I am using C# and want to save images using JPEG format. However .NET reduces quality of the images and saves them with compression that is not enough.
I want to save files with their original quality and size. I am using the following code but compression and quality are not like the original ones.
Bitmap bm = (Bitmap)Image.FromFile(FilePath); ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders(); ImageCodecInfo ici = null; foreach (ImageCodecInfo codec in codecs) { if (codec.MimeType == "image/jpeg") ici = codec; } EncoderParameters ep = new EncoderParameters(); ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)100); bm.Save("C:\\quality" + x.ToString() + ".jpg", ici, ep);
I am archiving studio photos and quality and compression is very important. Thanks.
The best compression ratio to retain image quality is 10:1. If you're looking to reduce the file size of your photographs while keeping image quality, this is the maximum compression ratio you want to shoot for.
While JPEG compression can help you greatly reduce the size of an image file, it can also compromise the quality of an image - and if you aren't careful, there may not be any recovery. It is for this reason that we recommend saving your images in a lossless format such as TIFF.
The .Net encoder built-in to the library (at least the default Windows library provided by Microsoft) is pretty bad:
http://b9dev.blogspot.com/2013/06/nets-built-in-jpeg-encoder-convenient.html
I'm now using an approach outlined here, that uses ImageMagick for the resize then jpegoptim for the final compression, with far better results. I realize that's a partial answer but I'll expand on this once time allows.
ImageMagick is the best choice I've found so far. It performs relatively solid jpeg compression.
http://magick.codeplex.com/
It has a couple downsides:
It's better but not perfect. In particular, its Chroma subsampling is set to high detail at 90% or above, then jumps down to a lower detail level - one that can introduce a lot of artifacts. If you want to ignore subsampling, this is actually pretty convenient. But if you wanted high-detail subsampling at say, 50%, you have a larger challenge ahead. It also still won't quite hit quality/compression levels of Photoshop or Google PageSpeed.
It has a special deployment burden on the server that's very easy to miss. It requires a Visual Studio 2008 SDK lib installed. This lib is available on any dev machine with Visual Studio on it, but then you hit the server for the first time and it implodes with an obscure error. It's one of those lurking gotchas most people won't have scripted/automated, and you'll trip over it during some future server migration.
I dug around and came across a project to implement a C# JPEG encoder by translating a C project over:
http://www.codeproject.com/Articles/83225/A-Simple-JPEG-Encoder-in-C
which I've simplified slightly:
https://github.com/b9chris/ArpanJpegEncoder
It produces much higher quality JPEGs than the .Net built-in, but still is not as good as Gimp's or Photoshop's. Filesizes also tend to be larger.
BitMiracle's implementation is practically identical to the .Net built-in - same quality problems.
It's likely that just wrapping an existing open source implementation, like Google's jpeg_optimizer in PageSpeed Tools - seemingly libjpeg underneath, would be the most efficient option.
ArpanJpegEncoder appears to have issues once it's deployed - maybe I need to increase the trust level of the code, or perhaps something else is going on. Locally it writes images fine, but once deployed I get a blank black image from it every time. I'll update if I determine the cause. Just a warning to others considering it.
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