Search found 111 matches

by Dabrosny
2017-07-26T19:29:11-07:00
Forum: Bugs
Topic: [became suggest/request: write PNG as sRGB by deflt for DynamRng&Compat -edit] image gets darker&darker every round-trip
Replies: 43
Views: 26401

Re: image gets darker and darker every round-trip (involving png and linear images)

I am using ImageMagick-7.0.6-3-Q16-HDRI-x64-dll. HDR files are always linear. IM is reading and writing HDR correctly as colorspace RGB. Using -set colorspace sRGB on reading HDR would set incorrect colorspace. The problem is not with the hdr files. The problem is writing colorspace RGB (linear) dat...
by Dabrosny
2017-07-26T14:33:25-07:00
Forum: Bugs
Topic: [became suggest/request: write PNG as sRGB by deflt for DynamRng&Compat -edit] image gets darker&darker every round-trip
Replies: 43
Views: 26401

[became suggest/request: write PNG as sRGB by deflt for DynamRng&Compat -edit] image gets darker&darker every round-trip

On converting an image back and forth between a linear file format and a png format, it gets darker and darker (and btw has fewer and fewer unique colors) every round-trip due to spurious compound colorspace transformations / gamma operations. magick rose: rose.hdr (okay) magick rose.hdr rose.hdr.jp...
by Dabrosny
2017-07-25T08:40:39-07:00
Forum: Bugs
Topic: [We'll look to improve algo, time permitting -Magick] [workaround: -evaluate Log] count colors takes 13 times longer
Replies: 9
Views: 6258

Re: count unique colors (%k) takes 13 times as long on similar image

Thanks, @snibgo, I've also seen some images where 0.5/mean workaround doesn't do the trick. Without a reliable way of counting colors in even a small hdri image in IM, I've found that a command like this works quite well and quickly in cygwin (and it's easy to put this into a shell script): magick m...
by Dabrosny
2017-07-24T07:34:22-07:00
Forum: Bugs
Topic: [We'll look to improve algo, time permitting -Magick] [workaround: -evaluate Log] count colors takes 13 times longer
Replies: 9
Views: 6258

Re: count unique colors (%k) takes 13 times as long on similar image

Thanks, @snibgo, great workaround! I wonder if this idea could be incorporated into the way IM counts the colors to keep the time from exploding (without the user having to know how to do this workaround), at least until a hash table or bilinear search (as @magick mentions) could be implemented at s...
by Dabrosny
2017-07-23T19:30:24-07:00
Forum: Bugs
Topic: [We'll look to improve algo, time permitting -Magick] [workaround: -evaluate Log] count colors takes 13 times longer
Replies: 9
Views: 6258

Re: count unique colors (%k) takes 13 times as long on similar image

Thanks, @magick. Why would scaling the same small image with the same number of colors (265903) make it take 13 times as long? I'd be happy to scale it to where it is faster if I knew what scale that was :-) And @snibgo sees no such problem... could I be on the edge of some memory limit?
by Dabrosny
2017-07-23T14:16:12-07:00
Forum: Bugs
Topic: [We'll look to improve algo, time permitting -Magick] [workaround: -evaluate Log] count colors takes 13 times longer
Replies: 9
Views: 6258

[We'll look to improve algo, time permitting -Magick] [workaround: -evaluate Log] count colors takes 13 times longer

In some cases it takes an extremely long time (over 3 minutes) to calculate the number of unique colors for a very small (512x768) hdri image, while in other cases of just a slightly different version of the image, it takes "just" 15 seconds. In this case it takes "just" 15 seconds: time magick www....
by Dabrosny
2013-10-31T13:33:17-07:00
Forum: Bugs
Topic: Possible bug: -intensity has no effect on -white-threshold?.
Replies: 2
Views: 2406

Possible bug: -intensity has no effect on -white-threshold?.

The -intensity setting appears to have no effect on the result of applying some of the operators they are said to affect, for example the -white-threshold operator: imh convert rose: -intensity rec709luminance -white-threshold 32768 -format "%[colorspace] %[fx:mean]\n" -write info: roseIntLumINANCE....
by Dabrosny
2013-10-31T13:17:29-07:00
Forum: Developers
Topic: IM Example Contributions (How To)
Replies: 8
Views: 39257

Re: IM Example Contributions (How To)

anthony wrote:Would you be willing to to take it over, and migrate to a wiki format?
That would be a lot of work, but my life has sort of moved on to other things.
I'm afraid I can't take that on right now.
anthony wrote:I have been doing this for about 12 years, and I am feeling it.
And neither can you; I understand.
by Dabrosny
2013-10-31T12:50:10-07:00
Forum: Developers
Topic: -list intensity
Replies: 12
Views: 11646

Re: -list intensity

Here are some simple tests using a gradient: in 6.8.7.5 beta Q16 You're doing a lot of tests but not testing the actual effect of the -intensity setting on the resulting image (the mean of the data at least), for starters because the image is *already* grayscale. And you can't really compare final ...
by Dabrosny
2013-10-31T07:05:25-07:00
Forum: Developers
Topic: -list intensity
Replies: 12
Views: 11646

Re: -list intensity

Yes, you are right. -intensity only works on processing that converts the image to grayscale internally (or externally). Those listed functions convert the image to grayscale and then use the grayscale image to get statistics before thresholding or histogram processing. I will try -intensity ... -t...
by Dabrosny
2013-10-30T21:02:46-07:00
Forum: Developers
Topic: -list intensity
Replies: 12
Views: 11646

Re: -list intensity

Can someone clarify the effect of the -intensity setting on various operations on an image when the image is in a colorspace other than sRGB? E.g. will -intensity rec709luminance actually calculate a luminance to be used in the operation, or even any linear quantity at all, as opposed to a weighted...
by Dabrosny
2013-10-30T12:29:48-07:00
Forum: Developers
Topic: -list intensity
Replies: 12
Views: 11646

Re: -list intensity

Perhaps more importantly than my previous post, I'm not sure why -grayscale rec709luma won't in general produce a rec709luma, and why the user has to know to make sure their image is specifically in the sRGB colorspace before they invoke this, or before they invoke *any* -grayscale operator, if they...
by Dabrosny
2013-10-30T06:55:45-07:00
Forum: Developers
Topic: -list intensity
Replies: 12
Views: 11646

Re: -list intensity

Can we please remove -intensity rec601luminance rather than setting it in stone? There is really no such thing as "rec601 luminance", and certainly not one using these rec601 *luma* coefficients, which aren't intended to be applied to a *linear* RGB at all; doing so does not make sense and does not ...
by Dabrosny
2013-10-28T05:44:02-07:00
Forum: Developers
Topic: IM Example Contributions (How To)
Replies: 8
Views: 39257

Re: IM Example Contributions (How To)

It would be nice if the examples, and even more so, the main documentation pages like command-line-options.html, were in a wiki. Editing could be limited to logged-in users to minimize vandalism. I've seen a number of small errors that I could have simply fixed (and if I happened to make a mistake s...
by Dabrosny
2013-10-28T05:37:10-07:00
Forum: Bugs
Topic: possible bug -intensity IM 6.8.7.3 Q16 Mac OSX
Replies: 4
Views: 4221

Re: possible bug -intensity IM 6.8.7.3 Q16 Mac OSX

Is the following bug related? Otherwise I'll post it separately. The rose: pseudoimage in its defauilt sRGB has a mean of 0.41, and as linear it has a mean of about 0.2. imh convert -intensity rec709luminance -format "%[fx:mean] %[channels] %[gamma]\n" rose: -depth 16 -write info: -colorspace rgb -w...