[Python][转载]比例缩放图片不变形

import cv2 import numpy as np

def resizeAndPad(img, size, padColor=0):     h, w = img.shape[:2]     sh, sw = size

    # interpolation method     if h > sh or w > sw:  # shrinking image         interp = cv2.INTER_AREA     else:  # stretching image         interp = cv2.INTER_CUBIC

    # aspect ratio of image     aspect = w / h  # if on Python 2, you might need to cast as a float: float(w)/h

    # compute scaling and pad sizing     if aspect > 1:  # horizontal image         new_w = sw         new_h = np.round(new_w / aspect).astype(int)         pad_vert = (sh - new_h) / 2         pad_top, pad_bot = np.floor(pad_vert).astype(int), np.ceil(pad_vert).astype(int)         pad_left, pad_right = 0, 0     elif aspect < 1:  # vertical image         new_h = sh         new_w = np.round(new_h * aspect).astype(int)         pad_horz = (sw - new_w) / 2         pad_left, pad_right = np.floor(pad_horz).astype(int), np.ceil(pad_horz).astype(int)         pad_top, pad_bot = 0, 0     else:  # square image         new_h, new_w = sh, sw         pad_left, pad_right, pad_top, pad_bot = 0, 0, 0, 0

    # set pad color     if len(img.shape) is 3 and not isinstance(padColor,                                               (list, tuple, np.ndarray)):  # color image but only one color provided         padColor = [padColor] * 3

    # scale and pad     scaled_img = cv2.resize(img, (new_w, new_h), interpolation=interp)     scaled_img = cv2.copyMakeBorder(scaled_img, pad_top, pad_bot, pad_left, pad_right, borderType=cv2.BORDER_CONSTANT,                                     value=padColor)

    return scaled_img

def resize_img_keep_ratio(img_name, target_size, color=(255, 255, 255)):     img = cv2.imread(img_name)     old_size = img.shape[0:2]     # ratio = min(float(target_size)/(old_size))     ratio = min(float(target_size[i]) / (old_size[i]) for i in range(len(old_size)))     new_size = tuple([int(i * ratio) for i in old_size])     img = cv2.resize(img, (new_size[1], new_size[0]))     pad_w = target_size[1] - new_size[1]     pad_h = target_size[0] - new_size[0]     top, bottom = pad_h // 2, pad_h - (pad_h // 2)     left, right = pad_w // 2, pad_w - (pad_w // 2)     img_new = cv2.copyMakeBorder(img, top, bottom, left, right, cv2.BORDER_CONSTANT, None, color)     return img_new

if __name__ == '__main__':     # 第一种方法     v_img = cv2.imread('v.jpg')  # vertical image     scaled_v_img = resizeAndPad(v_img, (200, 200), 127)

    # 第二种方法(推荐)     img = 'D:/test1.jpg'     target_size = [500, 100]     new_image = resize_img_keep_ratio(img, target_size)     cv2.imshow('result', new_image)     cv2.waitKey(0)