Bug 58037 - Image.Save(Stream, encoder, perameters) does not use compression level
Summary: Image.Save(Stream, encoder, perameters) does not use compression level
Status: NEW
Alias: None
Product: Class Libraries
Classification: Mono
Component: System.Drawing ()
Version: 5.0 (2017-02)
Hardware: PC Linux
: --- normal
Target Milestone: Untriaged
Assignee: Bugzilla
Depends on:
Reported: 2017-07-10 08:55 UTC by Roman
Modified: 2017-07-10 08:55 UTC (History)
1 user (show)

Is this bug a regression?: ---
Last known good build:

Example project (9.95 KB, application/gzip)
2017-07-10 08:55 UTC, Roman

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Description Roman 2017-07-10 08:55:02 UTC
Created attachment 23429 [details]
Example project

Hello Guys! I work with pictures with jpeg format.
I need draw some logo over source image and tha save image to jpeg without compressing (high quality).
So my code:

            using(Image img = Image.FromStream(openFileDialog1.OpenFile())) //source image has size 298 000 bytes
                using (MemoryStream memStream = new MemoryStream())
                    ImageCodecInfo jpegEncoder = GetEncoder(ImageFormat.Jpeg);
                    System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
                    EncoderParameters myEncoderParameters = new EncoderParameters(1);
                    EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, 100L); //I can use 50L, 100L, 75L but it's not difference what number I direct - result is equal always
                    myEncoderParameters.Param[0] = myEncoderParameter;
                    img.Save(memStream, jpegEncoder, myEncoderParameters);
                    byte[] buff = memStream.ToArray();
                    Console.WriteLine("Size = {0}", buff.Length);          //result image has size 38 900 bytes

        private ImageCodecInfo GetEncoder(ImageFormat format)
            ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();
            foreach (ImageCodecInfo codec in codecs)
                if (codec.FormatID == format.Guid)
                    return codec;
            return null;

It's not difference what level quality I set, because result will be equal always. Result image is compressed with losing quality.
But in OS Windows it works excellent.
Maybe must I try a GTK-Sharp/Cairo for resolving this issue?