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bitmap with bit depth 1

  • To: mathgroup at smc.vnet.net
  • Subject: [mg104399] bitmap with bit depth 1
  • From: "van der Burgt, Maarten" <Maarten.VanDerBurgt at icos.be>
  • Date: Fri, 30 Oct 2009 02:19:35 -0500 (EST)

Hallo,



Using Mathematica 7.0.1 for Windows, I want to create binary bitmap 
(Windows BMP format) images with a bit depth of 1 (generally grey scale 
or color bitmap images have a bit depth of 8 or 24)



Here is my data:



dat =RandomInteger[{0,1},{200,200}]



The image generated from it looks ok:



im = Image[dat,"Bit"]



The right mouse click on the image and selecting Image Mode indeed tells 
me the image is binary with a bit depth of 1 bit/Channel. As does:



{ImageChannels[im], BinaryImageQ[im],ImageType[im]}

{1,True,Bit}



But all the images exported:

Export["test1.bmp",im];

Export["test2.bmp",im, "ColorDepth"=AE1];

Export["test3.bmp",im, "BitDepth"=AE1];

Export["test4.bmp",im, "BitDepth"=AE1,"ColorDepth"=AE1];



are 8 bit greyscale images.

Saving the image via the right mouse click on the image and choosing 
=93Save Image As..=94 saves a 24 bit image.



I current solution is the use of another package to reduce the bit 
depth, but this is not satisfactory. 



Am I doing something wrong here or is Mathematica failing here?



On top of this, I cannot import these image back into mathematica:



Import["test4.bmp" ]

Import::fmterr: Cannot import data as \[NoBreak]BMP\[NoBreak] format. 
=87 =
<http://reference.wolfram.com/mathematica/ref/message/Import/fmterr.html>

$Failed



Any help is appreciated.



regards



Maarten




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