关于ruby on rails：如何使用回形针将多页pdf缩略图化

How to thumbnail a multi-page pdf with paperclip

我想让回形针为上传的多页PDF文件的每一页创建2个缩略图。

我正在运行Paperclip 2.3.1.1，并在我的Asset模型中使用它：

1 2	has_attached_file :asset, :styles => { :medium =>"800x600>", :thumb =>"100x100>" }

因此，当我上传一个3页的pdf文件时，我希望这会在每页上创建2个大拇指(一个800x600像素，另一个较小的图像100x100)。相反，我创建了3个文件夹(拇指，中号，原始)-原始文件夹包含origianl pdf文件，而拇指和中号每个都包含一个pdf，而pdf的第一页都被像素化了。

我需要怎么做才能使回形针为pdf的每一页创建2个大拇指？理想情况下，我希望每页这样一张图片(创建6张图片)：

assets / 1 / medium / file-0.png

资产/1/medium/file-1.png

assets / 1 / medium / file-2.png

资产/ 1 /缩略图/文件-0.png

资产/ 1 /拇指/file-1.png

assets / 1 / thumb / file-2.png

有人知道该怎么做吗？我需要自定义处理器吗？如果是这样，处理器将是什么样？

谢谢。

这是我执行类似任务的方式。

文档模型：

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class Document < ActiveRecord::Base

has_many :pages, :dependent => :destroy

has_attached_file :asset

after_asset_post_process :make_pages

private

def make_pages
if valid?
Paperclip.run('convert',"-quality #{Page::QUALITY} -density #{Page::DENSITY} #{asset.queued_for_write[:original].path} #{asset.queued_for_write[:original].path}%d.png")
images = Dir.glob("#{asset.queued_for_write[:original].path}*.png").sort_by do |line|
line.match(/(\\d+)\\.png$/)[1].to_i
end

images.each do |page_image|
pages.build(:asset => File.open(page_image))
end
FileUtils.rm images
end
end
end

页面模型：

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class Page < ActiveRecord::Base

belongs_to :document

has_attached_file :asset

QUALITY = 100
DENSITY = '80x80'

end

相关讨论

我对此有半途而废的解决方案...但是它不是很优雅。我真的很想提出更好的建议，但我想还是应该分享。

我从定义一堆新样式开始，每页一个...直到我想要处理的许多页面。 (我知道这很愚蠢，但是我不知道如何访问回形针中的路径插值，以便每个页面都可以正确地保存/删除在存储中，除非每个图像都有独特的样式)

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{ ...
:page_0 => {:geometry=>'800[0]', :format=>:png, :processors=>[:multipage_thumbnail]},
:page_1 => {:geometry=>'800[1]', :format=>:png, :processors=>[:multipage_thumbnail]},
:page_2 => {:geometry=>'800[2]', :format=>:png, :processors=>[:multipage_thumbnail]},
:page_3 => {:geometry=>'800[3]', :format=>:png, :processors=>[:multipage_thumbnail]},
:page_4 => {:geometry=>'800[4]', :format=>:png, :processors=>[:multipage_thumbnail]},
:page_5 => {:geometry=>'800[5]', :format=>:png, :processors=>[:multipage_thumbnail]},
}

然后...我有一个自定义处理器，该处理器从Thumbnail处理器子类化，并带有一些额外的逻辑，用于在正确的页面#上运行convert命令。

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module Paperclip
# Handles thumbnailing images that are uploaded.
class MultipageThumbnail < Thumbnail

# Creates a Thumbnail object set to work on the +file+ given. It
# will attempt to transform the image into one defined by +target_geometry+
# which is a"WxH"-style string. +format+ will be inferred from the +file+
# unless specified. Thumbnail creation will raise no errors unless
# +whiny+ is true (which it is, by default. If +convert_options+ is
# set, the options will be appended to the convert command upon image conversion
def initialize file, options = {}, attachment = nil
@page = options[:geometry].match(/\\[(\\d+)\\]/)[1] rescue 0
@page ||= 0
options[:geometry] = options[:geometry].sub(/\\[\\d+\\]/, '')
super
end

# Performs the conversion of the +file+ into a thumbnail. Returns the Tempfile
# that contains the new image.
def make
return nil if @page >= page_count

src = @file
dst = Tempfile.new([@basename, @format].compact.join("."))
dst.binmode

begin
options = [
source_file_options,
"#{ File.expand_path(src.path) }[#{@page}]",
transformation_command,
convert_options,
"#{ File.expand_path(dst.path) }"
].flatten.compact

success = Paperclip.run("convert", *options)
rescue PaperclipCommandLineError => e
raise PaperclipError,"There was an error processing the thumbnail for #{@basename}" if @whiny
end

dst
end

def page_count
@page_count ||= begin
files = Paperclip.run("identify","#{@file.path}")
files.split(/\
/).size
rescue PaperclipCommandLineError
1
end
end

end
end