From: Robbie Carlton <robbie.carlton@...>
Date: 2005-10-12T21:39:21+09:00
Subject: Re: [QUIZ] [Solution] Text Image (#50)

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thank you very very much. I've been struggling with a problem in the
graphics library I'm using for lisp (lispworks capi library) which requires
me to generate a bitmap file from an array of pixels. I couldn't decipher
any of the specs I've found for the format because they go into loads of
extraneous detail about color tables and compression which I don't need to
know about. Your code is the clearest definition of the spec I need
(assuming it's correct). So thanks

On 10/12/05, Harold Hausman <hhausman@gmail.com> wrote:
>
> Hi,
>
> Best quiz yet. Er, well, quiz which held my attention longest anyway. :)
>
> My solution is um, less... elegant, than some of the others, but in a lot
> of
> ways, like a parent who mistakenly thinks their ugly child is cute I kind=
a
> like it. I don't really share my code a lot (maybe for obvious reasons)
> but
> I'm just so pleased with how easily ruby lets me hack things to high
> heaven
> and this one in particular makes me smile. Take special note that it only
> works on 24 bit .bmp files and put your hard hat on if you think you're
> going to feed anything but that into it. ;) Okay, enough blather, without
> further ado, the first code I've shared with you guys:
>
> #It only supports 24bit bmp files, and it even chokes on most of them ;)
> #It creates one character per pixel (which has obvious implications)
> #But it's 40 lines of pure ruby no lib use binary file up-hackery...
> #And quite frankly, thats what I do.
>
> MyPixel =3D Struct.new( 'MyPixel', :r, :g, :b )
>
> the_gradient =3D %w|D Y 8 S 6 5 J j t c + i ! ; : .|
> ###############PUT YOUR FILENAME
> HERE#########################################
> the_file =3D File.new('ducky.bmp', 'rb')
> the_file.read(2) #BM
> the_file.read(4).unpack('V')[0] #filesize
> the_file.read(4) #unused
> the_file.read(4).unpack('V')[0] #offset from beginning to bitmap data
> the_file.read(4).unpack('V')[0] #size of bitmap header
> image_x =3D the_file.read(4).unpack('V')[0] #width x in pixels
> image_y =3D the_file.read(4).unpack('V')[0] #height y in pixels
> the_file.read(2).unpack('v')[0] #planes?
> the_file.read(2).unpack('v')[0] #bits per pixel
> the_file.read(24) #unused
>
> the_bitmap =3D []
> puts "CRRRRUNCHHHH --- please wait, reading file..."
> image_y.times do |row|
> the_bitmap[row] =3D []
> image_x.times do |col|
> the_bitmap[row][col] =3D MyPixel.new( 0, 0, 0 )
> the_bitmap[row][col].b =3D the_file.read(1).unpack('c')[0]
> the_bitmap[row][col].g =3D the_file.read(1).unpack('c')[0]
> the_bitmap[row][col].r =3D the_file.read(1).unpack('c')[0]
> end
> end
>
> puts "output coming:"
> the_output =3D File.new('output.asciiart', 'w')
> (image_y-1).downto(0) do |row|
> image_x.times do |col|
> the_avg =3D
> (the_bitmap[row][col].b+the_bitmap[row][col].g+the_bitmap[row][col].r)/3
> the_output.write(the_gradient[the_avg>>4])
> end
> the_output.write("\n")
> end
>
>

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