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Re: bitmap with bit depth 1

• To: mathgroup at smc.vnet.net
• Subject: [mg104441] Re: [mg104399] bitmap with bit depth 1
• From: Patrick Scheibe <pscheibe at trm.uni-leipzig.de>
• Date: Sat, 31 Oct 2009 01:55:24 -0500 (EST)
• References: <200910300719.CAA27777@smc.vnet.net>

Hi,

has it to be a bmp? If not then

Image[Reverse@
  Table[If[(x^2 + y^2 - 1)^3 - x^2 y^3 > 0.0, 0, 1], {y, -2, 2, 
    4/255.}, {x, -2, 2, 4/255.}], "Bit"]
Export["~/tmp/binimg.pbm", %]
{ImageType[#], ImageChannels[#], ImageDimensions[#]} &@Import[%]

should help.

Cheers
Patrick

On Fri, 2009-10-30 at 02:19 -0500, van der Burgt, Maarten wrote:
> 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
> 
> 
> 

• References:
  • bitmap with bit depth 1
    • From: "van der Burgt, Maarten" <Maarten.VanDerBurgt@icos.be>