Doesn’t get as float convert from sRGB to Linear in your miplevels.py? If you don’t want conversion, open it as int8.
On Sun, Jan 10, 2021 at 10:39 Søren Ragsdale <sor...@gmail.com> wrote: > I have "checker_float32_lin.tif", a simple RGBA black and white > checkerboard. Each black or white square is 8 pixels wide, and every pixel > value is either 0.0 or 1.0. > > I'm using OIIO to turn this float32 scene-linear TIFF into a uint8 sRGB > albedo texture: > > maketx --oiio -d uint8 --unpremult --colorconvert linear sRGB > checker_float32_lin.tif -o checker_uint8_sRGB.tx > > I've written miplevels.py (see attached) which prints the min, median, and > max values of the first color channel for each mipmap level of the texture. > Here's the output: > > $ python ~/scripts-dev/miplevels.py checker_uint8_sRGB.tx >> 0 512x512=262144 min=0.0 med=1.0 max=1.0 >> 1 256x256=65536 min=0.0 med=1.0 max=1.0 >> 2 128x128=16384 min=0.0 med=1.0 max=1.0 >> 3 64x64=4096 min=0.0 med=1.0 max=1.0 >> 4 32x32=1024 min=0.498039245605 med=0.498039245605 max=0.607843160629 >> 5 16x16=256 min=0.498039245605 med=0.498039245605 max=0.556862771511 >> 6 8x8=64 min=0.498039245605 med=0.498039245605 max=0.529411792755 >> 7 4x4=16 min=0.498039245605 med=0.505882382393 max=0.51372551918 >> 8 2x2=4 min=0.501960813999 med=0.505882382393 max=0.505882382393 >> 9 1x1=1 min=0.505882382393 med=0.505882382393 max=0.505882382393 > > > As the mipmaps decrease in size the median value converges on 0.5. Except > this is a sRGB texture. The value for 50% grey should be around 0.737 in > sRGB space. > > It appears maketx is converting the values from linear to sRGB then > scaling to create the mipmaps. When the source and destination color space > are specified I think maketx should scale in scene linear color space, > *then* convert to sRGB before saving each mipmap. > > Is this a bug? Is there a flag or workaround that I should know about? > > > https://paroj.github.io/gltut/Texturing/Tut16%20Mipmaps%20and%20Linearity.html > _______________________________________________ > Oiio-dev mailing list > Oiio-dev@lists.openimageio.org > http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >
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