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Image resize in dotNet: from JPG to JPG on Windows OS ​

1-1-2024 - updated 16-1-2024

Introduction ​

The guys of Team Xerbutri asked me to improve the imagery on their new website.

That is a bit of a broad question, so where to start?

What image formats are in play these days? What sizes are used? What is the most expensive process?

Image resizing is the most expensive process.

Resizing and adding watermarks takes a lot of time, and was done in old applications, batch processing the pictures in Jasc PSP and saving the images multiple times as jpg, degrading the picture quality. In the wake of the modernization and automation of this process I will write some blogposts.

My Question:
Can I resize images with a dotNet package? If so, what is the best package to use?

Boundary conditions ​

In this test I used the 12 pictures by Bertrand Le Roy.
I am running almost exactly the same benchmark, updated slightly to 2023.

In this test:

  • uses 12 pictures of 500kB size each, ~1280 x ~900 px
  • resizes to thumbnail size (150px)
  • benchmarking of load, resize and save operations
  • using .NET 8
  • using Windows 11 only
  • saves the original jpeg as 75% quality jpeg format

Considerations ​

I wanted to include at least the packages from the 2017 test by Bertrand Le Roy:

  • System.Drawing, the newest version named System.Drawing.Common
  • ImageSharp
  • Magick.NET
  • SkiaSharp
  • FreeImage

I did some research, and considered the following packages.

  • ImageFlow, which I added to the test
  • Microsoft.Maui.Graphics. I tried, but there is no support for Windows 11 at this moment, leaving you the choice to wrap around System.Drawing (already in this test) or SkiaSharp (also in this test)
  • Image resizer, which is for .NET framework. For .NET 8 it recommends to use ImageFlow.
  • ImageProcessor which is for .NET framework and is dead. It was a wrapper around System.Drawing (in this test). It recommends ImageSharp for .NET (Core).

About the packages ​

The implementation code is in my GitHub imageresize.benchmark repository.

System.Drawing.Common ​

This package provides access to GDI+ graphics (Windows) functionality.
Non-Windows platforms are not supported since .NET 7, even with the runtime configuration switch. See System Drawing on Windows for more information. It is very popular and for its many versions there are lots of examples. The implementation is a bit more messy compared to ImageSharp or Magick.NET.

ImageSharp ​

ImageSharp is a fully featured, fully managed, cross-platform, 2D graphics library.
It is quite easy to implement. I had to fiddle a little bit, but it was not that difficult.

Magick.NET ​

Magick.NET is a wrapper around the ImageMagick library. It has extensive file support.
Code implementation is very clean and very easy, but I had to figure out which nuget package(s) to use.

MagicScaler ​

MagicScaler is a high-performance image processing pipeline for .NET, focused on making complex imaging tasks simple. They claim their speed and efficiency are unmatched by anything else on the .NET platform.
Let's see about that later.

This package currently has full functionality only on Windows.

The implementation took a bit of fiddling around since I wanted to control the output size of the picture.

MagicScaler is still on version 0, this might indicate there is no production version available yet.

SkiaSharp ​

SkiaSharp is a wrapper around Google's Skia Graphics library. Skia is an open source 2D graphics library which provides common APIs that work across a variety of hardware and software platforms. It serves as the graphics engine for Google Chrome and ChromeOS, Android, Flutter, and many other products.

Making this library work on Windows 11 took me no effort at all, and for me it worked out of the box. The implemented code looks a bit strange to me, and I relied heavily on some examples I found online. However, microsoft have pages about skia in their documentation, so I guess it has their full support, which is nice.

Free Image ​

I only included this package because it was in the previous test. It is a .NET wrapper around the FreeImage library. This library is no longer maintained, and it seems FreeImage.NET is also no longer maintained.

Implementation is the shortest with just 4 lines of code. It is however a bit ugly in style and hard to understand at first sight because of the descriptive nature. For example: JPEG_QUALITYGOOD means 75%. For me, having worked with images for all my life, 75% is very clear to me. I will never say this picture-compression will be good or have any quality. It makes me feel bad.

