Which free software could acquire 48 bits color depth pictures from a scanner ?

Discussion in 'Scanners' started by Guilbert STABILO, Nov 16, 2008.

  1. Guilbert STABILO

    Ray Fischer Guest

    Not strictly true. Normalized floating point numbers actually do have
    24 bits of fraction plus 8 bits of exponent plus 1 bit of sign. It's
    done by inferring a leading one in the fraction that isn't actually
    represented.
    In practice chaining floating point operations while maintaining
    precision is really hard. If it's possible. Integer math is
    preferable almost always.
     
    Ray Fischer, Nov 17, 2008
    #41
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  2. Guilbert STABILO

    Steve Guest

    Back in the day when I was a DoD engineer, I had my own Cyber 170
    running NOS to play with. Of course, the laptop I'm using to write
    this can run rings around that thing.

    Steve
     
    Steve, Nov 17, 2008
    #42
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  3. Guilbert STABILO

    Ray Fischer Guest

    What "math processor"? "Deal with" in what way?

    Your question makes a couple of incorrect assumptions.
    1) That's there is a "math processor" that is different from the CPU.
    2) That the processing needs to be related to a "math processor".
     
    Ray Fischer, Nov 17, 2008
    #43
  4. Guilbert STABILO

    Ray Fischer Guest

    32 bits is still 32 bits whether it's foating point or fixed point or
    integer.

    You don't know what it means to maintain precision so I suggest that
    you stop worrying about it and leave it to us computer professionals.
     
    Ray Fischer, Nov 17, 2008
    #44
  5. Guilbert STABILO

    Steve Guest

    Ok, but for unnormalized (denormalized, non-normalized, whatever you
    want to name it) it's 23. I.e., they stole the sign bit from the
    fraction, not the exponent.

    The IEEE 754 floating point format only has 23 bits of fraction, not
    24. It has 8 bits of exponent and 1 bit of sign. You can infer all
    the bits you want but if they can't be "flipped" in a calculation then
    they are not useful if you want to represent the full range of
    available numbers.
    Yup. As I said in my post you responded to, using floating point math
    will often give different answers using even the same source code on a
    different compiler. In theory, it's possible to carry only one extra
    bit of significance through the calculations. In practice, not so
    easy.

    Steve
     
    Steve, Nov 17, 2008
    #45
  6. Guilbert STABILO

    Steve Guest

    Well, now it's completely obvious that you have no idea what you're
    talking about. If you think it's possible to take 32 bit integer data
    where the greatest values are higher than 2^24, convert it to 32 bit
    floating point, do some calculations on it, then convert back to
    integer and get the same results as if you had performed integer
    calculations then you are sadly mistaken.

    If you're a computer professional, I certainly hope I never come
    across anything you've created.

    Steve
     
    Steve, Nov 17, 2008
    #46
  7. Guilbert STABILO

    Steve Guest

    I should have said ^and always get the same results^ above. Because
    I'm sure Mr. Fischer would come up with some special case where the
    results would be the same.
     
    Steve, Nov 17, 2008
    #47
  8. Guilbert STABILO

    J. Clarke Guest

    Computers "do math" in whatever way the programmer decides.
     
    J. Clarke, Nov 17, 2008
    #48
  9. Guilbert STABILO

    J. Clarke Guest

    I note that you do not say "not since I got my doctorate". So you
    didn't impress your graduate committed any better than you're
    impressing us?
    Perhaps it is not, so one must conclude that you do not have such a
    degree.
     
    J. Clarke, Nov 17, 2008
    #49
  10. Guilbert STABILO

    Ray Fischer Guest

    Sigh. You guys have very little idea how computers do math.
     
    Ray Fischer, Nov 17, 2008
    #50
  11. Guilbert STABILO

    Ray Fischer Guest

    True, but FP numbers are almost always normalized.
    Plus a leading 1 bit.
    But IEEE floating point doesn't do the math in just 23 bits. It
    actually does it at least 26 bits and then normalizes and rounds to
    24 bits. The leading 1-bit is dropped and the remaining 23 bits of
    fraction are stored in the result.
     
