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tech_info.txt
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tech_info.txt
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Technical information for developers, algorithms, code comments for sam2p
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Upsampling
""""""""""
Here is a figure about upsampling samples bits 1 -> 2 -> 4 -> 8:
0 -> 00 0
1 -> 11 3
00 -> 0000 0
01 -> 0101 5
10 -> 1010 10
11 -> 1111 15
0000 -> 0000 0000 0
0001 -> 0001 0001 17
0010 -> 0010 0010 34
...
1110 -> 1110 1110 238
1111 -> 1111 1111 255
A 1-bit image has a palette of 2 colors: #00 and #ff.
A 2-bit image has a palette of 4 colors: #00, #55, #aa and #ff.
A 4-bit image has a palette of 16 colors: #00, #11, #22, ... #ff.
An 8-bit image has a palette of 256 colors: #00, #01, #02, ... #ff.
Obsolete: Image metadata
""""""""""""""""""""""""
-- Width: uint
-- Height: uint
-- ColorSpace: enum (see later), determines PixBits
-- PixBits: 1..24
-- Origin: coord
-- Comment: string
-- FileFormat:
-- Predictor: enum (see later), same as PSLanguageLevel1 filter
/Predictor
1 -- no predictor
2 -- TIFF predictor 2 (horizontal differencing)
10 -- PNG predictor, None function
11 -- PNG predictor, Sub function
12 -- PNG predictor, Up function
13 -- PNG predictor, Average function
14 -- PNG predictor, Paeth function
15 -- PNG predcitor, individually chosen for each line
-- PredictorColumns: uint
-- PredictorColors: 1..3
-- PredictorBitsPerComponent: 1, 2, 4, 8
-- CompressionEffort: -1..9 (ZIP)
-- CompressionRecordSize: uint (RLE, Fax: K)
-- Compression: enum
0 -- None
1 -- LZW (PSL2 PDF1.0 LZWEncode filter EarlyChange=true, UnitLength=8
LowBitFirst=false)
2 -- ZIP (PSL3 PDF1.2 FlateEncode filter without options)
3 -- RLE (PSL2 PDF1.0 RunLengthEncode filter, similar to TIFF PackBits)
4 -- Fax (PSL2 PDF1.0 CCITTFaxEncode filter, Uncompressed=true!, K=-1,0,1,
EndOfLine=false, EncodedByteAlign=false, Columns=..., Rows=0,
EndOfBlock=true, BlackIs1=false, DamagedRowsBeforeError=0)
5 -- DCT (PSL2 PDF1.0 DCTEncode, options in JPEG stream)
6 -- IJG (PSL2 PDF1.0 DCTEncode, options in JPEG stream; the IJG libjpeg
library is used for compression, respecting the quality value 0..100)
7 -- JAI (PSL2 PDF1.0 DCTEncode, options in JPEG stream; JPEG-as-is: the
input file must be a JPEG file -- its contents are transferred
unmodified into the /DCTDecode JPEG stream)
-- TransferEncoding: enum
0 -- Binary (RawBits, see pbm(5), pgm(5), ppm(5))
1 -- ASCII (text, chars: 9,10,13,32..126)
2 -- Hex ((PSL1), PDF1.0, PSL2 ASCIIHexEncode filter)
3 -- 85 (PSL2 PDF1.0, ASCII85Encode filter)
4 -- base64, _not_ implemented
5 -- quoted-printable, _not_ implemented
6 -- URLencode, _not_ implemented
RGB -> Gray
"""""""""""
gray = 0.299*red + 0.587*green + 0.114*blue (NTSC video std)
gray = (306.176*red + 601.088*green + 116.736*blue) >> 10
perl -e 'no integer;for(@ARGV){y/#//d;$N=hex($_);$R=0.299*($N>>16)+0.587*(($N>>8)&255)+0.114*($N&255);print $R/255," ",sprintf("#%02x",int($R+0.5)),"\n"}' '#0f0f0f'
Rgb2 -> Gray
""""""""""""
perl -e 'no integer;for(@ARGV){print"$_
";y/#//d;$N=hex($_);$R=0.299*($N>>16)+0.587*(($N>>8)&255)+0.114*($N&255);
print "",$R/255," ",sprintf("#%02x",int($R+0.5)),"\n"}' 000000 000055 0000aa
0000ff 005500 005555 0055aa 0055ff 00aa00 00aa55 00aaaa 00aaff 00ff00
00ff55 00ffaa 00ffff 550000 550055 5500aa 5500ff 555500 555555 5555aa
5555ff 55aa00 55aa55 55aaaa 55aaff 55ff00 55ff55 55ffaa 55ffff aa0000
aa0055 aa00aa aa00ff aa5500 aa5555 aa55aa aa55ff aaaa00 aaaa55 aaaaaa
aaaaff aaff00 aaff55 aaffaa aaffff ff0000 ff0055 ff00aa ff00ff ff5500
ff5555 ff55aa ff55ff ffaa00 ffaa55 ffaaaa ffaaff ffff00 ffff55 ffffaa
ffffff