ImageFlow ​

Imageflow.NET is a .NET API for Imageflow, an image optimization and processing library for web servers. Imageflow focuses on security, quality, and performance - in that order. Imageflow.NET is a .NET Standard 2.0 library, and as such is compatible with .NET 4.6.2+, .NET Core 2.0+, and .NET 5/6/7/8.

Imageflow.NET is tri-licensed under a commercial license, the AGPLv3, and the Apache 2 license, which would drive any manager mad.

The implementation for me feels crazy. If you are familiar to ImageResizer, you may disagree with me but... ARGH!! Cooties!! I copied an example piece of code. And I hate it. It has all the expensive stuff in it which I always try to avoid. It is the only async one. It has the ResizerCommands from the old ImageResizer package. For me it feels awkward. I think I could easily improve this piece of code to make me feel less itchy, but I do not want to touch it. ImageFlow is still on version 0, this might indicate there is no production version available yet.

Packages summarized ​

A summary of the packages used in this table:

PackageLicensePublishedVersionDownloads
System.DrawingMIT11-20236.0.01124.1 M
ImageSharpSix Labors split12-20233.1.177.6 M
Magick.NetApache 2.012-202313.5.015.0 M
MagicScalerMIT10-20230.14.00.7 M
SkiaSharpMIT9-20232.88.669.1 M
FreeImageFree Image6-20194.3.80.07 M
ImageFlowtri or bi-license AGPL9-20230.10.20.3 M

I added the license information for your managers if you want to use this software in company code. I find managers to often dislike (or forbid) copyleft-type licenses.

Most of the packages are in full support or development, except Free Image which has not been updated for a while. System.Drawing and Skiasharp are Microsoft backed packages. This could be an advantage in terms of support.

MagicScaler and ImageFlow are still on the zero version, which might indicate there is no official production version yet.

System.Drawing.Common is the most popular with 1124 million downloads!!
ImageSharp comes second, closely followed by SkiaSharp. A far fourth is Magick.NET.
MagicScaler and ImageFlow are promising packages, but they are not that popular.

Results in numbers ​

The results of this test in numbers: the time elapsed to produce the pictures, the memory used and the resulting filesize.

Time elapsed ​

The time elapsed is just an indication, as run on my laptop. So please just focus on the ratio. The picture below shows the default output by Benchmarking.NET. It shows the time per operation.

Time per operation

This is the speed per operation as output from benchmark dotnet. ImageFlow is off the chart, this is not a mistake. It seems fast as lightning. ImageFlow spins up a huge amount of operations, so one operation is very fast. However, it does take a lot of operations and overhead to get this done.

The total time elapsed gives a better comparison:

Time total

Now this looks very different!
ImageFlow is now slowest. Spinning up >500 operations has the downside of having a lot of overhead on my system, in this test. Another test may have another outcome!
Magick.NET is now the fastest package overall, while being the slowest package per operation.

Conclusion ​

In this test I am not interested in per operation statistics, I want to know how long it takes to resize all of my images.

For this test, loading, resizing and saving with 12 images of 0,5 MB size:
Magick.NET is clearly fastest.
ImageFlow is the slowest.
All others show decent performance.

I created an other test for the Xerbutri scenario, but here I wanted to be able to compare with the results by Bertrand Le Roy.

A quick flashback to the claims: ​

MagicScaler: "speed and efficiency are unmatched by anything else on the .NET platform"
Their speed is actually exactly in the middle in this test. The Xerbutri test showed similar results in a heavier test. Speed is not their unique selling point.

SkiaSharp was made for speed, and it is second fastest in this test. It maintains this position in the second heavier test.

ImageFlow mentions fast in its description, but in this test it is not.

Memory usage ​

The next picture shows allocated memory usage. For your machine this does not matter, as generally speaking the amount of memory on your own machine is sufficient. If you have functions or other an app in the cloud where you pay for memory (or simply crash on memory overload), this is very relevant.

