我在玩魔方和魔法...

library(magick); #install.packages("magick", dependencies=TRUE);
library(tesseract); # install.packages("tesseract");
# https://github.com/ropensci/magick/issues/154

img.file = "iris-ocr.png";

img = magick::image_read( img.file );
img.txt = tesseract::image_ocr(img);

cat(img.txt);

注意：img.file和运行代码的笔记本在同一个位置。也就是说，没有使用setwd（），也没有完整的文件路径。但是它工作了。为了尝试，下面是PNG图像文件：

https://raw.githubusercontent.com/MonteShaffer/MasterClassDataAnalytics/main/-course-/02.020_hello-world-notebook/iris-ocr.png

所以我深入研究了magick的源代码

rdx = readRDS("C:\\Users\\Monte J. Shaffer\\Documents\\R\\win-library\\4.1\\magick\\R\\magick.rdx");

info = rdx$variables$magick_image_readpath;

# # https://stackoverflow.com/questions/61841221/how-to-view-open-and-save-a-rdb-file-in-rstudio

readRDB <- function(filename, offset, size, type = 'gzip') {
        f <- file(filename, 'rb')
        on.exit(close(f))
        seek(f, offset + 4)
        unserialize(memDecompress(readBin(f, 'raw', size - 4), type))
}

obj = readRDB("C:\\Users\\Monte J. Shaffer\\Documents\\R\\win-library\\4.1\\magick\\R\\magick.rdb", offset=info[1], size=info[2]);

其显示如下：

function (paths, density, depth, strip, defines) 
{
    .Call("_magick_magick_image_readpath", PACKAGE = "magick", 
        paths, density, depth, strip, defines)
}

源Rcpp代码显示：

// magick_image_readpath
XPtrImage magick_image_readpath(Rcpp::CharacterVector paths, Rcpp::CharacterVector density, Rcpp::IntegerVector depth, bool strip, Rcpp::CharacterVector defines);
RcppExport SEXP _magick_magick_image_readpath(SEXP pathsSEXP, SEXP densitySEXP, SEXP depthSEXP, SEXP stripSEXP, SEXP definesSEXP) {
BEGIN_RCPP
    Rcpp::RObject rcpp_result_gen;
    Rcpp::RNGScope rcpp_rngScope_gen;
    Rcpp::traits::input_parameter< Rcpp::CharacterVector >::type paths(pathsSEXP);
    Rcpp::traits::input_parameter< Rcpp::CharacterVector >::type density(densitySEXP);
    Rcpp::traits::input_parameter< Rcpp::IntegerVector >::type depth(depthSEXP);
    Rcpp::traits::input_parameter< bool >::type strip(stripSEXP);
    Rcpp::traits::input_parameter< Rcpp::CharacterVector >::type defines(definesSEXP);
    rcpp_result_gen = Rcpp::wrap(magick_image_readpath(paths, density, depth, strip, defines));
    return rcpp_result_gen;
END_RCPP
}

我熟悉C++（和PHP）的__FILE__语法：https://www.tutorialspoint.com/what-are-file-line-and-function-in-cplusplus
使用R和Rcpp，如何为__FILE__编写宏或函数？
例如，

getFILE = function() { __FILE__; }

类似于：

Rcpp::cppFunction("long long RShift(long long a, int b) { return a >> b;}");
Rcpp::cppFunction("long long LShift(long long a, int b) { return a << b;}");

接下来的问题是，如何在安装软件包时启用这些功能？