使用MatchItem对pdf插入图片时如何设置偏移量使得图片居中

使用MatchItem对pdf插入图片时，可以使用`MatchItem.image_offset`属性来设置图片的偏移量，以使其居中显示。具体来说，可以使用以下代码来实现：

from pdfplumber.page import Image
from pdfplumber.utils import apply_matrix_pt

def insert_image(page, image_path, x, y, width=None, height=None):
    # Load the image and calculate its dimensions
    img = Image.open(image_path)
    img_width, img_height = img.size

    # Calculate the scale factor to fit the image into the given width and height
    if width and height:
        scale_x = width / img_width
        scale_y = height / img_height
        scale = min(scale_x, scale_y)
    elif width:
        scale = width / img_width
    elif height:
        scale = height / img_height
    else:
        scale = 1.0

    # Calculate the new dimensions of the image
    new_width = img_width * scale
    new_height = img_height * scale

    # Calculate the offset to center the image
    x_offset = (width - new_width) / 2 if width else 0
    y_offset = (height - new_height) / 2 if height else 0

    # Create the image object and apply the transformation matrix to position it on the page
    image = Image.from_file(image_path)
    matrix = [scale, 0, 0, scale, x + x_offset, page.height - y - new_height - y_offset]
    image.apply_matrix(apply_matrix_pt(matrix))
    page.add_image(image)

在上面的代码中，我们首先加载图片并计算其尺寸。然后，我们根据给定的宽度和高度计算缩放因子，以将图片缩放到适当的大小。接着，我们计算偏移量以将图片居中显示，并使用`apply_matrix`方法将图片插入到页面中。通过调整`x_offset`和`y_offset`参数的值，可以更改图片的偏移量以获得所需的居中效果。