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[#]: collector: (lujun9972)
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[#]: translator: (geekpi)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Resize images using Python)
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[#]: via: (https://opensource.com/life/15/2/resize-images-python)
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[#]: author: (Dayo Ntwari https://opensource.com/users/dayontwari)
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Resize images using Python
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======
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A quick explanation of how to resize images in Python while keeping the
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same aspect ratio.
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![Python in a tree][1]
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I love [Python][2], and I've been learning it for a while now. Some time ago, I wrote a Python script where I needed to resize a bunch of images while at the same time keeping the aspect ratio (the proportions) intact. So I looked around and found [Pillow][3], a Python imaging library and "friendly fork" of an old library just called PIL.
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To install Pillow, use the `pip` module of Python:
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```
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`$ python3 -m pip install Pillow`
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```
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### Scaling by width
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Here's a basic script to resize an image using the Pillow module:
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```
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from PIL import Image
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basewidth = 300
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img = Image.open('fullsized_image.jpg')
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wpercent = (basewidth / float(img.size[0]))
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hsize = int((float(img.size[1]) * float(wpercent)))
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img = img.resize((basewidth, hsize), Image.ANTIALIAS)
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img.save('resized_image.jpg')
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```
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These few lines of Python code resize an image (**fullsized_image.jpg**) using Pillow to a width of 300 pixels, which is set in the variable **basewidth** and a height proportional to the new width. The proportional height is calculated by determining what percentage 300 pixels is of the original width (**img.size[0]**) and then multiplying the original height (**img.size[1]**) by that percentage. The resulting height value is saved in the variable **hsize.**
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You can change **basewidth** to any other number if you need a different width for your images. Also, notice I saved the resized image under a different name, **resized_image.jpg**, because I wanted to preserve the full-size image (**fullsized_image.jpg**) as well. You don't have to do this, of course. You can use the same filename to overwrite the full-size image with the resized image, if that is what you want.
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### Scaling by height
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If the height is fixed and the width proportionally variable, it's pretty much the same thing, you just need to switch things around a bit:
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```
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from PIL import Image
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baseheight = 560
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img = Image.open('fullsized_image.jpg')
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hpercent = (baseheight / float(img.size[1]))
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wsize = int((float(img.size[0]) * float(hpercent)))
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img = img.resize((wsize, baseheight), Image.ANTIALIAS)
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img.save('resized_image.jpg')
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```
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Notice **basewidth** is now **baseheight**, since height is fixed. In the third line, we are calculating the height percentage, so we need **img.size[1]** instead of **img.size[0]**. The size attribute is a tuple containing width and height in pixels; **size[0]** refers to the first tuple element, which is the width, and **size[1]** is the second element, which is height. Line 4 also has this switch between **size[0]** for width and **size[1]** for height.
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_Originally published on Dayo Ntwari's [blog][4] and republished under Creative Commons with permission._
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_This article was updated in January 2021 by the editor._
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--------------------------------------------------------------------------------
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via: https://opensource.com/life/15/2/resize-images-python
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作者：[Dayo Ntwari][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://opensource.com/users/dayontwari
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/life-python.jpg?itok=F2PYP2wT (Python in a tree)
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[2]: http://python.org/ (Python Programming Language – Official Website)
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[3]: https://pypi.org/project/Pillow/ (Python Imaging Library)
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[4]: https://dayontwari.wordpress.com/2015/01/06/how-to-resize-images-with-python/
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82
translated/tech/20210101 Resize images using Python.md
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82
translated/tech/20210101 Resize images using Python.md
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@ -0,0 +1,82 @@
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[#]: collector: (lujun9972)
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[#]: translator: (geekpi)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Resize images using Python)
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[#]: via: (https://opensource.com/life/15/2/resize-images-python)
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[#]: author: (Dayo Ntwari https://opensource.com/users/dayontwari)
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使用 Python 调整图像大小
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======
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快速解释如何在 Python 中调整图像大小，同时保持相同的长宽比。
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![Python in a tree][1]
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我喜欢 [Python][2]，而且我已经学了一段时间了。前段时间，我写了一个 Python 脚本，在这个脚本中，我需要调整一堆图片的大小，同时保持长宽比（比例）不变。于是我四处寻找，发现了 [Pillow][3]，这是一个 Python 图像库，也是一个叫做 PIL 的旧库的”友好分叉“。
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要安装 Pillow，请使用 Python 的 `pip` 模块：
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```
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`$ python3 -m pip install Pillow`
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```
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### 按宽度缩放
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这是一个使用 Pillow 模块来调整图片大小的基本脚本：
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```
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from PIL import Image
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basewidth = 300
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img = Image.open('fullsized_image.jpg')
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wpercent = (basewidth / float(img.size[0]))
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hsize = int((float(img.size[1]) * float(wpercent)))
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img = img.resize((basewidth, hsize), Image.ANTIALIAS)
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img.save('resized_image.jpg')
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```
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这几行 Python 代码使用 Pillow 将一张图片 （**fullsized_image.jpg**） 调整为 300 像素的宽度，宽度在变量 **basewidth** 中设置，高度则与新的宽度成比例。比例高度的计算方法是：确定 300 像素占原宽度 （**img.size[0]**） 的百分比，然后将原高度 （**img.size[1]**） 乘以该百分比。所得的高度值保存在变量 **hsize** 中。
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如果你需要不同的图片宽度，你可以将 **basewidth** 改为任何其他数字。另外，请注意，因为我想保留全尺寸的图片 （**fullsized_image.jpg**），因此我将调整后的图片以一个不同的名称 **resized_image.jpg** 保存。当然，你不必这么做。如果你想要这么做，你可以使用相同的文件名将调整后的图片覆盖全尺寸的图片。
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### 按高度缩放
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如果高度是固定的，而宽度是按比例变化的，那也基本差不多，你只需要把东西换一下：
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```
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from PIL import Image
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baseheight = 560
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img = Image.open('fullsized_image.jpg')
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hpercent = (baseheight / float(img.size[1]))
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wsize = int((float(img.size[0]) * float(hpercent)))
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img = img.resize((wsize, baseheight), Image.ANTIALIAS)
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img.save('resized_image.jpg')
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```
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注意 **basewidth** 现在是 **baseheight**，因为高度是固定的。在第三行中，我们在计算高度百分比，所以我们需要 **img.size[1]** 而不是 **img.size[0]**。size 属性是一个元组，包含宽度和高度，单位是像素，**size[0]** 指的是第一个元组元素，也就是宽度，**size[1]** 是第二个元素，也就是高度。第 4 行也有这样的切换，**size[0]** 代表宽度，**size[1]** 代表高度。
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_最初发表在 Dayo Ntwari 的[博客][4]上，经允许后在 Creative Commons 许可下转载。_
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_本文由编辑于 2021 年 1 月更新。_
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--------------------------------------------------------------------------------
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via: https://opensource.com/life/15/2/resize-images-python
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作者：[Dayo Ntwari][a]
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选题：[lujun9972][b]
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译者：[geekpi](https://github.com/geekpi)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://opensource.com/users/dayontwari
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/life-python.jpg?itok=F2PYP2wT (Python in a tree)
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[2]: http://python.org/ (Python Programming Language – Official Website)
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[3]: https://pypi.org/project/Pillow/ (Python Imaging Library)
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[4]: https://dayontwari.wordpress.com/2015/01/06/how-to-resize-images-with-python/
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