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Finished -process-images documentation

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John Whitington 2024-01-31 16:43:29 +00:00
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cpdfmanual.tex
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@ -3623,13 +3623,12 @@ The \texttt{-dump-attachments} operation, when given a PDF file and a directory
\vspace{1.5mm}
\noindent\small\verb!cpdf -process-images [-process-images-info] in.pdf [<range>]!\\
\noindent\small\verb! [-convert <filename>] [-jbig2enc <filename>]!\\
\noindent\small\verb! [-lossless-resample <n> | -lossless-to-jpeg <n>]!\\
\noindent\small\verb! [-lossless-resample[-dpi] <n> | -lossless-to-jpeg <n>]!\\
\noindent\small\verb! [-jpeg-to-jpeg <n>] [-1bpp-method <method>]!\\
\noindent\small\verb! [-jbig2-lossy-method <method>]!\\
\noindent\small\verb! [-jbig2-lossy-threshold <n>]!\\
\noindent\small\verb! [-pixel-threshold <n>] [-length-threshold <n>]!\\
\noindent\small\verb! [-percentage-threshold <n>] [-dpi-threshold <n>]!\\
\noindent\small\verb! [-resample-interpolate]!\\
\noindent\small\verb! [-dpi-target <n>]!\\
\noindent\small\verb! -o out.pdf!
@ -3794,7 +3793,7 @@ Option & Effect & Default value\\\hline
{\small\texttt{-pixel-threshold}} & Images below this number of pixels not processed & 25 \\
{\small\texttt{-length-threshold}} & Images with less than this number of bytes of data not processed & 100 \\
{\small\texttt{-percentage-threshold}} & Results not below this percentage of original size discarded & 99 \\
{\small\texttt{-dpi-threshold}} & Only images above this threshold at all use points processed & (no dpi check)\\\hline
{\small\texttt{-dpi-threshold}} & Only images above this threshold at all use points processed & (no dpi check)
\end{tabular}
\bigskip
@ -3811,10 +3810,24 @@ Option & Effect & Default value\\\hline
\noindent\small\verb!cpdf -process-images -lossless-resample-dpi 300 in.pdf -o out.pdf!
\end{framed}
\noindent The methods so far introduced do not operate on 1 bit per pixel data. Different compression mechanisms are typically in use, and we need a different approach.
\noindent The methods so far introduced do not operate on 1 bit per pixel data. Different compression mechanisms are typically in use, and we need a different approach. The \texttt{-1bpp-method} option specifies what to do with losslessly compressed 1 bit-per-pixel images.
%\noindent\small\verb! [-jbig2enc <filename>]!\\
%\noindent\small\verb! [-1bpp-method <method>] [-jbig2-lossy-method <method>]!\\
\bigskip
\begin{tabular}{lp{10cm}l}
Method & Effect\\\hline
{\small\texttt{JBIG2}} & Lossless JBIG2 \\
{\small\texttt{JBIG2Lossy}} & Lossy JBIG2, sharing JBIG2Globals data amongst all images.
\end{tabular}
\bigskip
\noindent These options require the \texttt{jbig2enc} program, whose location may be specified with \texttt{-jbig2enc}. For lossy JBIG2, the threshold for similarity of data may be set with \texttt{-jbig2-lossy-threshold}. For example:
\begin{framed}
\noindent\small\verb!cpdf -process-images -jbig2enc /usr/bin/jbig2enc -1bpp-method JBIG2Lossy!\\
\noindent\small\verb! -jbig2-lossy-threshold 75 in.pdf -o out.pdf!
\end{framed}
\noindent It is not currently possible to reprocess lossless JBIG2 into lossy JBIG2, nor is it possible to recompress into CCITT.
\begin{cpdflib}
\clearpage