Missing documented key in graphicx user guide : decodearray #2009
Description
The file graphicx.pdf don't document the key decodearray of \includegraphics.
Pages 2, 3 and 4 speak about:
bb,bbllx,bblly,bburx,bbury,natwidth,natheight,viewport,trim,hiresbb,angle,origin,width,height,totalheight,keepaspectratio,scale,clip,draft,type,ext,read,command,quiet,page,interpolate,pagebo,alt,actualtext,artifact
but not about decodearray.
We can only see something on page 7:
but this don't provide any information for the final user (how to use it?)
I discover the decodearray key in some questions on tex.stackexchange.com.
For example at: https://tex.stackexchange.com/a/670097
But here the users say it take 6 numbers.
And at https://tex.stackexchange.com/a/150219/132405
I read a contradiction anwser (55 upvote) which say that decodearry takes 2 numbers...
If I try code (with pdflatex) like
\documentclass[11pt]{article}
\usepackage{graphicx}
\begin{document}
\includegraphics[scale=0.1,page=8,decodearray={0.8 1 0.8 1 0.8 1}]{example-image-a4-numbered.pdf} \includegraphics[scale=0.1,page=8,decodearray={0.8 1 -0.8 1 0.8 1}]{example-image-a4-numbered.pdf} \includegraphics[scale=0.1,page=8]{example-image-a4-numbered.pdf} No working with pdf?% nothing change with pdf
\includegraphics[scale=0.2,decodearray={0.8 1 0.8 1 0.8 1}]{example-image.png} Why isn't $[0,1] \to [0.8,1]$ (almost white output)?
\includegraphics[scale=0.2,decodearray={0.2 1 0.2 1 0.2 1}]{example-image.png} \includegraphics[scale=0.2]{example-image.png}
Output here (2 values):\includegraphics[scale=0.2,decodearray={0.2 1}]{example-image.png} % Yes, no error with only 2 values
\includegraphics[scale=0.2]{example-grid-100x100bp.jpg} \includegraphics[scale=0.2,decodearray={-0.8 1 0.8 1 0.8 1}]{example-grid-100x100bp.jpg}
No output here (2 values): \includegraphics[scale=0.2,decodearray={-0.8 1}]{example-grid-100x100bp.jpg} % no output with only 2 values
\end{document}
almost nothing is understood...
Based on https://tex.stackexchange.com/a/760101 (for (0..1) → (-1..1), 0.7 becomes 0.4) I have drawn this:
But it seems incorrect based on the code and the output shown above. So please add explanations in the documentation. Thanks.
And if decodearray isn't documented because perhaps comes frome the LaTex kernel or pdflatex driver, please explain where whe can find the information (and also if another keys aren't documented).
Thanks.