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Hints for graphics conversion, gxhconvert script

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Gnuplot to JPEG

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Gnuplot to JPEG

This page shows how to convert a Gnuplot file named x.gp into a JPEG image.

Are you sure you want to convert to JPEG?
PNG normally would be the better choice.

When converting vector graphics (like Gnuplot) to bitmap images (like JPEG) you have to specify a resolution. This is the number of pixels per inch.

When creating JPEG files a quality parameter is required for the compromise between file size and image quality.

Typically the value is in the range 80...95.

Values below 25 and above 98 are not recommended.

Prepare Gnuplot file for the gxhconvert script

No terminal, no output file name
Do not use
```
set terminal ...
set output ...
```
in Gnuplot files you want to use with gxhconvert.
Terminal type and output file name are provided by the gxhconvert script and passed as command line arguments to Gnuplot.
Optionally: Diagram width and height in special comments
Special comments have two raute characters (`#') at the start of line, example:
```
##  width   =   10cm
##  height  =   10cm
set xrange [0:10]
plot x*x title "\\(y=x^2\\)"
```
The gxhconvert script uses the tikz terminal instead of the usual cairolatex pdf terminal if width and height are specified. Make sure you have installed the "gnuplot-lua-tikz" package for LaTeX.
Optionally: Terminal type and setup in special comments
Example:
```
##  terminal    =   tikz
##  terminal setup  =   solid
```
For the terminal you can choose either "tikz" or "cairolatex".
Two backslashes in Gnuplot file for each LaTeX backslash
Gnuplot uses the backslash to escape some characters. So for each backslash you want to pass to LaTeX, write a sequence of two backslashes in the Gnuplot file.
Example:
```
set xlabel "\\(\\frac{x}{x_0}\\rightarrow\\)"
set ylabel "\\(\\overset{\\uparrow\\vspace{0.3em}}{y}\\)" rotate by 0
```
Note: The \overset instruction requires a line
```
preamble line = \usepackage{amsmath}
```
in the gxhconvert.conf file in the current working directory.

Choice 1: Use gxhconvert

Procedure

gxhconvert -o=jpg -r=_resolution_ -q=_quality_ x.gp

See the [gxhconvert manual] for a full description of the gxhconvert script.

Options

Option	Purpose
--pgf	Use PGF instructions in the intermediate .tex file instead of including a .pdf file.
--interlaced --jpeg‑progressive	Create progressive JPEG. The start of the file (data stream) allows to render the image in low quality, details for better quality follow.
--optimized --jpeg‑optimize	Optimize (decrease) file size. Computation takes a little longer and uses more memory.
--web	Shortcut for "--interlaced --optimized ".

Choice 2: Manual conversion, use PDF support file

Procedure

gnuplot -e "set terminal cairolatex pdf standalone ; set output 'x.tex'" x.gp
pdflatex -interaction=nonstopmode x
pdftoppm -r _resolution_ x.pdf | pnmtojpeg -quality=_quality_ > x.jpg

Temporary files

x.tex
x-inc.pdf
x.log
x.aux
x.pdf

Choice 3: Manual conversion, use PGF instructions

Procedure

gnuplot -e "set terminal tikz standalone plotsize 10cm,7cm ; set output 'x.tex'" x.gp
pdflatex -interaction=nonstopmode x
pdftoppm -r _resolution_ x.pdf | pnmtojpeg -quality=_quality_ > x.jpg