diff options
Diffstat (limited to 'doc/context/sources/general/manuals/workflows')
-rw-r--r-- | doc/context/sources/general/manuals/workflows/workflows-graphics.tex | 51 | ||||
-rw-r--r-- | doc/context/sources/general/manuals/workflows/workflows-mkiv.tex | 2 |
2 files changed, 49 insertions, 4 deletions
diff --git a/doc/context/sources/general/manuals/workflows/workflows-graphics.tex b/doc/context/sources/general/manuals/workflows/workflows-graphics.tex index 55a8ad701..2cff143f4 100644 --- a/doc/context/sources/general/manuals/workflows/workflows-graphics.tex +++ b/doc/context/sources/general/manuals/workflows/workflows-graphics.tex @@ -145,9 +145,54 @@ of special and only makes sense when you use the graphic database options. The and how conversion of images takes place. The \type {graphics.lognames} will make sure that some extra information about -used graphics is saved in the log file, while \type {graphics.usage} will produce -a file \typ {<jobname>-figures-usage.lua} that contains information about found -(or not found) images and the way they are used. +used graphics is saved in the log file, The \type {graphics.usage} tracker will +produce a file \typ {<jobname>-figures-usage.lua} that contains information about +found (or not found) images and the way they are used. + +\stopsection + +\startsection[title=Compression] + +A \PNG\ image uses several methods for compression. The image data itself can be +compacted by taking pixels around each individual pixel into account. Storing +deltas instead of absolute values can for instance result in strips of zeros. +These in turn compress well using zlib compression. Each scanline starts with a +filterbyte that indicates how to look at the surrounding pixels. While in \PDF\ a +\JPEG\ image is included as|-|is, a \PNG\ often take a bit more work. A +(optional) mask has to be split off, as does an (optional) index. In the worst +case we need to deinterlace. The \PNG\ inclusion mechanism in \CONTEXT\ \LMTX\ +takes care of this in an as efficient as possible way. Nevertheless there are +some knobs you can turn: + +\starttyping +\enabledirectives[graphics.png.recompress] +\enabledirectives[graphics.png.compresslevel=9] +\stoptyping + +A higher compress level makes the run somewhat smaller but also fives smaller +files. The default compress level is~3. When an image doesn't need to be +transformed (due to mask, index or interlace), you have to force recompression +with the \type {recompress} directive. The sample image \type {mill.png} has a +size of \type {154,869} bytes. + +\starttyping +\startTEXpage + \externalfigure[mill.png] +\stopTEXpage +\stoptyping + +The next table shows the consequences of setting the directives. The runtime is +of course dependent of the machine you run the sample on. If you have lots of +images it might make sense to have a final run with a higher compress level. The +\PDF\ file has some extra overhead (like metadata and page related information). + +\starttabulate[|l|c|c|c|] +\BC \BC compression \BC filesize \BC runtime \NC \NR +\BC default \NC \NC 156,964 \NC 0.516 \NC \NR +\BC recompress \NC 3 \NC 144,418 \NC 0.531 \NC \NR +\BC compresslevel \NC 0 \NC 281,071 \NC 0.516 \NC \NR +\BC compresslevel \NC 9 \NC 137,375 \NC 0.547 \NC \NR +\stoptabulate \stopsection diff --git a/doc/context/sources/general/manuals/workflows/workflows-mkiv.tex b/doc/context/sources/general/manuals/workflows/workflows-mkiv.tex index 52070c49e..a6d29ac42 100644 --- a/doc/context/sources/general/manuals/workflows/workflows-mkiv.tex +++ b/doc/context/sources/general/manuals/workflows/workflows-mkiv.tex @@ -15,7 +15,7 @@ % Group journal or otherwise. Thanks to the editors for corrections. Also thanks % to users for testing, feedback and corrections. -\setupbackend[export=yes] +% \setupbackend[export=yes] \environment workflows-style |