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本文实例讲述了Python实现PS图像调整颜色梯度效果。分享给大家供大家参考，具体如下：

这里用 Python 实现 PS 中的色彩图，可以看到颜色的各种渐变，具体的效果可以参考附录说明

和之前的程序相比，这里利用矩阵的运算替代了 for 循环，提升了运行的效率。

import numpy as np
import matplotlib.pyplot as plt
from skimage import io
import numpy.matlib
from skimage import img_as_float
file_name='D:/Visual Effects/PS Algorithm/4.jpg';
img=io.imread(file_name)
img = img_as_float(img)
row, col, channel = img.shape
rNW = 0.5
rNE = 1.0
rSW = 1.0
rSE = 0.0
gNW = 0.0
gNE = 0.5
gSW = 0.0
gSE = 1.0
bNW = 1.0
bNE = 0.0
bSW = 1.0
bSE = 0.0
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)
fx = x_mask * 1.0 / col
fy = y_mask * 1.0 / row
p = rNW + (rNE - rNW) * fx
q = rSW + (rSE - rSW) * fx
r = ( p + (q - p) * fy )
r[r<0] = 0
r[r>1] =1
p = gNW + (gNE - gNW) * fx
q = gSW + (gSE - gSW) * fx
g = ( p + (q - p) * fy )
g[g<0] = 0
g[g>1] =1
p = bNW + (bNE - bNW) * fx
q = bSW + (bSE - bSW) * fx
b = ( p + (q - p) * fy )
b[b<0] = 0.0
b[b>1] = 1.0
img[:, :, 0] = r
img[:, :, 1] = g
img[:, :, 2] = b
plt.figure(1)
plt.imshow(img)
plt.axis('off');
plt.show();

附录：PS 色调— —颜色梯度

  clc;
  clear all;
  close all;
  addpath('E:\PhotoShop Algortihm\Image Processing\PS Algorithm');
  I=imread('4.jpg');
  Image=double(I)/255;
  [height, width, depth]=size(Image);
  rNW=1.0;   gNW=0.0;  bNW=0.0;
  rNE=1.0;   gNE=1.0;  bNE=0.0;
  rSW=0.0;   gSW=0;   bSW=1.0;
  rSE=0.0;   gSE=1.0;  bSE=0.0;
  Img_new=Image;
  for ii=1:height
    for jj=1:width
      fx = jj / width;
      fy = ii / height;
      p = rNW + (rNE - rNW) * fx;
      q = rSW + (rSE - rSW) * fx;
      r = ( p + (q - p) * fy );
      r = min(max(r, 0), 1);
      p = gNW + (gNE - gNW) * fx;
      q = gSW + (gSE - gSW) * fx;
      g = ( p + (q - p) * fy );
      g = min(max(g, 0) ,1);
      p = bNW + (bNE - bNW) * fx;
      q = bSW + (bSE - bSW) * fx;
      b = ( p + (q - p) * fy );
      b = min(max(b, 0), 1);
      Img_new(ii, jj, 1)=r;
      Img_new(ii, jj, 2)=g;
      Img_new(ii, jj, 3)=b;
    end  
  end
  imshow(Img_new);
  imwrite(Img_new, 'out.jpg');

参考来源：http://www.jhlabs.com/index.html

本例Python运行效果图：

原图：