TurboJPEG

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DRC
Posts: 6
Joined: Sun Aug 11, 2019 9:15 pm
Country: United States

TurboJPEG

Post by DRC »

Hi. I'm the principal developer and sole maintainer of libjpeg-turbo, which provides the TurboJPEG API that I presume GraphicConverter is using whenever users select the "TurboJPEG" option. My question is: why is there even an option for that? The options dialog says "Lossless JPEG cropping is only supported with JPEG 6c", but that isn't true. libjpeg-turbo supports lossless cropping with both the TurboJPEG and libjpeg APIs. Our implementation of the libjpeg API, in fact, supports all of the lossless transformation options that libjpeg v9d supports. The TurboJPEG API supports the most popular lossless transformation options. I'm just trying to understand what deficiencies you perceived in libjpeg-turbo that prompted you to pass this decision on to your users.
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forum_adm
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Joined: Fri Dec 23, 2016 9:41 am
Location: Germany
Country: Germany

Re: TurboJPEG

Post by forum_adm »

Hi,

I found no way to estimate the original used compression rate with TurboJPEG. That is currently the main reason for the option.

I need the following values for a preview of the lossless cropping:
cinfo.max_h_samp_factor;
cinfo.max_v_samp_factor;

Also, I have to use the standard JPEG code on the Apple Silicon.

Also, I have to use the standard JPEG code if the lossless codec is used.

Thorsten