如何在Rails中使用mini_magick解码base64图像文件？ [英] How to decode base64 image file with mini_magick in Rails?

问题描述

在我们的Rails 4应用程序中，图像以base64字符串上传到服务器：

In our Rails 4 app, the image is uploaded to server in a base64 string:

uploaded_io = "data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2....."

我们想要检索内容类型，大小等，并将文件保存为文件系统上的图像文件。我们的应用程序中有一个 gem'mini_magick'。有没有办法用 mini_magick 处理base64图像字符串？

We would like to to retrieve the content type, size and so on and save the file as image file on file system. There is a gem 'mini_magick' in our app. Is there a way to process base64 image string with mini_magick?

推荐答案

是的，有办法做到这一点。

Yes, there is a way to do that.

从输入字符串中剥离元数据data：image / jpeg; base64，然后用<解码 Base64.decode64 方法。你会得到二进制blob。将blob提供给 MiniMagick :: Image.read 。 ImageMagick非常聪明，可以为您猜测所有元数据。然后像往常一样使用 mini_magick 方法处理图像。

Strip metadata "data:image/jpeg;base64," from your input string and then decode it with Base64.decode64 method. You'll get binary blob. Feed that blob to MiniMagick::Image.read. ImageMagick is smart enough to guess all metadata for you. Then process the image with mini_magick methods as usual.

require 'base64'

uploaded_io = "data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2....."
metadata = "data:image/jpeg;base64,"
base64_string = uploaded_io[metadata.size..-1]
blob = Base64.decode64(base64_string)
image = MiniMagick::Image.read(blob)
image.write 'image.jpeg'

# Retrieve attributes
image.type        # "JPEG"
image.mime_type   # "image/jpeg"
image.size        # 458763
image.width       # 640
image.height      # 480
image.dimensions  # [640, 480]

# Save in other format
image.format 'png'
image.write 'image.png'

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