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`GoogleCloudVision::OcrPdfService.new('path/to/document.pdf').perform` yields each page's text.
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require 'google/cloud/vision' | |
def log(s); puts s; end | |
module GoogleCloudVision | |
class OcrPdfService | |
attr_accessor :pdf_filename | |
def initialize(pdf_filename) | |
fail "GOOGLE_CLOUD_KEYFILE env variable required" unless ENV['GOOGLE_CLOUD_KEYFILE'] | |
fail "Input must be PDF" unless pdf_filename&.split('.')&.last&.downcase == 'pdf' | |
self.pdf_filename = pdf_filename | |
log :page_count, self.page_count | |
end | |
def perform | |
[].tap do |pages| | |
self.page_count.times do |i| | |
tempfile = Tempfile.new(%w(image .jpg)) | |
begin | |
log :writing_image, tempfile.path | |
write_pdf_page_to_jpg(i, tempfile.path) | |
log :compressing_image | |
log :loading_image | |
image = vision.image(tempfile.path) | |
image.context.languages = ['en-US'] | |
log :annotating_image | |
annotation = vision.annotate(image, document: true) | |
ensure | |
tempfile.close | |
tempfile.unlink | |
end | |
log :extracting_text | |
text = annotation.text.to_s | |
log self.pdf_filename, i, text | |
yield [text, i] if block_given? | |
pages << text | |
end | |
end | |
end | |
protected | |
def page_count | |
@page_count ||= `gs -q -dNODISPLAY -c "(#{self.pdf_filename}) (r) file runpdfbegin pdfpagecount = quit";`.to_i | |
end | |
private | |
def vision | |
@vision ||= Google::Cloud::Vision.new(project: ENV['GOOGLE_CLOUD_PROJECT_ID']) | |
end | |
def write_pdf_page_to_jpg(page_num, file_path) | |
command = <<-EOS.squish | |
gs -sDEVICE=jpeg | |
-dBATCH | |
-dNOPAUSE | |
-r225 | |
-sOutputFile=#{file_path} | |
-dFirstPage=#{page_num+1} | |
-dLastPage=#{page_num+1} | |
-dJPEGQ=40 | |
#{self.pdf_filename} | |
EOS | |
`#{ command }` | |
log :file, file_path, :page_num, page_num, :bytes, File.size(file_path) | |
end | |
end | |
end | |
end |
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