Memory used

The packages System.Drawing, Magick.NET, SkiaSharp and FreeImage have low memory usage and are clear winners on this area. Having many operations takes its toll on the memory usage of ImageFlow.

ImageSharp has by far the highest memory usage and is a bit absurd, taking twice the amount of a picture-size on disk. I am interested in the performance of these package with larger pictures.

Conclusion ​

System.Drawing and Magick.NET are clear winners.
Skiasharp, MagicScaler, and FreeImage show decent performance.
ImageFlow is a bit on the high side, but it is paying for the overhead of its many operations in this test. ImageSharp has crazy high memory usage in this test, and I would like to see its performance in the upcoming test.

File size ​

File size

SkiaSharp and ImageFlow have lowest file sizes. I am not going to touch this, because if you care about file size, you do not use JPEG format in 2024. I think all packages are doing a decent job, Skia and ImageFlow are the best.

Quality ​

Quality of the pictures is subjective.

I want to show you two cases: contrast and bokeh.

This is the original high contrast picture. Original1

And here are the produced thumbnails.

Package
System.DrawingDSCN0533 System.Drawing
ImageSharpDSCN0533-ImageSharp
Magick.NetDSCN0533-MagickNET
MagicScalerDSCN0533-MagicScaler
SkiaSharpDSCN0533-SkiaSharp
FreeImageDSCN0533-FreeImage
ImageFlowDSCN0533-Imageflow

All of the thumbnails are troublesome the least, they do not look good. All of the algorithms struggle with the high contrast, and leave pixelated areas around the lamp. Overall I like System.Drawing and MagicScaler the best.

Bokeh plant ​

The first Bokeh-example with a red flowery plant.

Original1

Package
System.DrawingIMG_2301 System.Drawing
ImageSharpIMG_2301-ImageSharp
Magick.NetIMG_2301-MagickNET
MagicScalerIMG_2301-MagicScaler
SkiaSharpIMG_2301-SkiaSharp
FreeImageIMG_2301-FreeImage
ImageFlowIMG_2301-Imageflow

Again, System.Drawing and MagicScaler are fine. ImageSharp is nice as well. The colors of Magick.NET, SkiaSharp and FreeImage look greyish.

Bokeh snake ​

The second example with the snake, which also shows the greens.

Original1

Package
System.DrawingIMG_2325 System.Drawing
ImageSharpIMG_2325-ImageSharp
Magick.NetIMG_2325-MagickNET
MagicScalerIMG_2325-MagicScaler
SkiaSharpIMG_2325-SkiaSharp
FreeImageIMG_2325-FreeImage
ImageFlowIMG_2325-Imageflow

Again here, the colors of Magick.NET, Skia and FreeImage are clearly off compared to the original. The Bokeh effect is preserved by System.Drawing, ImageSharp, Magick.Net and MagicScaler

Overall picture comparison ​

Compare all of the thumbnails:

