python实现图像高斯金字塔的示例代码_Python

python实现图像高斯金字塔的示例代码

2021-08-12 00:39我坚信阳光灿烂 Python

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									import cv2

									import numpy as np

									import matplotlib.pyplot as plt

									# Grayscale

									def BGR2GRAY(img):

									  # Grayscale

									  gray = 0.2126 * img[..., 2] + 0.7152 * img[..., 1] + 0.0722 * img[..., 0]

									  return gray

									# Bi-Linear interpolation

									def bl_interpolate(img, ax=1., ay=1.):

									  if len(img.shape) > 2:

									    H, W, C = img.shape

									  else:

									    H, W = img.shape

									    C = 1

									  aH = int(ay * H)

									  aW = int(ax * W)

									  # get position of resized image

									  y = np.arange(aH).repeat(aW).reshape(aW, -1)

									  x = np.tile(np.arange(aW), (aH, 1))

									  # get position of original position

									  y = (y / ay)

									  x = (x / ax)

									  ix = np.floor(x).astype(np.int)

									  iy = np.floor(y).astype(np.int)

									  ix = np.minimum(ix, W-2)

									  iy = np.minimum(iy, H-2)

									  # get distance 

									  dx = x - ix

									  dy = y - iy

									  if C > 1:

									    dx = np.repeat(np.expand_dims(dx, axis=-1), C, axis=-1)

									    dy = np.repeat(np.expand_dims(dy, axis=-1), C, axis=-1)

									  # interpolation

									  out = (1-dx) * (1-dy) * img[iy, ix] + dx * (1 - dy) * img[iy, ix+1] + (1 - dx) * dy * img[iy+1, ix] + dx * dy * img[iy+1, ix+1]

									  out = np.clip(out, 0, 255)

									  out = out.astype(np.uint8)

									  return out

									# make image pyramid

									def make_pyramid(gray):

									  # first element

									  pyramid = [gray]

									  # each scale

									  for i in range(1, 6):

									    # define scale

									    a = 2. ** i

									    # down scale

									    p = bl_interpolate(gray, ax=1./a, ay=1. / a)

									    # add pyramid list

									    pyramid.append(p)

									  return pyramid

									# Read image

									img = cv2.imread("../bird.png").astype(np.float)

									gray = BGR2GRAY(img)

									# pyramid

									pyramid = make_pyramid(gray)

									for i in range(6):

									  cv2.imwrite("out_{}.jpg".format(2**i), pyramid[i].astype(np.uint8))

									  plt.subplot(2, 3, i+1)

									  plt.title('1/' + str((i+1)**2) )

									  plt.imshow(pyramid[i], cmap='gray')

									  plt.axis('off')

									  plt.xticks(color="None")

									  plt.yticks(color="None")

									plt.show()