optional histogram sidebar for legends

[hamish]

Hi,

I notice that VisIt has a neat feature to its color legends that let you incorporate a cumulative | frequency distribution graph along side the main color-gradient. It would be neat if d.legend & ps.map had that sort of capability.

examples:

​https://wci.llnl.gov/codes/visit/media/gallery/large_gallery_34.jpg ​https://wci.llnl.gov/codes/visit/media/gallery/gallery_05.jpg

Hamish

[hamish]

it shouldn't be too hard:

look at how many pixels tall the FP legend is drawn on the display, then get freq. data from 'r.stats nsteps=', so one value per screen line, scale max width to equal the width of the legend box, then draw a series of color= horizontal lines on the display connected to the left size of the legend (other side from the text). -f is already used so I guess -d for 'distribution'.

Is there any demand for cumulative? or is histogram enough?

Hamish

[hamish]

Hi,

legend histogram sidebars added to d.legend in trunk with r60093.

-- todo: support for CELL maps and constrained range=s.

For CELL maps we can perhaps interpolate between dist_stats->mincat and dist_stats->maxcat ?

I'm not sure how to get r.stats to deal with constrained range= while retaining pixel-height number of bins. Any ideas?

Hamish

[hamish]

demo of new functionality

[hamish]

Hi,

I've added to this ticket a screenshot of the new functionality.

​https://trac.osgeo.org/grass/attachment/ticket/1049/dleg_histo.png

shown is a horizontal legend for elevation.10m from Spearfish drawn with a histogram (-d flag), flipped left-right (-f flag, but setting at= as max,min has the same effect [wxGUI currently seems to be sorting at=, so that isn't working from the mouse]), and since I set the data units= with r.support the legend now displays "meters" too without needing a separate call to d.text.

the color rules there are a new addition as well, "roygbiv". In the screenshot r.colors was run with the -e flag so the color scaling is set to equal areas under the histogram curve instead of a linear color transition from min to max.

have fun, Hamish

[hamish]

horizontal cats legend with histogram

[hamish]

histogram support for categorical legends added in trunk with r60138.

screenshot:

​https://trac.osgeo.org/grass/attachment/ticket/1049/dleg_histo_soils.png

note there's a rendering bug in D_box_abs() + the PNG driver wrt subpixel rounding or closing-strokes. (run xmag on the right end of the legend in the screenshot)

Hamish

[annakrat]

This seems to be completed.