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

[Jan Heckman]

Robert,
Afaik, you need a three tuple for the color info. See e.g.
http://osgeo-org.1560.n6.nabble.com/gdal-dev-tiff-with-colortable-loses-alpha-values-td3747611.html
.
It has a line giving an apparently working SetColorEntry() call without
also using CreateColorRamp() which just complicates things here.
For tuples in python,
http://docs.python.org/release/1.5.1p1/tut/tuples.html gives
a useful explanation.
Hope this helps a bit,
Jan

On Sat, Mar 9, 2013 at 4:52 AM, robert <robert at urban4m.com> wrote:

> 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
>
>
>
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/gdal-dev/attachments/20130310/3e47026a/attachment.html>