Re: Convert jpg with quality not properly

Hi, I used mozjpeg jpeg libray, and in the github, I found this issues: https://github.com/mozilla/mozjpeg/issues/181 <https://github.com/mozilla/mozjpeg/issues/181>.




> 在 2018年9月17日，上午10:18，YongdeGe <[email protected]> 写道：
> 
> I am comfused about the quality,  if the quality not store into Image Structure, why I use GraphicsMagick utils convert jpeg, but get the right quality when checked it. And there is some regulars for the quality when use the binding:
> 
> Expect Quality     Real Quality
> 70		   		34
> 80				50
> 88				70
> 90				76
> 91				78
> 92				80
> 
> Actually, I try another golang binding for testing, but get the same problem. But, I use ImageMagick to view the verbose, I notice that：Quality: 34 (approximate). As you said before, maybe there is no perperty for the quality.
> 
> 
> 
>> 在 2018年9月15日，下午9:47，Bob Friesenhahn <[email protected]> 写道：
>> 
>> On Sat, 15 Sep 2018, YongdeGe wrote:
>> 
>>> Thank you for your reply.
>>> 
>>> The golang binding (https://github.com/rainycape/magick) was not maintained for at least four years, and the binding use MagickCore api, and it call low api ImageToBlob with info{quality, format}.
>> 
>> I should mention that GraphicsMagick only stores quality in the ImageInfo structure so that it is only used when writing the image and is not an image property.  In the future it may also store it in the Image structure (as an image property).  I would not be surprised if ImageMagick has added a quality member to its Image structure.
>> 
>> Bob
>> -- 
>> Bob Friesenhahn
>> [email protected], http://www.simplesystems.org/users/bfriesen/
>> GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
>> 
>> 
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