Python使用OpenCV转换图像大小

pip install opencv-python

import cv2  
  
def resize_image(input_image_path, output_image_path, width=None, height=None, inter=cv2.INTER_AREA):  
    """  
    调整图像大小  
  
    :param input_image_path: 输入图像的路径  
    :param output_image_path: 输出图像的路径  
    :param width: 目标宽度，如果为None，则不改变宽度  
    :param height: 目标高度，如果为None，则不改变高度  
    :param inter: 插值方法，默认为cv2.INTER_AREA（适用于缩小图像）  
    :return: None  
    """  
    # 读取图像  
    image = cv2.imread(input_image_path)  
    if image is None:  
        print(f"Error: Unable to load image at {input_image_path}")  
        return  
  
    # 检查是否指定了宽度和高度  
    if width is None and height is None:  
        print("Error: Both width and height cannot be None.")  
        return  
  
    # 如果只指定了宽度或高度，则计算另一个维度以保持图像的宽高比  
    if width is None:  
        width = int(image.shape[1] * (height / float(image.shape[0])))  
    elif height is None:  
        height = int(image.shape[0] * (width / float(image.shape[1])))  
  
    # 调整图像大小  
    resized_image = cv2.resize(image, (width, height), interpolation=inter)  
  
    # 显示图像（可选）  
    cv2.imshow('Resized Image', resized_image)  
    cv2.waitKey(0)  # 等待按键  
    cv2.destroyAllWindows()  
  
    # 保存图像  
    cv2.imwrite(output_image_path, resized_image)  
  
# 使用示例  
input_image = 'path_to_your_image.jpg'  # 替换为你的图像路径  
output_image = 'resized_image.jpg'  
resize_image(input_image, output_image, width=640, height=480)

import cv2  
  
def resize_image_keep_aspect_ratio(input_image_path, output_image_path, max_width=None, max_height=None, inter=cv2.INTER_AREA):  
    """  
    调整图像大小，同时保持宽高比  
  
    :param input_image_path: 输入图像的路径  
    :param output_image_path: 输出图像的路径  
    :param max_width: 最大宽度，如果为None，则不限制宽度  
    :param max_height: 最大高度，如果为None，则不限制高度  
    :param inter: 插值方法，默认为cv2.INTER_AREA（适用于缩小图像）  
    :return: None  
    """  
    # 读取图像  
    image = cv2.imread(input_image_path)  
    if image is None:  
        print(f"Error: Unable to load image at {input_image_path}")  
        return  
  
    # 获取原始图像的宽高  
    height, width = image.shape[:2]  
  
    # 计算新的尺寸  
    if max_width is None and max_height is None:  
        print("Error: Both max_width and max_height cannot be None.")  
        return  
    elif max_width is None:  
        max_width = int(width * (max_height / float(height)))  
    elif max_height is None:  
        max_height = int(height * (max_width / float(width)))  
    else:  
        # 确保宽度和高度不会超过指定的最大值，同时保持宽高比  
        ratio = min(max_width / width, max_height / height)  
        max_width = int(width * ratio)  
        max_height = int(height * ratio)  
  
    # 调整图像大小  
    resized_image = cv2.resize(image, (max_width, max_height), interpolation=inter)  
  
    # 保存图像  
    cv2.imwrite(output_image_path, resized_image)  
  
    # 可选：显示图像（注意，在生产环境中通常不会这样做）  
    # cv2.imshow('Resized Image with Aspect Ratio', resized_image)  
    # cv2.waitKey(0)  
    # cv2.destroyAllWindows()  
  
# 使用示例  
input_image = 'your_image.jpg'  # 替换为你的图像文件路径  
output_image = 'resized_image_with_aspect_ratio.jpg'  
resize_image_keep_aspect_ratio(input_image, output_image, max_width=800)  # 只指定最大宽度  
# 或者  
# resize_image_keep_aspect_ratio(input_image, output_image, max_height=600)  # 只指定最大高度