    Ray Fischer, Nov 17, 2008
    #51
  12. Guilbert STABILO

    Ray Fischer Guest

    Except for 30 years as a professional software engineer and a BSCS and
    an MSCS. And those three quarters of computer architecture courses
    must have been worth something.
    Strawman. I never wrote any such thing.
    You have. I guess that it's running on your computer at this very
    moment.
     
    Ray Fischer, Nov 17, 2008
    #52
  13. Guilbert STABILO

    Ray Fischer Guest

    Didn't do a PhD. Stanford is very much oriented towards theoretical
    computer science while I'm more interested in software engineering.
    I stopped with my MSCS.
    Or one can conclude that you're an idiot who makes incorrect
    assumptions.
     
    Ray Fischer, Nov 17, 2008
    #53
  14. Guilbert STABILO

    Eric Stevens Guest

    All I can say is that that wasn't my experience about 1980ish.



    Eric Stevens
     
    Eric Stevens, Nov 17, 2008
    #54
  15. Guilbert STABILO

    Eric Stevens Guest

    I am an engineer with all that that entails with an interest in
    numerical computation. I encountered my first computer in 1960 and
    have been working with them ever since. Its more than 40 years since I
    wrote programs directly in machine code and probably 30 years since I
    used assembler. From the outset I wrote programs in Fortran and I was
    an early user of C .... . My programs worked which seems to make a
    nonsense of your claim that I have very little idea of how computers
    do math.



    Eric Stevens
     
    Eric Stevens, Nov 17, 2008
    #55
  16. Guilbert STABILO

    Eric Stevens Guest

    Why do you think I wrote that " ... an 8-bit floating point algorithm
    to emulate an 80 bit APU is likely to incorporate an accumulation of
    rounding off errors"?



    Eric Stevens
     
    Eric Stevens, Nov 17, 2008
    #56
  17. Guilbert STABILO

    Eric Stevens Guest

    Jeez! You must be young! :)

    Don't you remember when you were able to buy maths coprocessors to
    speed up up your PC? As you say, it is now built into the CPU but it
    is still there.

    See http://en.wikipedia.org/wiki/Intel_8087

    http://en.wikipedia.org/wiki/Motorola_68881



    Eric Stevens
     
    Eric Stevens, Nov 17, 2008
    #57
  18. Guilbert STABILO

    Eric Stevens Guest

    Actually, I think they were both announced in 1981. I do remember that
    Cromemco had 68000 based machines already available at the time of the
    IBM announcement (August 81).



    Eric Stevens
     
    Eric Stevens, Nov 17, 2008
    #58
  19. Guilbert STABILO

    Steve Guest

    That depends on the implementation. For instance, a PowerPC with an
    Altivec may do FP math different than an Intel Xeon which may be
    different than an old 80x86 with a math coprocessor which may be
    different than....

    You can run the same program on different hardware and get different
    results.

    Steve
     
    Steve, Nov 18, 2008
    #59
  20. Guilbert STABILO

    Steve Guest

    Apparently not.
    You certainly implied it when you said "32 bits is still 32 bits
    whether it's foating point or fixed point or integer." as a reponse to
    me writing that just saying you're doing "32 bit math" is meaningless
    unless you define the format.

    32 bits is 32 bits only to someone who's worried about storage space,
    network mandwidth, etc. To someone who's worried about doing math on
    those bits, you MUST know what those bit represent. So just saying
    that if "there's a 32 bit channel then the math is 32 bits" is
    meaningless without defining what those 32 bits represent. It could
    be integer, scaled integer, floating point, etc., all of which are
    completely different to a real software engineer.
    Ah, judging by the quality of some of the software out there, I
    wouldn't doubt it.

    Steve
     
    Steve, Nov 18, 2008
    #60
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