[Tikzdevice-bugs] metapost device: problem with calculating font space?

[Charlie Sharpsteen]

   - On Mon, Apr 25, 2011 at 10:24 AM, mat <matthieu.stigler at gmail.com>wrote:

 Le 22. 04. 11 21:59, Charlie Sharpsteen a écrit :
>
sorry, it's just a stupid error from me: I run usually R CMD INSTALL, and
> tried this instead of make install!!  Once this used (after however a few
> tricks changing chown and chmod on the R created files) it works!!! Indeed,
> plots are much better now, and space better organized, thanks!!!!!
>

Glad it helped!



>
> I tried to adapt the metap function for my own needs (define a single spot
> colors and then its "childs") but got confused, as the script you wrote is
> quite complex!!! Idea is:
> -define.metap.color should just define generic spot color, no real color
> will be associated to it. Would format just
>
> \definecolor[PantoneBlue][c=1, m=0.58,y=0,k=0.29]
>
> -define.metap.tint should define the real colors used, which are just tints
> (%) of the defined spot colors. Would defined just:
>
> \definespotcolor[PantoneBlueSixtySpot][PantoneBlue][p=0.6,e=Pantone 294 C]
>
>
> See: metap_tint <- function(color_name, color_ref, p=1) {
>   # color_name: A name for the color. Should only contain letters.
>   # color_ref: The spot color it is based on
>   # p: the "tint" associated
>   if ( grepl('[^a-zA-Z]', color_name) ) {
>     stop("MetaPost color names cannot contain any characters other than
> ASCII letters!")
>   }
>
>   if(!color_ref%in%sapply(getOption('metapColors'), function(x)
> x$color_name)){
>     stop("color_ref not defined!")
>   } else {
>     color_ref_detail <-
> getOption('metapColors')[sapply(getOption('metapColors'), function(x)
> x$color_name)==color_ref][[1]]
>   }
>
>   return(
>     structure(
>       list(color_name = color_name, color_ref=color_ref, spot_name =
> color_ref_detail$spot_name, p=p),
>       class = 'metap_tint'
>     )
>   )
>
> }
>
>
> and its format counterpart:
>
> format.metap_tint <- function(color, ...) {
>   # Generates ConTeXt code for defining colors and spot colors.
>    color_def <- c(
>       "\n\\definespotcolor\n\t",
>       paste("[", color$color_name, "]\n\t", sep = ''),
>       paste("[", color$color_ref, "]\n\t", sep = ''),
>       paste("[p=", color$p, ", e=", color$spot_name, "]\n\t", sep =
> '')#      sprintf("[p=1,e=%s]\n", color$spot_name)
>     )
>
>   return( color_def )
> #  list(color_name = color_name, spot_name = color_ref_detail$spot_name,
> p=p),
> #       class = 'metap_tint'
> }
>
>
> But then I got confused where each color should be defined and exported :-(
> Any clear idea on how I should proceed?
>
> Thanks!!
>
> Matthieu
>

The problem with adding tint is that we have to pay attention to the
information received by the C-level routines of the device which is all we
have available to search the list of user defined colors for a matching
name.  What the C code receives is documented in the R Internals manual:

http://cran.r-project.org/doc/manuals/R-ints.html#Colours

We get four pieces of information--- R, G, B and Alpha (which is used to
denote transparency).  Adding tint would require a fifth piece
of information to be sent to the C routines which at the moment does not
appear to be possible unless the R graphics engine was re-written to support
alternative color models that could contain more information than RGBA.

An alternative would be to re-purpose the Alpha channel to denote tint
instead of transparency.  Then we would be able to map the A component of
RGBA to tint, but we would loose the ability to specify transparency. If you
were willing to make this tradeoff, then I think the following would need to
happen:

In metapColors.R:

   - col2rgb would need to be called with `alpha=TRUE` so that the alpha
   information is stored in rgb_value vectors.
   - format.metap_color would need to set `p` according to the new alpha
   component, rgb_value[4]. Divide it by 255 to get a percentage.
   - rgb2col would need to be modified to store alpha as well by adding it
   into the `rgb` call.

In metapDevice.c:

   - In MetaP_DrawStyle the else statement of the check on R_OPAQUE (line
   1442) should be eliminated.
   - MetaP_GetColorName will have to be modified to pass a vector of RBGA
   instead of just RGB to get_or_set_color in metapColors.R (line 1579).

Plus squashing the odd bug that will pop up :)

-Charlie