For the purposes of approximate comparison between MetadataExtractor and .NET Framework alternatives, multiple scenarios are benchmarked. These focus on retrieving the "DateTimeOriginal" Exif value, as that is a common use case for this library.
From the directory containing this README file:
dotnet run -c Release
Results resemble (as of November 2016):
Host Process Environment Information:
BenchmarkDotNet.Core=v0.9.9.0
OS=Microsoft Windows NT 6.2.9200.0
Processor=Intel(R) Core(TM) i7-6700HQ CPU 2.60GHz, ProcessorCount=8
Frequency=2531248 ticks, Resolution=395.0620 ns, Timer=TSC
CLR=MS.NET 4.0.30319.42000, Arch=64-bit RELEASE [RyuJIT]
GC=Concurrent Workstation
JitModules=clrjit-v4.6.1586.0
Type=JpegBenchmark Mode=Throughput
Method | Median | StdDev | Scaled | Scaled-SD |
------------------------------------------ |------------ |----------- |------- |---------- |
JpegMetadataReaderOnlyExifReaderBenchmark | 30.1141 us | 0.7083 us | 1.00 | 0.00 |
JpegMetadataReaderBenchmark | 49.0014 us | 2.9799 us | 1.64 | 0.10 |
ImageMetadataReaderBenchmark | 48.3592 us | 1.2577 us | 1.60 | 0.05 |
SystemDrawingBenchmark | 322.4140 us | 7.2245 us | 10.62 | 0.33 |
WpfBitmapFrameCreateBenchmark | 678.8931 us | 13.3292 us | 22.36 | 0.65 |
WpfJpegBitmapDecoderBenchmark | 934.4390 us | 18.2268 us | 30.75 | 0.89 |
The most indicative measure of throughput comes from the Median column, where lower values are better.
Note that us indicates µs (microseconds, thousandths of milliseconds, or 10-6 seconds).
For these benchmarks, image data is loaded into a MemoryStream which is reused between test runs.
In general, IO will be the major limiting factor, and that is excluded by pre-loading data, however
it does minimise external influences on the results. MetadataExtractor is careful to avoid
unnecessary IO.
If you know you have JPEG data, and you only want Exif data, this is a fast option:
var directories = JpegMetadataReader.ReadMetadata(_stream, new[] { new ExifReader() });
var subIfdDirectory = directories.OfType<ExifSubIfdDirectory>().First();
var dateTime = subIfdDirectory.GetDateTime(ExifDirectoryBase.TagDateTimeOriginal);
Other kinds of metadata in the file will be ignored. Throws if the file does not actually contain JPEG data.
Retrieves all metadata from a JPEG file.
var directories = JpegMetadataReader.ReadMetadata(_stream);
var subIfdDirectory = directories.OfType<ExifSubIfdDirectory>().First();
var dateTime = subIfdDirectory.GetDateTime(ExifDirectoryBase.TagDateTimeOriginal);
Throws if the file does not contain JPEG data.
Determines the file type automatically, then proceeds to return all found metadata.
var directories = ImageMetadataReader.ReadMetadata(_stream);
var subIfdDirectory = directories.OfType<ExifSubIfdDirectory>().First();
var dateTime = subIfdDirectory.GetDateTime(ExifDirectoryBase.TagDateTimeOriginal);
This is the most general solution, and is recommended for most use cases. Throws if the file does not contain a supported file type.
Using System.Drawing is ~1,000% slower.
using (var myImage = Image.FromStream(_stream, useEmbeddedColorManagement: false, validateImageData: false))
{
const int PropertyTagExifDTOrig = ExifDirectoryBase.TagDateTimeOriginal;
var propItem = myImage.GetPropertyItem(PropertyTagExifDTOrig);
var dateTakenStr = Encoding.UTF8.GetString(propItem.Value);
var dateTime = DateTime.Parse(_dateTimeRegex.Replace(dateTakenStr, "-", count: 2));
}
Using WPF's BitmapFrame is ~2,200% slower.
var frame = BitmapFrame.Create(_stream, BitmapCreateOptions.DelayCreation, BitmapCacheOption.None);
var metadata = (BitmapMetadata)frame.Metadata;
var dateTakenStr = (string)metadata.GetQuery("/app1/ifd/exif/subifd:{uint=36867}");
var dateTime DateTime.Parse(_dateTimeRegex.Replace(dateTakenStr, "-", count: 2));
Using WPF's JpegBitmapDecoder is ~3,000% slower.
var decoder = new JpegBitmapDecoder(_stream, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.None);
var metadata = (BitmapMetadata)decoder.Frames[0].Metadata;
var dateTakenStr = (string)metadata.GetQuery("/app1/ifd/exif/subifd:{uint=36867}");
var dateTime DateTime.Parse(_dateTimeRegex.Replace(dateTakenStr, "-", count: 2));