If the quantization tables follow the standard trend of limited compression in the low-frequency components rising to moderate compression in the high-frequency components, then the approximate quality factor may indeed give one an idea as to how the overall quality may appear. In the question What are the best image viewers for Windows Irfanview is ranked 2nd while XnView is ranked 3rd. Therefore, as an incredibly rough approximation, a calculation has been made for each source to derive the closest / approximate IJG quality factor for a given table. 79 17 When comparing XnView vs Irfanview, the Slant community recommends Irfanview for most people. So, what about other digicams / software editors that didn't use the IJG scaling method? People always love to make comparisons, and comparing multiple 64-element matrices is not intuitive to the average person. If we know that a given program has used the IJG scaling method, then we can indeed make a comparison, because all numbers in the matrices will move according to the algorithm in a similar manner. Just to say that I managed make XnConvert work to embed the sRGB profile. That said, many software programs and some digicams are indeed using scaled versions of this standard table. Ask for help and post your question on how to use XnView MP. All common picture and graphics formats are supported (JPEG, TIFF, PNG, GIF, WEBP, PSD, JPEG2000, OpenEXR, camera RAW, HEIC, PDF, DNG, CR2). XnView is one of the most stable, easy-to-use, and comprehensive photo editors. A quality factor of 100 does not mean Lossless compression! Instead, it generally represents the quality factor that will generate the highest quality compressed image with the provided scaling algorithm. Description XnView MP is a versatile and powerful photo viewer, image management, image resizer. This is NOT a percentage! It is merely a number from 1-100 representing the scaling factor used in generating the table. The IJG group has proposed a method of scaling these coefficients according to a “quality factor” scale. ![]() So, then why are “quality” numbers listed for each camera/software source? Many programs encode their JPEG images using quantization tables that are generated by scaling the coefficients in a “standard“ table that is provided in the ITU-T specification. Trying to make a comparison between a pair of matrices is not at all straightforward (or always possible). JPEG compression quality is actually defined by a pair of quantization tables (each with an array of 64 values). feature request: add 'sharpyuv' switch for webp output format. Calvin Hass (Comparing JPEG Quality » Important note about Quality Factors) wrote:It is extremely important that the reader understand that compression quality cannot truly be represented by a single value.
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