[gdal-dev] More information to understand ColorTables in GeoTiffs

Fri Mar 8 19:52:02 PST 2013

Frank,

Thanks for the response.

I've tried variations of [] and (), with and without alpha (3 or 4 values), and with various values ranging from 0 to 255. They all have failed so it seems i'm doing something fundamentally wrong.

Traceback (most recent call last):
  File "makecolortable.py", line 13, in <module>
    c.CreateColorRamp(1,n,65535,m)
  File "/usr/lib/python2.7/dist-packages/osgeo/gdal.py", line 1117, in CreateColorRamp
    return _gdal.ColorTable_CreateColorRamp(self, *args)
TypeError: not a sequence

Traceback (most recent call last):
  File "makecolortable.py", line 11, in <module>
    n = c.SetColorEntry(1,[0,0,0])
  File "/usr/lib/python2.7/dist-packages/osgeo/gdal.py", line 1113, in SetColorEntry
    return _gdal.ColorTable_SetColorEntry(self, *args)
TypeError: Invalid values in ColorEntry sequence 

import numpy as np
import gdal

driver = gdal.GetDriverByName('GTiff')
dst_ds = driver.Create('testcolor.tif', 100, 100, 1, gdal.GDT_UInt16)

band = dst_ds.GetRasterBand(1)
band.SetRasterColorInterpretation(gdal.GCI_PaletteIndex)

c = gdal.ColorTable(gdal.GCI_PaletteIndex)
n = c.SetColorEntry(1,[0,0,0])
m = c.SetColorEntry(65535,[0,0,0])
c.CreateColorRamp(1,n,65535,m)
band.SetColorTable(c)

--nix

On 2013/03/08, at 19:09, Frank Warmerdam <warmerdam at pobox.com> wrote:

> On Fri, Mar 8, 2013 at 2:05 PM, Robert Nix <robert at urban4m.com> wrote:
>> Let me adjust my question. I changed the color-table code to:
>> 
>> c = gdal.ColorTable(gdal.GCI_PaletteIndex)
>> n = c.SetColorEntry(1,[255,128,0,0])
>> m = c.SetColorEntry(65535,[0,128,255,255])
>> c.CreateColorRamp(1,n,65535,m)
>> band.SetColorTable(c)
>> 
>> 
>> I discovered that the 64K colors are due to the UInt16 (tested GDT_Byte and
>> got 255) so i realized that maybe i need to create a ramp?
> 
> Robert,
> 
> I will note that the TIFF format does not support "short colormaps".
> So if the type of the pixel is 8bit byte then the color table will be
> exactly 256 entries even if you only put in one color.  Frr UInt16 it
> will be 65536.  Most other colormap supporting formats do not impose
> this.
> 
>> But the above code fails with:
>> 
>> Traceback (most recent call last):
>>  File "makecolortable.py", line 14, in <module>
>>    n = c.SetColorEntry(1,[255,128,0,0])
>>  File "/usr/lib/python2.7/dist-packages/osgeo/gdal.py", line 1113, in
>> SetColorEntry
>>    return _gdal.ColorTable_SetColorEntry(self, *args)
>> TypeError: Invalid values in ColorEntry sequence
>> 
>> 
>> That sequence appears correct as all four values meet the short requirement,
>> (i think this is the code that produces the error):
>> 
>> if ( !PyArg_ParseTuple( $input,"hhh|h", &ce.c1, &ce.c2, &ce.c3, &ce.c4 ) ) {
>> 
>>  PyErr_SetString(PyExc_TypeError, "Invalid values in ColorEntry sequence
>> ");
> 
> 
> I think the problem is that you switched from tuples to lists (ie.
> from (r,g,b,a) to [r,g,b,a]).
> 
> Also, FYI, TIFF does not support alpha in colormaps.
> 
> Best regards,
> Frank
> 
>> --nix
>> 
>> On Mar 8, 2013, at 16:35, Robert Nix <robert at urban4m.com> wrote:
>> 
>> Hi,
>> 
>> I'm trying to add a color table to a 1-band UInt16 GeoTiff with Python as
>> follows:
>> 
>> import numpy as np
>> import gdal
>> 
>> driver = gdal.GetDriverByName('GTiff')
>> dst_ds = driver.Create('testcolor.tif', 100, 100, 1, gdal.GDT_UInt16)
>> 
>> band = dst_ds.GetRasterBand(1)
>> band.SetRasterColorInterpretation(gdal.GCI_PaletteIndex)
>> 
>> c = gdal.ColorTable(gdal.GCI_PaletteIndex)
>> c.SetColorEntry(1,(255,127,0,63))
>> band.SetColorTable(c)
>> 
>> a = np.random.randint(1,10,size=(100,100))
>> band.WriteArray(a)
>> 
>> dst_ds = None
>> 
>> 
>> The problem is that when i run gdalinfo on the testcolor.tif, it lists 65535
>> color table entries:
>> 
>> Driver: GTiff/GeoTIFF
>> Files: testcolor.tif
>>       testcolor.tif.aux.xml
>> Size is 100, 100
>> Coordinate System is `'
>> Image Structure Metadata:
>>  INTERLEAVE=BAND
>> Corner Coordinates:
>> Upper Left  (    0.0,    0.0)
>> Lower Left  (    0.0,  100.0)
>> Upper Right (  100.0,    0.0)
>> Lower Right (  100.0,  100.0)
>> Center      (   50.0,   50.0)
>> Band 1 Block=100x40 Type=UInt16, ColorInterp=Palette
>>  Color Table (RGB with 65536 entries)
>>    0: 1,0,0,255
>>    1: 1,0,0,255
>>    2: 0,0,0,255
>>    3: 0,0,0,255
>> ...
>>  65533: 0,0,0,255
>>  65534: 0,0,0,255
>>  65535: 0,0,0,255
>> 
>> 
>> What's going on … besides the fact that maybe i'm not understanding
>> color-tables? If it's clear i don't understand, is there a good resource for
>> understanding color-tables? Or must I go learn the source code (which i
>> really don't have to do)?
>> 
>> Thanks
>> --nix
>> 
>> 
>> 
>> _______________________________________________
>> gdal-dev mailing list
>> gdal-dev at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
> 
> 
> 
> -- 
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Software Developer

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