Re: non-color-scaled rgbimage plots

[Dima K. <gn...@di...>]

sfeam <sf...@us...> writes:

> On Monday, 14 August 2017 21:13:00 Dima Kogan wrote:
>> Hi. These days a common plotting use case for me is to draw an image
>> from a file, with some data plotted on top of it. I do something like
>> this:
>>
>>   plot "xxx.png" binary filetype=auto flipy with rgbimage, "yyy" with points palette, ...
>>
>> This works OK. There's an annoyance however: the points in "yyy" have a
>> 3rd column, rendered as a color, and I want gnuplot to autoscale these
>> colors. But the pixels in "xxx.png" also have colors and gnuplot
>> interprets these colors as data too, and these 0-255 color values are
>> included in the autoscaling along with the 3rd column in "yyy". So for
>> instance, if the 3rd column in "yyy" is in [0-1], then the image is
>> plotted normally, but the "yyy" points all look black. Conversely, if
>> the points in "yyy" are in [10000-20000], then the points all look
>> yellow and the image is all black.
>>
>> Is there a way to instruct gnuplot to just plot the image as is, without
>> trying to interpret the pixel colors as data? If not, can we add such an
>> option? The current behavior is definitely good for some use cases, but
>> not for all of them.
>
> Right now the program ignores the "noautoscale" keyword for image plots.
> I'm not sure what would happen if that were to change.
> If you experiment with the code, that's where I suggest starting.

"noautoscale" applies to the whole plot, does it not? I think what would
be most appropriate here is some sort of "origcolors" option applicable
only to rgbimage/image data sources. So autoscaling would still apply,
but would ignore "origcolors" data. Does that make sense?