Makes it optional to load JPEG thumbnails from Tiff files

[rcpalacio]

Hi

Some use cases of EXIFR don't actually require loading JPEG thumbnails from TIFF files.

As files are getting larger and larger recently, so are the thumbnails. This means we can save quite a lot of I/O operations in scenarios where these thumbnails are not necessary and throughput is critical.

[remvee]

Hi @rcpalacio, Thank you for your contribution! I'd prefer a keyword argument for this and I'm open to breaking compatibility with ruby-1.9 for this. So what about adding:

diff --git a/lib/exifr/tiff.rb b/lib/exifr/tiff.rb
index a50765a..133efdd 100644
--- a/lib/exifr/tiff.rb
+++ b/lib/exifr/tiff.rb
@@ -375,7 +375,7 @@ module EXIFR
     TAGS = [TAG_MAPPING.keys, TAG_MAPPING.values.map{|v|v.values}].flatten.uniq - IFD_TAGS
 
     # +file+ is a filename or an +IO+ object.  Hint: use +StringIO+ when working with slurped data like blobs.
-    def initialize(file, load_thumbnails = true)
+    def initialize(file, load_thumbnails: true)
       Data.open(file) do |data|
         @ifds = [IFD.new(data)]
         while ifd = @ifds.last.next
diff --git a/tests/tiff_test.rb b/tests/tiff_test.rb
index 76be654..ddf845a 100755
--- a/tests/tiff_test.rb
+++ b/tests/tiff_test.rb
@@ -190,7 +190,7 @@ class TIFFTest < TestCase
 
   def test_skippable_jpeg_thumbnails
     all_test_tiffs.each do |fname|
-      t = TIFF.new(fname, false)
+      t = TIFF.new(fname, load_thumbnails: false)
       assert t.jpeg_thumbnails.empty?
     end
   end

Also, let's not forget about JPEG by adding:

diff --git a/lib/exifr/jpeg.rb b/lib/exifr/jpeg.rb
index aa7d3e9..19d16ec 100644
--- a/lib/exifr/jpeg.rb
+++ b/lib/exifr/jpeg.rb
@@ -29,11 +29,11 @@ module EXIFR
     attr_reader :app1s
 
     # +file+ is a filename or an IO object.  Hint: use StringIO when working with slurped data like blobs.
-    def initialize(file)
+    def initialize(file, load_thumbnails: true)
       if file.kind_of? String
-        File.open(file, 'rb') { |io| examine(io) }
+        File.open(file, 'rb') { |io| examine(io, load_thumbnails: true) }
       else
-        examine(file.dup)
+        examine(file.dup, load_thumbnails: true)
       end
     end
 
@@ -121,7 +121,7 @@ module EXIFR
 
       if app1 = @app1s.find { |d| d[0..5] == "Exif\0\0" }
         @exif_data = app1[6..-1]
-        @exif = TIFF.new(StringIO.new(@exif_data))
+        @exif = TIFF.new(StringIO.new(@exif_data), load_thumbnails: load_thumbnails)
       end
     end
   end

WDYT?

[rcpalacio]

Thanks for looking into it so quickly!
I definitely agree, it reads better. I'll incorporate those the changes.

[rcpalacio]

I wonder if the failure on ruby 2.2 is related to this issue: ruby/setup-ruby#496

About 1.9, I'll drop it from .github/workflows/test.yml.

[remvee]

Thanks!