fmw42 wrote:The rings image is grayscale under IM 22.214.171.124 and higher and not sRGB.
I thought the image is "sGray" and so I use "-set colorspace sRGB" (not "-colorspace sRGB") before "-colorspace LUV" and "-colorspace LAB". Is it causing the troubles?
Your LUV images seem not having any color cast.
IM is now interpreting grayscale images as linear gray, since IM 126.96.36.199 and not sGray. The latter would likely have gamma=0.4545 and this image shows gamma=1 in IM 188.8.131.52.
Format: PNG (Portable Network Graphics)
Print size: 13.8889x13.8889
Base type: Grayscale
Rendering intent: Undefined
I don't see any colorcast. But I do not like how much contrast the result has. That does not look reasonable to me, though I am not an expert on colorspace and especially LUV.
If I do the same in non-hdri, I get more reasonable looking results from LUV, but you are right in that it has a bluish color case.
convert rings_lg_orig.png -colorspace sRGB -colorspace LUV
-resize 25% -alpha off +repage -colorspace sRGB -quality 95% rings_sm_luv3_nonhdri.png
convert rings_lg_orig.png -colorspace sRGB -colorspace LAB
-resize 25% -alpha off +repage -colorspace sRGB -quality 95% rings_sm_lab3_nonhdri.png
So HDRI mode (earlier post) is producing a worse result, but non-HDRI mode does not look right either due to the bluish color where it should be pure gray.