python练习 双线性插值对图像进行伸缩变换

import numpy as np
import cv2
##双线性插值
def resize(src,dstsize):#输入src 和size
if src.ndim==3:
dstsize.append(3)
dst=np.array(np.zeros(dstsize),src.dtype)
factory=float(np.size(src,0))/dstsize[0]
factorx=float(np.size(src,1))/dstsize[1]
print 'factory',factory,'factorx',factorx
srcheight=np.size(src,0)
srcwidth=np.size(src,1)
print 'srcwidth',srcwidth,'srcheight',srcheight
for i in range(dstsize[0]):
for j in range(dstsize[1]):
y=float(i)*factory
x=float(j)*factorx
if y+1>srcheight:  #越界判断
y-=1
if x+1>srcwidth:
x-=1
cy=np.ceil(y)
fy=cy-1
cx=np.ceil(x)
fx=cx-1
w1=(cx-x)*(cy-y)
w2=(x-fx)*(cy-y)
w3=(cx-x)*(y-fy)
w4=(x-fx)*(y-fy)
if (x-np.floor(x)>1e-6 or y-np.floor(y)>1e-6):
t=src[fy,fx]*w1+src[fy,cx]*w2+src[cy,fx]*w3+src[cy,cx]*w4
t=np.ubyte(np.floor(t))
dst[i,j]=t
#print t
else:   	#映射到原图像刚好是整数的坐标
dst[i,j]=(src[y,x])
# print src[i,j]
return dst

def test1():
img=cv2.imread('cat.jpg',1)
print np.size(img,0)
dst=resize(img,[100,100])
cv2.imshow('dst',dst)
cv2.imshow('src',img)
cv2.waitKey()
cv2.destroyAllWindows()

if __name__=='__main__':
test1()