如何使用 PIL 调整图像大小并保持其纵横比? [英] How do I resize an image using PIL and maintain its aspect ratio?

问题描述

是否有明显的方法可以做到这一点，但我缺少这种方法?我只是想制作缩略图.

Is there an obvious way to do this that I'm missing? I'm just trying to make thumbnails.

推荐答案

定义最大尺寸.然后，通过取min(maxwidth/width, maxheight/height)来计算调整大小比例.

Define a maximum size. Then, compute a resize ratio by taking min(maxwidth/width, maxheight/height).

合适的尺寸是oldsize*ratio.

当然还有一个库方法可以做到这一点:方法Image.thumbnail.
下面是 PIL 文档 中的(经过编辑的)示例.

There is of course also a library method to do this: the method Image.thumbnail.
Below is an (edited) example from the PIL documentation.

import os, sys
import Image

size = 128, 128

for infile in sys.argv[1:]:
    outfile = os.path.splitext(infile)[0] + ".thumbnail"
    if infile != outfile:
        try:
            im = Image.open(infile)
            im.thumbnail(size, Image.ANTIALIAS)
            im.save(outfile, "JPEG")
        except IOError:
            print "cannot create thumbnail for '%s'" % infile

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