Setting an Image File Values

[W. Watson]

Mike C. Fletcher wrote:

> W. Watson wrote:
> 
>> I have a 640x480 b/w bmp image file that can be converted to a dat 
>> file. I would like to convert the value of each pixel that is below 
>> say 120 units to exactly 40 units.
> 
> 
> ...
> 
>>   python -c "open('mask.dat','w').write(chr(40)*640*480)"
> 
> 
> Well, if you're going to take this as the baseline, then we can do some 
> pretty darn simple stuff indeed:
> 
>  >>> import string
>  >>> def createMask( threshold=120, target=40 ):
> ...     """Create 256-char mapping of destination characters"""
> ...     return string.maketrans( "".join( [chr(x) for x in 
> range(threshold)]), chr(target) * threshold )
> ...
>  >>> data = open( "p:\\drawcurve.py", 'rb' ).read() # mode 'rb' is 
> important! use 'wb' to write
>  >>> mask = createMask()
>  >>> data
> "'''Test of the glVertex function\r\n\r\nDrawing TT glyphs as Cubic 
> splines...\r\n\thttp://support.microsoft.com/support/kb/articles/q243/2/85.asp\r\n\r\n'''\r\nfrom 
> OpenGLContext import testingcontext\r\nBaseContext"
>  >>> data.translate( mask )
> '((((((((((((((((((((((x((((((((((((((((((((((((((y(((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((x(((((((((((((((((((((x((((((((((((x(' 
> 
>  >>> ord('x') # just to see why x and y show up...
> 120
> 
> Of course, most Python programmers, when faced with a problem like this 
> would turn to either PIL (Python Imaging Library) or Numpy (Numeric 
> Python), but if all you need is quick-and-dirty, there you go.
> 
> Have fun,
> Mike
Having only seen the example snipet I gave as an example of python coding, what you 
wrote comes as a real surprise. This reminds me of a programming language called APL. 
It really had odd syntax. What are >>>, ..., and all those {{{{{? Not to mention the 
120 at the end. The snipet suggests that a python program can be run as a command 
line (python -c) like Perl. I would have thought a multi-line program to be executed 
would look something like
    python -c {line 1, line 2, line 3, etc.} It looks like I need to look at some 
python examples to get a feel for what this is about.