Fixes in html files and manifest from 2000
This commit is contained in:
1 parent
571c24ee73
commit
22931fa3eb
24 files changed
+315
-246
No files matched your search
+17
-17
@@ -14,7 +14,7 @@
|
||||
|
||||
## Try:
|
||||
|
||||
In a video window (white text on black background):
|
||||
In a terminal window (white text on black background):
|
||||
|
||||
``` <!---sh-->
|
||||
./try.sh
|
||||
@@ -33,7 +33,7 @@ The author recommended on linux/x86, glibc 2.0, libc4/5:
|
||||
|
||||
``` <!---make-->
|
||||
bmeyer: bmeyer.c
|
||||
CC -DY="__setfpucw(0x127f)" -O6 $? -o $@ -lm
|
||||
cc -DY="__setfpucw(0x127f)" -O6 $? -o $@ -lm
|
||||
```
|
||||
|
||||
However many compilers use `-O3` as the maximum level for `-O` optimization.
|
||||
@@ -74,9 +74,9 @@ This program is called `GLICBAWLS`
|
||||
Squares".
|
||||
|
||||
And that's exactly what this program does --- feed it a .PGM file
|
||||
(either raw [i.e. P5] or ASCII [i.e. P2]) on stdin, and it will
|
||||
output a compressed version to stdout. Feed it a compressed file
|
||||
on stdin, and it will decompress it to stdout --- as either raw or
|
||||
(either raw [i.e. P5] or ASCII [i.e. P2]) on `stdin`, and it will
|
||||
output a compressed version to `stdout`. Feed it a compressed file
|
||||
on `stdin`, and it will decompress it to `stdout` --- as either raw or
|
||||
ASCII .PGM, depending on what format it was compressed from. For
|
||||
example:
|
||||
|
||||
@@ -215,7 +215,7 @@ In short --- running it through the preprocessor and the
|
||||
pretty-printer will give you something that looks slightly less
|
||||
like line noise and slightly more like a C program, but unless you
|
||||
are a true wizard, it is unlikely to gain you any insights into
|
||||
what is actually going on....[^0]
|
||||
what is actually going on....[^1]
|
||||
|
||||
|
||||
### Bugs, Assumptions and TODO
|
||||
@@ -269,7 +269,7 @@ ordering. For each pixel, an expected value is calculated by creating a least
|
||||
squares predictor of order 12 based on all of the previously encoded/decoded
|
||||
pixels. However, the contribution of each pixel is weighted according to its
|
||||
[Manhattan-distance](https://en.wikipedia.org/wiki/Taxicab_geometry) from the
|
||||
current pixel, `D`. That weight used is `pow(0.8,D)`. [^1] [^2] [^3]
|
||||
current pixel, `D`. That weight used is `pow(0.8,D)`. [^2] [^3] [^4]
|
||||
|
||||
In a similar way, the prediction *errors* for all previous pixels
|
||||
are combined --- a weighted average (with weight `pow(0.7,D)`) of
|
||||
@@ -293,27 +293,27 @@ arithmetic decoder provides the information which half the actual
|
||||
value is in. In both cases, the interval borders are adjusted
|
||||
accordingly, the arithmetic coder/decoder updated, and the
|
||||
interval halving repeated until the precise value has been
|
||||
en/decoded[^4].
|
||||
en/decoded[^5].
|
||||
|
||||
|
||||
[^0]: Yes, this could be seen as a challenge....
|
||||
[^1]: Actually, the weight is `pow(0.8,D)/s`, where `s` is the sigma
|
||||
[^1]: Yes, this could be seen as a challenge....
|
||||
[^2]: Actually, the weight is `pow(0.8,D)/s`, where `s` is the sigma
|
||||
used for encoding/decoding the particular previous pixel. Dividing
|
||||
by `s` is a rather arbitrary action justified only by the
|
||||
improvement in results. Mathematically, I can only justify
|
||||
dividing by `s^2`, or not dividing at all....
|
||||
[^2]: Obviously, these least squares predictors are not calculated
|
||||
[^3]: Obviously, these least squares predictors are not calculated
|
||||
from scratch for each pixel. Some clever reuse of earlier
|
||||
results allows `O(1)` calculation, rather than the
|
||||
`O(previous_rows*columns)` this description would suggest.
|
||||
[^3]: As anyone who has ever tried local least squares knows from
|
||||
[^4]: As anyone who has ever tried local least squares knows from
|
||||
bitter experience, there is a lot of numerical instability
|
||||
associated with them. So `glicbawls` adds a bias towards an
|
||||
averaging predictor to the equation system the least squares
|
||||
predictor is calculated from. The weight that is given to
|
||||
this bias is constantly adjusted throughout coding/decoding,
|
||||
thus justifying the 'a' in `glicbawls`.
|
||||
[^4]: In the case of near-lossless coding, the interval is not
|
||||
[^5]: In the case of near-lossless coding, the interval is not
|
||||
necessarily *halved*, but rather split at a convenient point
|
||||
(the split points are chosen in such a way as to minimise the
|
||||
expected number of bits needed for coding). Also, the
|
||||
@@ -324,7 +324,7 @@ en/decoded[^4].
|
||||
### Photo Credit:
|
||||
|
||||
[Lavabus](lavabus.pgm) was taken by the judge, Landon Curt Noll.
|
||||
[Michael](michael.pgm) was provided by the author. [Lenna](%%REPO_URL%%/2000/bmeyer/lenna.glic) is a
|
||||
[Michael](michael.pgm) was provided by the author. [Lenna](lenna.glic) is a
|
||||
1972 Playboy centerfold (doesn't show very much).
|
||||
|
||||
- [michael.pgm](michael.pgm)
|
||||
@@ -333,11 +333,11 @@ en/decoded[^4].
|
||||
|
||||
- [lavabus.pgm](lavabus.pgm)
|
||||
|
||||
A bus that was trapped by lava from [Kilauea
|
||||
volcano](https://en.wikipedia.org/wiki/Kīlauea) in Hawaii, US. Nobody was
|
||||
A bus that was trapped by lava from [Kīlauea
|
||||
volcano](https://en.wikipedia.org/wiki/Kīlauea) in Hawaii, US. Nobody was
|
||||
in the bus at the time, BTW. Photo date: 1981.
|
||||
|
||||
- [lenna.glic](%%REPO_URL%%/2000/bmeyer/lenna.glic)
|
||||
- [lenna.glic](lenna.glic)
|
||||
|
||||
A November 1972 Playboy centerfold was scanned in long ago and has been used
|
||||
for image compression research since then. Playboy originally threatened to
|
||||
|
||||
Reference in new issue
Block a user