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Histogram of a selection

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    #1

    Histogram of a selection

    I'm considering this as a request, but I'm not completely sure that this function isn't already there in the program and I just can't see it.

    I want the histogram to be computed from the selection, if it has been defined, instead of the entire picture.

    1) to allow to examine clipping in selected shadow or highlight areas,
    2) decrease the time needed to compute a histogram,
    3) exclude large areas of a single color that we have no interest in.

    For example, if I have a high dpi scan that includes a white or black background that has not yet been cropped away, I am unable to see the distribution of light as well because there is a large peak at one end of the histogram, and the real data is squished at the very bottom with little visible variation.
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    #2
    How about making a selection of the pertinent area and then call a plugin, like Alois Zingl's SmartCurve

    (http://members.chello.at/easyfilter/curves.html).

    You get a histogram and much much more. All for free.

    currently running 4.56 / 32 bit

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      #3
      Thank you for the recommendation. The plugin is remarkably good, and easy to get adjusted to. I can only have the plugin work on a selection in a very recent IV version, but I can still examine different areas if I drag the preview window. I like how the primary colors are all visible at the same time for easy alignment.

      The plugin becomes accessible under Image -> Effects -> 8BF Filters -> Dialog with all filters, which is a bit long but ok, since I don't necessarily have to leave the dialog to make a new selection. If the built-in histogram could be improved like I suggested, that could be a quick way.

      Also I'd like to see different scale on the vertical axis. Or, if that cannot be clearly implemented, perhaps the top and bottom most colors can be ignored when computing the scale. This is to avoid the histogram being squished in the presence of clipping at either end, and becoming quite useless. I think Photoshop 7 does exactly this. Perhaps clipped columns could be painted red or just the top pixel of each, to indicate that they've been cut off.

      Sorry for the OT. I see you also have 32-bit Windows... Do we have 48-bit color by now? I find that I can scan bigger images in Irfan than I can in Photoshop due to lack of memory.
      Last edited by j7n; 24.09.2013, 11:37 PM. Reason: Scale

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        #4
        Originally posted by j7n View Post
        ...
        Sorry for the OT. I see you also have 32-bit Windows... Do we have 48-bit color by now? I find that I can scan bigger images in Irfan than I can in Photoshop due to lack of memory.
        Sorry if I get your meaning wrong, here goes anyway (to the best of my knowledge) :

        (1) For scanning I use the software that comes with the scanner, so I can't comment on scanning with IV
        (2) 32-bit operating system and 48-bit images are not related.
        (3) Irfanview can display 48-bit images by internally converting them to 24bit. Thus only 24bit images are handed down to plugins. - I'm still looking for a small, free software that does just that

        currently running 4.56 / 32 bit

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          #5
          Not a histogram but a different visualization of color distribution that I find useful to look at clipping is Martin Vicanek's Color cube 8Bf filter

          Hint: Increase the opacity setting to view the whole color pixel cloud.

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