Legacy ImageMagick Discussions Archive

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...

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...

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...

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...

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?

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 secon...

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: roseInt...

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.

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 ...

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...

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...

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...

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...

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...

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: -colorsp...