end

if (x>=width) continue; end;

if (y>=height) continue; end;

if (y<1) continue; end;

x1=floor(x);

y1=floor(y);

p=x-x1;

q=y-y1;

Image_new(i,j,:)=(1-p)*(1-q)*Image(y1,x1,:)+p*(1-q)*Image(y1,x1+1,:)...

+q*(1-p)*Image(y1+1,x1,:)+p*q*Image(y1+1,x1+1,:);

end

end

imshow(Image_new)

imwrite(Image_new, 'out.jpg');

参考来源：http://www.jhlabs.com/index.html

本例Python运行效果：

原图

效果图

希望本文所述对大家Python程序设计有所帮助。