Feature request #10886

relative color tables for raster data

Added by Otto Dassau almost 6 years ago. Updated about 3 years ago.

Status:Open
Priority:Normal
Assignee:-
Category:Symbology
Pull Request or Patch supplied:No Resolution:
Easy fix?:No Copied to github as #:19254

Description

Hi,

I would nice, to be able to create relative color tables for raster data in QGIS and save them for other layers. Newly defined gradient color ramps end up in a color table with fix values:

for example:

  1. QGIS Generated Color Map Export File
    INTERPOLATION:INTERPOLATED
    6.916,0,191,191,255,6.916000
    120.812,0,255,0,255,120.811600
    234.707,255,255,0,255,234.707200
    348.603,255,127,0,255,348.602800
    462.498,191,127,63,255,462.498400
    576.394,20,20,20,255,576.394000

it would be great to save it as relative color values, as defined in the gradient color ramps dialog.

  1. QGIS Generated Color Map Export File
    INTERPOLATION:INTERPOLATED
    0%,0,191,191,255
    10%,0,255,0,255
    30%,255,255,0,255
    60%,255,127,0,255
    80%,191,127,63,255
    100%,20,20,20,255

and even better would be the option to create a mixed color table with fix values and percentage.

  1. QGIS Generated Color Map Export File
    INTERPOLATION:INTERPOLATED
    0,0,191,191,255
    60,0,255,0,255
    30%,255,255,0,255
    300,255,127,0,255
    80%,191,127,63,255
    100%,20,20,20,255

Is it possible to define such color tables in a text file and import it for
a raster layer? Or how would this be done?

Thanks a lot
Otto

History

#1 Updated by Paolo Cavallini almost 6 years ago

also the reverse should be done: currently when applying a colour ramp to a raster, this gets stretched from min-max, which is not always appropriate (e.g. DTM ramps should be applied as absolute values, so that top of hills should not be white).
In short, I think we should extend our model for ramps, allowing users to define both absolute and relative ramps, both when creating and when applying them.
GRASS could be a good guide for this.

#2 Updated by Giovanni Manghi about 3 years ago

  • Easy fix? set to No

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