Ok, no problem. I will try to clarify what are my observations:
string myFileName = @"C:\picture.jpg"; MagickImage image = new MagickImage(); image.Save(myFileName); // no define-statement. in my example, the output is optimized. this is the default behaviour and I get a smaller filesize. MagickImage image = new MagickImage(); image.SetDefine(MagickFormat.Jpeg, "optimize-coding", false); image.Save(myFileName); // explicit optimize-coding=false. in my example, the output is optimized as well, although I set optimize-coding=false. The output is exactly the same as the default behaviour. I verified this with a md5-hash. MagickImage image = new MagickImage(); image.SetDefine(MagickFormat.Jpeg, "optimize-coding", true); image.Save(myFileName); // optimize-coding=true. in my example, the output is NOT optimized although I set optimize-coding=true. the filesize is bigger than the first two outputs (again, the first two are the exactly the same)