Search found 188 matches

by henrywho
2013-03-29T22:07:44-07:00
Forum: Bugs
Topic: [solved] Lab: "a" &" b" leaking into L in RGB round-trip?
Replies: 11
Views: 13065

Re: LAB: A&B channels leaking into L?

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. Even if it is converted to 8-bit RGB and got rounded or truncated, i...
by henrywho
2013-03-29T20:10:33-07:00
Forum: Bugs
Topic: [solved] Lab: "a" &" b" leaking into L in RGB round-trip?
Replies: 11
Views: 13065

Re: LAB: A&B channels leaking into L?

I thought A and B control the "hue" and "saturation" only... having no effect on luminance.
by henrywho
2013-03-29T18:27:23-07:00
Forum: Bugs
Topic: MinGW / Windows distribute-cache.c build err
Replies: 5
Views: 5387

Re: MinGW / Windows distribute-cache.c build err

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...
by henrywho
2013-03-29T15:30:15-07:00
Forum: Bugs
Topic: [solved] Lab: "a" &" b" leaking into L in RGB round-trip?
Replies: 11
Views: 13065

[solved] Lab: "a" &" b" leaking into L in RGB round-trip?

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% ...
by henrywho
2013-03-28T10:13:41-07:00
Forum: Users
Topic: Alternative to modulate command to increase Saturation
Replies: 40
Views: 55224

Re: Alternative to modulate command to increase Saturation

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.
by henrywho
2013-03-28T05:56:35-07:00
Forum: Users
Topic: Alternative to modulate command to increase Saturation
Replies: 40
Views: 55224

Re: Alternative to modulate command to increase Saturation

@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-contras...
by henrywho
2013-03-27T21:44:37-07:00
Forum: Bugs
Topic: L in HCL is not Luminance! (my error)
Replies: 11
Views: 13849

Re: L in HCL is not Luminance!

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...
by henrywho
2013-03-27T05:18:53-07:00
Forum: Users
Topic: Alternative to modulate command to increase Saturation
Replies: 40
Views: 55224

Re: Alternative to modulate command to increase Saturation

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 other than masks, tho...
by henrywho
2013-03-26T22:03:09-07:00
Forum: Users
Topic: Alternative to modulate command to increase Saturation
Replies: 40
Views: 55224

Re: Alternative to modulate command to increase Saturation

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?
by henrywho
2012-12-11T23:15:20-07:00
Forum: Digital Image Processing
Topic: 5 new interpolation kernels
Replies: 10
Views: 21852

5 new interpolation kernels

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

http://forum.doom9.org/showthread.php?t=166080
by henrywho
2012-12-01T09:12:24-07:00
Forum: Users
Topic: Oriental languages Japanese, chinese, Korean, etc
Replies: 3
Views: 5543

Re: Oriental languages Japanese, chinese, Korean, etc

try specifying a font like Arial Unicode MS or PMingLiU
by henrywho
2012-11-20T19:00:44-07:00
Forum: Users
Topic: Resizing working very slow
Replies: 7
Views: 9781

Re: Resizing working very slow

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.
by henrywho
2012-11-20T17:33:52-07:00
Forum: Developers
Topic: getting rid of Windows registry entries
Replies: 2
Views: 5132

Re: getting rid of Windows registry entries

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
by henrywho
2012-11-16T22:44:17-07:00
Forum: Digital Image Processing
Topic: Resize and resample in alpha-multiplied light
Replies: 5
Views: 28676

Re: Resize and resample in alpha-multiplied light

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...