000000 0 #00
000055 0.038 #0a
0000aa 0.076 #13
0000ff 0.114 #1d
005500 0.195666666666667 #32
005555 0.233666666666667 #3c
0055aa 0.271666666666667 #45
0055ff 0.309666666666667 #4f
00aa00 0.391333333333333 #64
00aa55 0.429333333333333 #6d
00aaaa 0.467333333333333 #77
00aaff 0.505333333333333 #81
00ff00 0.587 #96
00ff55 0.625 #9f
00ffaa 0.663 #a9
00ffff 0.701 #b3
550000 0.0996666666666667 #19
550055 0.137666666666667 #23
5500aa 0.175666666666667 #2d
5500ff 0.213666666666667 #36
555500 0.295333333333333 #4b
555555 0.333333333333333 #55
5555aa 0.371333333333333 #5f
5555ff 0.409333333333333 #68
55aa00 0.491 #7d
55aa55 0.529 #87
55aaaa 0.567 #91
55aaff 0.605 #9a
55ff00 0.686666666666667 #af
55ff55 0.724666666666667 #b9
55ffaa 0.762666666666667 #c2
55ffff 0.800666666666667 #cc
aa0000 0.199333333333333 #33
aa0055 0.237333333333333 #3d
aa00aa 0.275333333333333 #46
aa00ff 0.313333333333333 #50
aa5500 0.395 #65
aa5555 0.433 #6e
aa55aa 0.471 #78
aa55ff 0.509 #82
aaaa00 0.590666666666667 #97
aaaa55 0.628666666666667 #a0
aaaaaa 0.666666666666667 #aa
aaaaff 0.704666666666667 #b4
aaff00 0.786333333333333 #c9
aaff55 0.824333333333333 #d2
aaffaa 0.862333333333333 #dc
aaffff 0.900333333333333 #e6
ff0000 0.299 #4c
ff0055 0.337 #56
ff00aa 0.375 #60
ff00ff 0.413 #69
ff5500 0.494666666666667 #7e
ff5555 0.532666666666667 #88
ff55aa 0.570666666666667 #92
ff55ff 0.608666666666667 #9b
ffaa00 0.690333333333333 #b0
ffaa55 0.728333333333333 #ba
ffaaaa 0.766333333333333 #c3
ffaaff 0.804333333333333 #cd
ffff00 0.886 #e2
ffff55 0.924 #ec
ffffaa 0.962 #f5
ffffff 1 #ff
Building the palette for Paletted image -> PSLC colorimage
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
{ Buf3 0 0 currentfile Bufx readstring pop
% /i 0 def
% Stack: Buf3 0 0 Bufx
{ % Stack: Buf3 <Buf3-dst-i> <0-1-2> <byte-read>
exch
{ { % Stack: Buf3 <Buf3-dst-i> <byte-read>
dup -2 bitshift Pal exch get
% Stack: Buf3 <Buf3-dst-i> <byte-read> <byte-to-write>
exch 4 bitshift /Carry exch def
% Stack: Buf3 <Buf3-dst-i> <byte-to-write>
3 copy put pop 1 add 1
% Stack: Buf3 <Buf3-dst-i+1> 1
}{dup -4 bitshift Carry add Pal exch get
exch 15 and 2 bitshift /Carry exch def
3 copy put pop 1 add 2
}{dup -6 bitshift Carry add Pal exch get
% Stack: Buf3 <Buf3-dst-i> <byte-read> <byte-to-write-first>
exch 4 copy
% Stack: Buf3 <Buf3-dst-i> <byte-to-write-first> <byte-read> Buf3 <Buf3-dst-i> <byte-to-write-first> <byte-read>
pop put
% Stack: Buf3 <Buf3-dst-i> <byte-to-write-first> <byte-read>
63 and Pal exch get pop
% Stack: Buf3 <Buf3-dst-i> <byte-to-write-second>
exch 1 add exch
3 copy put pop 1 add 0
% Stack: Buf3 <Buf3-dst-i+2> 0
}
} exch
% Stack: Buf3 <Buf3-dst-i> <byte-read> {code3} <0-1-2>
get exec
% Stack: Buf3 <Buf3-dst-i++> <1-2-0>
} forall
% Stack: Buf3 <i>
pop pop
Bufr
}
Color space conversion: (unfinished)
""""""""""""""""""""""""""""""""""""
-- Ripped from jccolor.c from libjpeg:
* YCbCr is defined per CCIR 601-1, except that Cb and Cr are
* normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
* The conversion equations to be implemented are therefore
* Y = 0.29900 * R + 0.58700 * G + 0.11400 * B
* Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE
* Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE
* (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
-- RGB -> YCbCr:
Y = 0.29900 * R + 0.58700 * G + 0.11400 * B
Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE
Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE
-- CMYK -> YCCK:
R=1-C, G=1-M, B=1-Y, K=K, RGB -> YCbCr
-- YCbCr -> RGB: (Cb < CENTERJSAMPLE, Cr < CENTERJSAMPLE)
R = Y + 1.40200 * Cr
G = Y - 0.34414 * Cb - 0.71414 * Cr
B = Y + 1.77200 * Cb
-- YCCK -> CMYK:
YCbCr -> RGB, C=1-R, M=1-G, Y=1-B, K=K.
