Search found 188 matches

by henrywho
2017-06-01T21:55:01-07:00
Forum: Digital Image Processing
Topic: What's the best color space to preserve image naturalness?
Replies: 5
Views: 25580

Re: What's the best color space to preserve image naturalness?

I presume that you are talking about digitized images.

The best way to preserve a digitized image is to leave it in the original format untouched.

If you will be performing different operations on the image, the answer depends on the tool(s) you will be using.
by henrywho
2014-08-27T19:20:01-07:00
Forum: Users
Topic: convert - downscaling comic pages
Replies: 82
Views: 69858

Re: convert - downscaling comic pages

Nic, I am not really familiar with the composite operator. Would you mind pointing me to the explanation of the "complex" command line and the rationale of the blending using an alpha mask? (I guess it is meant to thicken the black lines by picking more from the gamma-adjusted downsize.)
by henrywho
2014-07-17T21:04:05-07:00
Forum: Digital Image Processing
Topic: BC-splines with 2C+B=1 are optimal for EWA resampling
Replies: 41
Views: 116902

Re: BC-splines with 2C+B=1 are optimal for EWA resampling

Yes, I always tell my friends to use linear light downsizing with EWA Catrom or Lagrange, while they keep using USM to (/hoping to) recover the highlight lost after downsizing in sRGB. EWA Catrom is an overkill in most cases, though.
by henrywho
2014-04-14T23:05:55-07:00
Forum: Users
Topic: What's the best way to do resize for radar image
Replies: 3
Views: 6804

Re: What's the best way to do resize for radar image

Any sample?

(BTW, should this post be in relocated to the Users forum?)
by henrywho
2013-09-21T09:09:37-07:00
Forum: Bugs
Topic: 6.8.6-10 32bit DLL compile not working under XP64
Replies: 3
Views: 5632

Re: 6.8.6-10 32bit DLL compile not working under XP64

Too bad that the support of 64bit compile under XP64 had been dropped ....
by henrywho
2013-09-20T20:53:03-07:00
Forum: Bugs
Topic: 6.8.6-10 32bit DLL compile not working under XP64
Replies: 3
Views: 5632

6.8.6-10 32bit DLL compile not working under XP64

ImageMagick-6.8.6-10-Q16-x86-dll.exe (18,305,076 bytes)

"The procedure entry point GetErrorMode could not be located in the dynamic link library KERNEL32.dll."
by henrywho
2013-05-09T21:02:01-07:00
Forum: Bugs
Topic: L in HCL is not Luminance! (my error)
Replies: 11
Views: 14091

Re: L in HCL is not Luminance!

magick wrote:We'll support HCL in perhaps a week or two. Stand by...
Is it implemented in 6.8.5.5? :o
by henrywho
2013-04-10T19:52:27-07:00
Forum: Users
Topic: Downsample JPEG to 72x72
Replies: 3
Views: 7434

Re: Downsample JPEG to 72x72

Depending on the image content, you may also want to refer to the resize algorithms and the gamma issues mentioned in: http://www.imagemagick.org/Usage/filter/nicolas/#downsample For example: convert in.jpg -colorspace RGB -filter LanczosRadius -distort Resize 1100x600! -density 72 -colorspace sRGB ...
by henrywho
2013-04-03T17:15:35-07:00
Forum: Bugs
Topic: ImageMagick 6.8.4 darkening grayscale images on convert
Replies: 22
Views: 24415

Re: ImageMagick 6.8.4 darkening grayscale images on convert

fmw42 wrote:That is reasonable, since RGB and sRGB were reversed then. So using -set colorspace sRGB in the older versions is like using -set colorspace RGB in the newer versions.
That's after the reversion of "-colorspace RGB" and "-colorspace sRGB"
by henrywho
2013-04-03T09:11:09-07:00
Forum: Users
Topic: Scaling scans of analog photo negatives
Replies: 5
Views: 7993

Re: Scaling scans of analog photo negatives

any sample image? :?
by henrywho
2013-04-03T01:22:28-07:00
Forum: Bugs
Topic: ImageMagick 6.8.4 darkening grayscale images on convert
Replies: 22
Views: 24415

Re: ImageMagick 6.8.4 darkening grayscale images on convert

I am not sure that process you mention will not work with grayscale images. It fails for me when the input gray images is already non-linear sRGB gray (as per the images for the above post). It worked a year ago when Imagemagick treated gray images (no matter grayscale or "color" images with gray s...
by henrywho
2013-04-02T20:16:51-07:00
Forum: Bugs
Topic: ImageMagick 6.8.4 darkening grayscale images on convert
Replies: 22
Views: 24415

Re: ImageMagick 6.8.4 darkening grayscale images on convert

"Gray problems" seem to pop up a while after the other. I try to avoid them by adding "-set colorspace srgb" immediately after the input image. So far it works.

Edit: oops... not for 6.8.4-5
by henrywho
2013-03-30T00:43:26-07:00
Forum: Bugs
Topic: [solved] Lab: "a" &" b" leaking into L in RGB round-trip?
Replies: 11
Views: 13312

Re: Lab: "a" &" b" channels leaking into L in RGB round-trip

snibgo wrote:Try non-integer arithmetic, ie IM with HDRI. Your three commands then give identical results.
I dun know that limiting would appear in this manner :lol:

I have an old 6.7.6 HDRI compile only. Do you know where we can find an updated windows HDRI compile?
by henrywho
2013-03-29T23:58:37-07:00
Forum: Bugs
Topic: [solved] Lab: "a" &" b" leaking into L in RGB round-trip?
Replies: 11
Views: 13312

Re: Lab: "a" &" b" channels leaking into L in RGB round-trip

henrywho wrote:Yes, I have to lose something, but that should be rounding, truncation or limiting. NOT overflowing to overall brightness
Just checked the formulae .... such "leaking" is built-in .... period .....
by henrywho
2013-03-29T23:47:49-07:00
Forum: Bugs
Topic: [solved] Lab: "a" &" b" leaking into L in RGB round-trip?
Replies: 11
Views: 13312

Re: Lab: "a" &" b" channels leaking into L in RGB round-trip

Even if it is converted to 8-bit RGB and got rounded or truncated, it should not change the overall "brightness". No. Lab can represent colours that RGB cannot, such as different tones of fully-saturated red. When you convert these colours to RGB, you have to lose something -- either the full satur...