![]() Of course, I imagine you'd get a much better result if you were starting with a lossless image to begin with rather than an already-compressed JPEG. ![]() So all said, yes, I think you could integrate lossiness using a similar approach, but if you wanted the optimal combination for a given quality target, it probably wouldn't come from using the exact algorithm in jpegultrascan. I think you'd need to keep track of more than just the best combination though if you were interested in maximizing how many bits you could drop. When I was first testing it out, I wasn't sure I'd be able to iterate through all combinations in a reasonable amount of time, so I was looking into ways to estimate the best combinations by looking at the information content of adjacent bits. To be fast, you would ideally want a way of performing psychovisual calculation on the scans rather than the entire image, though I'm not sure if that's possible. However, what you could do is estimate the value of each entire scan to see if you could omit it entirely and still preserve psychovisual integrity. The spatial map doesn't lend itself directly to the lossy approach since you can't define different plane splits for spatial sub-sections of the image. In addition, in crunching JPEGs in this way, I found several bugs in mozjpeg that I'd rather have resolved before further development. 's description is ' This installer database contains the logic and data required to install ActivePerl 5.22.2 Build 2202 (64-bit). I have part of a C implementation, but the libjpeg API is a bit of a mess, so I haven't finished it. What is and developed by ActiveState according to the version information. It also supports certain obscure JPEG types such as CMYK.Īs mentioned in the README, I recommend using it with both the IJG version and mozjpeg version of jpegtran (and -t enabled) to get the best compression the fastest. It can generate files with a large number of scans, but I haven't run into compatibility problems thus far. ![]() With my files, I've seen an additional 5-10% file size savings over jpegrescan. Due to its exhaustive nature, it's slower than jpegrescan, which only searches a predetermined set of scan combinations, but not as slow as many PNG recompressors.
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