Legacy ImageMagick Discussions Archive

That is correct. (Except that they are called a and b, not A and B.) And I thought "fully saturated" have different implications in "Lab" and "RGB". Under "Lab", no matter how we manipulate "a" and "b", "L" should not be affected...

I thought A and B control the "hue" and "saturation" only... having no effect on luminance.

Awesome, thanks! By the way, can you give the steps you use to build on MinGW + windows? I was having some issues due to pthread and such (which I ironed out using the pthread for windows port) but I want to check if there is a better / easier way I once worked out a way to compile it under mingw32...

Found something strange.... convert.exe -respect-parentheses \ rose: -set colorspace sRGB -colorspace LAB \ -channel R -separate placebo_%d.png convert.exe -respect-parentheses \ rose: -set colorspace sRGB -colorspace LAB \ -channel G -sigmoidal-contrast 9,50% \ -channel B -sigmoidal-contrast 9,50% ...

If it is a problem of "-separate", "b_0.png" should have been fine.

but "b_0.png" is wrong (in the same way) even if I put "RGB", "LUV", "HCL", etc. in place of "sRGB" in the middle.

@henrywho: if you want to increase saturation while leaving the L of Lab unchanged, the obvious way is to do it in Lab space. The a and b channels both record saturation as the distance from 0.5, that is a=b=0.5 (in the range 0 to 1) represents zero saturation. So apply the same "-sigmoidal-co...

I am using Win32 Q16 static compile: Version: ImageMagick 6.8.3-5 2013-02-24 Q16 http://www.imagemagick.org Copyright: Copyright (C) 1999-2013 ImageMagick Studio LLC Features: DPC OpenMP convert.exe rose: -set colorspace srgb -colorspace hcl -channel R -gamma 1 +channel -colorspace lab -channel R -s...

Actually, I am trying to increase the saturation so "-gamma 1.5" seems more appropriate.... except that I am looking for a way not to touch the pixels with high saturation.... something like "if saturation > threshold then untouch else increase it". Looking for some simpler way o...

Just tried something like:

convert.exe input.png -set colorspace srgb -colorspace hcl -channel G +sigmoidal-contrast 3.5,49% +channel -colorspace srgb output.png

Not bad.... but I need something asymmetric so as not to de-saturate the high-saturation areas. Do u guys have any idea?

For whoever interested, *.mp4 has posted five interpolation kernels in Doom9:

http://forum.doom9.org/showthread.php?t=166080

try specifying a font like Arial Unicode MS or PMingLiU

Agreed with fmw42.

A sharpened JPEG saved at a lower quality may have similar size as a smoother JPEG saved at a higher quality.... but looking much worse.

Or search in the following order:
1) same directory or specific subdirectory of convert.exe/magick.exe
2) environmental variable (e.g. MAGICK_CONFIGURE_PATH)
3) HKCU
4) HKLM

Must read: http://www.imagemagick.org/Usage/filter/nicolas/

Last week I was resampling some large web banners (with transparency) into small paletted (8bit) icons. I also ended up with flatten-then-resample: convert big_banner_with_alpha.png -set colorspace srgb +repage \ -colorspace lab -background white -flatten \ -define filter:window=Quadratic -define fi...