PackageSystem.DrawingImageSharpMagick.NetMagicScalerSkiaSharpFreeImageImageFlow
1DSCN0533 System.DrawingDSCN0533-ImageSharpDSCN0533-MagickNETDSCN0533-MagicScalerDSCN0533-SkiaSharpDSCN0533-FreeImageDSCN0533-Imageflow
2IMG_2301 System.DrawingIMG_2301-ImageSharpIMG_2301-MagickNETIMG_2301-MagicScalerIMG_2301-SkiaSharpIMG_2301-FreeImageIMG_2301-Imageflow
3IMG_2317 System.DrawingIMG_2317-ImageSharpIMG_2317-MagickNETIMG_2317-MagicScalerIMG_2317-SkiaSharpIMG_2317-FreeImageIMG_2317-Imageflow
4IMG_2325 System.DrawingIMG_2325-ImageSharpIMG_2325-MagickNETIMG_2325-MagicScalerIMG_2325-SkiaSharpIMG_2325-FreeImageIMG_2325-Imageflow
5IMG_2351 System.DrawingIMG_2351-ImageSharpIMG_2351-MagickNETIMG_2351-MagicScalerIMG_2351-SkiaSharpIMG_2351-FreeImageIMG_2351-Imageflow
6IMG_2443 System.DrawingIMG_2443-ImageSharpIMG_2443-MagickNETIMG_2443-MagicScalerIMG_2443-SkiaSharpIMG_2443-FreeImageIMG_2443-Imageflow
7IMG_2445 System.DrawingIMG_2445-ImageSharpIMG_2445-MagickNETIMG_2445-MagicScalerIMG_2445-SkiaSharpIMG_2445-FreeImageIMG_2445-Imageflow
8IMG_2446 System.DrawingIMG_2446-ImageSharpIMG_2446-MagickNETIMG_2446-MagicScalerIMG_2446-SkiaSharpIMG_2446-FreeImageIMG_2446-Imageflow
9IMG_2525 System.DrawingIMG_2525-ImageSharpIMG_2525-MagickNETIMG_2525-MagicScalerIMG_2525-SkiaSharpIMG_2525-FreeImageIMG_2525-Imageflow
10IMG_2565 System.DrawingIMG_2565-ImageSharpIMG_2565-MagickNETIMG_2565-MagicScalerIMG_2565-SkiaSharpIMG_2565-FreeImageIMG_2565-Imageflow
11IMG_2734 System.DrawingIMG_2734-ImageSharpIMG_2734-MagickNETIMG_2734-MagicScalerIMG_2734-SkiaSharpIMG_2734-FreeImageIMG_2734-Imageflow
12sample System.Drawingsample-ImageSharpsample-MagickNETsample-MagicScalersample-SkiaSharpsample-FreeImagesample-Imageflow

Conclusion ​

Best picture quality in this test:

  • System.Drawing
  • ImageSharp
  • MagicScaler

Good Quality:

  • ImageFlow, the pictures are a bit blurry

Mediocre Quality

  • SkiaSharp is blurry and colors are off
  • FreeImage colors are off
  • Magick.NET colors are off

Please do mind that the way the test is performed influences the outcome of the test. For each packag the default settings are used, with the least amount of fuzz. I believe it is possible for all of these packages to create pictures of comparable quality, but it will take you more time to tune the settings.

Conclusion ​

What is the best package?
It depends.

What does best mean for you?

Quality matters to me most. These are my favorites:

  • System.Drawing
  • ImageSharp
  • MagicScaler

ImageSharp has a good picture quality out of the box, it is a managed code library, no trouble with platform support, and easy to play around with. The downsides are memory usage and the license.

MagicScaler has a good picture quality out of the box, it is quite fast, does not use excessive memory. But it currently only has full functionality on Windows. Also it is on version 0 which might indicate it is not ready for production. I think it is a potential winner.

System.Drawing is overall the best package, with low memory usage, good picture quality and it is quite fast. Downside is the windows only support.

I am really interested in developments around Skia, since there is lots of talk around it on Maui, and Microsoft seems to push it. So I expect it to improve in the near future.

Remarks ​

Remarks on the results:

First of all: Who saves an image as jpeg in 2024?
I mean: If you like images, who is going to turn a jpeg into a jpeg, because you are destroying the image.
You would more likely save it as a PNG, or as a Webp image file. More about that in an upcoming blog!

You could set required output, like file-size or quality and achieve different results. For example, there are complaints about the image quality by the SkiaSharp package, but on the github issues you will find tricks to improve image quality. The scope of this test was to have comparable input, and compare the output of the packages.

Instead of feeding input, it is possible to create similar output, for example filesize. And rerun this test and compare what package has the best quality for filesize. Or see what package could produce the best thumbnail with the settings available. There are lots of follow-up questions.

I am grateful for the blogpost and code by Bertrand Le Roy, it was a great inspiration and timesaver.

Follow up ​

Resources ​

Inspiration:
.NET Core Image Processing

Packages:
PhotoSauce