-- (YCbCrK == YCCK)
-- Gray -> RGB: red = gray, green = gray, blue = gray
-- RGB -> Gray: gray = 0.299*red + 0.587*green + 0.114*blue (NTSC video std)
: gray = (306.176*red + 601.088*green + 116.736*blue) >> 10
: gray = (19595.264*red + 38469.632*green + 7471.104*blue) >> 16
-- Obsolete: RGB -> YCbCr: (YCbCr == YUV)
y:luminance = 0.299*red + 0.587*green + 0.114*blue (0..1)
cb:chrominance-b = blue - y = - 0.299*red - 0.587*green + 0.886*blue (-0.886 .. 0.886)
cr:chrominance-r = red - y = 0.701*red - 0.587*green - 0.114*blue (-0.701 .. 0.701)
Chrominance components can be represented less accurately since the
human eye is around twice as sensitive to luminance as to chrominance.
-- RGB <-> HSB: quite obfuscated. See gshsb.c in Aladdin Ghostscript's
source.
Word frequency counting in PostScript source
""""""""""""""""""""""""""""""""""""""""""""
perl -e '$C=0; $X=join"",<STDIN>; for (split" ",$X) { print "$_.\n";
$C+=length($_)-1 if /[0-9]/ }; print STDERR "C=$C\n"'
</tmp/t perl -e '$C=0; $X=join"",<STDIN>; $X=~s@([{}])@ $1 @g; $X=~s@/@ /@g;
for (split" ",$X) { print "$_.\n" if length>=2; $C++ if length($_)>=2 };
print STDERR "C=$C\n"' | sort | uniq
</tmp/t perl -e '$C=0; $X=join"",<STDIN>; $X=~s@([{}])@ $1 @g; $X=~s@/@ /@g;
$Y=""; for (split" ",$X) { $_=" $_ " if length($_)>=2; $Y.=$_ }; $Y=~s@
/@/@g; print $Y' >t
How tiff2ps displays a gray version of a PSLC Rgb8 image on PSL1
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
gsave
100 dict begin
1495.000000 935.000000 scale
/bwproc {
rgbproc
dup length 3 idiv string 0 3 0
5 -1 roll {
add 2 1 roll 1 sub dup 0 eq {
pop 3 idiv
3 -1 roll
dup 4 -1 roll
dup 3 1 roll
5 -1 roll put
1 add 3 0
} { 2 1 roll } ifelse
} forall
pop pop pop
} def
/colorimage where {pop} {
/colorimage {pop pop /rgbproc exch def {bwproc} image} bind def
} ifelse
%ImageData: 1495 935 8 3 0 1 2 "false 3 colorimage"
/line 4485 string def
1495 935 8
[1495 0 0 -935 0 935]
{currentfile line readhexstring pop} bind
false 3 colorimage
pts_defl.c which function calls which function
""""""""""""""""""""""""""""""""""""""""""""""
send_bits
rengeteg
flush_outbuf
send_bits
flush_block 2*
build_tree
flush_block 3*
flush_block
deflate2 5*
ct_tally
deflate2 sok*
longest_match
deflate2 2*
fill_window
deflate2 4*
gen_codes
2, reentrant
deflate2
1..
pts_deflate_init
1