Legacy ImageMagick Discussions Archive

Not sure if it is something like rounding errors:

Win32 ImageMagick 6.7.8-10 2012-08-10 Q16 DLL convert rings_lg_orig.png -colorspace LUV -resize 25% -alpha off +repage -colorspace sRGB -quality 95% rings_sm_luv1.png convert rings_lg_orig.png -set colorspace sRGB -colorspace LUV -resize 25% -alpha off +repage -colorspace sRGB -quality 95% rings_sm_...

NicolasRobidoux wrote:I am convinced that linear light is "it" when downsampling. But I am not certain.

Me neither, especially after Anthony's comment that while linear RGB's intensity is linear, its colors are not.

I wonder how much these contrived tests really tell us. Sorry being off-topic. Actually I should have posted in another thread where Anthony talks about LAB and LUV. Even if they are too harsh sometimes, these contrived tests do help revealing abnormality. For example, the LUV-downsize above produc...

Henry: "Brasseur test" conclusion: stick to linear light when downsampling. Seems LUV works very well in Brasseur-Dalai test: convert gamma_dalai_lama_gray_tft.jpg -distort resize 50% -quality 95% -sampling-factor 1:1:1 dal_tft.jpg convert gamma_dalai_lama_gray_tft.jpg -set colorspace sRG...

NicolasRobidoux wrote:When I have a minute, I will change enhance.c so that sigmoidal-contrast not use a LUT in HDRI mode

Hope we will have an official HDRI compile.

It works again by adding "-set colorspace sRGB".

With 6.7.8-9 Win64 DLL, gray images appear to be causing troubles again: convert rings_lg_orig.png -alpha off -colorspace RGB -filter RobidouxSharp -distort resize 50% -colorspace sRGB -alpha off +repage -quality 95% test1.png convert rings_lg_orig.png -alpha off -evaluate POW 2.2 -filter RobidouxSh...

A small note that some ppls like to take BW (gray) photos but IM6 behaves weirdly with gray photos and -colorspace options. Better use -gamma with gray photos for the time being.

Are "LanczosRadiusN" and "LanczosSharpestN" available directly in IM6 or 7 now?

r u really upsizing by 1000 times?

Henry: I'll have to redo the downsampling tests with the newly fixed sigmoidal-contrast code. (IM7 is closest to fixed, and the fix is not complete for orthogonal resize methods with negative lobes.) Other things to do for a while. Remember to include this test case: http://www.4p8.com/eric.brasseu...

To add even more acutance (sth like edge sharpness), convert -density 288 image.pdf -filter lagrange -distort resize 25% -quality 95 -sampling-factor 1:1 image.jpg Linear RGB resize is mathematically more correct but this is probably counter-productive in this use case: convert -density 288 image.pd...

Hey, it's not fair. I am an amateur using defaults and you are THE expert using tuned parameters.

NicolasRobidoux wrote:

henrywho wrote:...
Let me try Avisynth+NNEDI3+EEDI3 tonight.

Thank you Henry.

Pure NNEDI3