[gdal-dev] 1 bits per pixel tif image io driver

[Frank Warmerdam]

mario beaulieu wrote:
> Hi, i am a newbie.
>  
> Is it possible to load 1 bit per pixel image (1BPP) with gdal since 
> GDALDataType 
> <http://www.gdal.org/gdal_8h.html#22e22ce0a55036a96f652765793fb7a4> does 
> not enumerated this type of image?

Mario,

GDAL will automatically treat 1bit TIFF files as 8bit which happen to only
have pixel values 0 and 1.  In most cases it will also treat 0 and 1 as having
pseudocolor table entries to provide proper color and it will report metadata
indicating that NBITS=1.

eg.

warmerda at gdal64[53]% gdalinfo misc/fax2d.tif --debug off
Driver: GTiff/GeoTIFF
Files: misc/fax2d.tif
Size is 1728, 1082
Coordinate System is `'
Metadata:
   TIFFTAG_SOFTWARE=fax2tiff
   TIFFTAG_XRESOLUTION=204
   TIFFTAG_YRESOLUTION=98
   TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)
Image Structure Metadata:
   COMPRESSION=CCITTFAX3
   INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (    0.0,    0.0)
Lower Left  (    0.0, 1082.0)
Upper Right ( 1728.0,    0.0)
Lower Right ( 1728.0, 1082.0)
Center      (  864.0,  541.0)
Band 1 Block=1728x1082 Type=Byte, ColorInterp=Palette
   Image Structure Metadata:
     NBITS=1
   Color Table (RGB with 2 entries)
     0: 255,255,255,255
     1: 0,0,0,255

So, yes, you can work with 1BPP images.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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