Gamma error in picture scaling
I&#x27;m not an expert, but I&#x27;ve dealt with my share of this working in film.  Color problems in image processing are everywhere.  Pre-multiplication and Alpha channels are another huge one.  A lot of professionals don&#x27;t even understand it and will brute-force compensate for problems instead of understanding the problem.  Here&#x27;s a posting from this week [1] from professionals who care about getting this stuff right trying to convert a tiff to jpeg without surprise colors shifts.<p>A summary is that you need to do almost all image modifications in a linear color space.  So you first need to back out any color tweaks made (for aesthetic or technical reasons), modify the image, then re-apply any tweaks.<p>Unfortunately, image files often aren&#x27;t tagged with their color space and might use a specific color space out of convention--but they could use something else.  Also, because it&#x27;s way harder to do the right thing, a lot of software just does the modifications ignoring color space.  Just think about how much slower and more memory a web page full of thumbnails would take to draw if you added in color space transformations?  For awhile, a lot of browsers added support but left them off by default (imagine if you designed your web page to look right in a broken color space and it was suddenly much slower and now looked wrong).  But a lot of software is slowly catching up.  Unfortunately, legacy software (like Photoshop) and legacy file formats might never change.<p>[1] <a href="http:&#x2F;&#x2F;lists.openimageio.org&#x2F;pipermail&#x2F;oiio-dev-openimageio.org&#x2F;2019-January&#x2F;001390.html" rel="nofollow">http:&#x2F;&#x2F;lists.openimageio.org&#x2F;pipermail&#x2F;oiio-dev-openimageio....</a>