MS EMF (Enhanced Metafile) to SVG conversion library.

By themselves, EMF/EMF+ files are rare in the wild. However, they are frequently embedded inside other MS file formats.

This project was started to properly convert Visio stencils (.VSS) to svg and be able to reuse public stencils in other environments than MS Visio (see libvisio2svg).

However this project could be use beyond its original motivations to handle emf blobs in any MS formats.

• libiconv
• libpng
• libfontconfig
• libfreetype
• fmem (https://github.com/tamatebako/fmem) -- a cross-platform library for opening memory-backed libc streams
• argp-standalone (https://github.com/tom42/argp-standalone) -- a standalone version of the argp argument parsing functions from glibc, Windows only

fmem and argp-standalone libraries are integrated as CMake external projects. No additional installation or handling is required.

Installing the dependencies on Debian:

# compiler
apt-get install gcc g++
# or
apt-get install clang

# build deps
apt-get install cmake pkg-config

# library deps with their headers
apt-get install libpng-dev libc6-dev libfontconfig1-dev libfreetype6-dev zlib1g-dev

Installing the dependencies on macOS:

$ brew install argp-standalone cmake libpng freetype fontconfig gcc

Installing the dependencies on RHEL/CentOS/Fedora:

yum install cmake libpng-devel freetype-devel fontconfig-devel gcc-c++ gcc

Installing the dependencies on Windows for MSVC native builds Dependencies are installed by vcpkg package manager. Installation is implemented as a step of CMake configuration procedure.

Also note that in some rare cases, to properly handle text fields (ETO_GLYPH_INDEX flag), the ttf font used by the documents must be present and indexed (fontconfig) on your system.

Commands to build this project:

# options:
# * [-DUSE_CLANG=on]: use clang instead of gcc
# * [-DSTATIC=on]: build static library
# * [-DDEBUG=on]: compile with debugging symbols
# * [-DLONLY=on]: build the library only, no demo/test apps
#
# CMAKE_INSTALL_PREFIX is optional, default is /usr/local/

# Linux, MacOS
$ cmake . -DCMAKE_INSTALL_PREFIX=/usr/

# Windows native (MSVC) build
$ cmake . -DCMAKE_TOOLCHAIN_FILE=$(pwd)/vcpkg/scripts/buildsystems/vcpkg.cmake

# Cross-compilation
# This project employs vcpkg (https://github.com/microsoft/vcpkg) to setup cross-compilation environment
$ cmake . -DCMAKE_TOOLCHAIN_FILE=$(pwd)/vcpkg/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=<triplet>
# The following triplets are tested in CI:
# * x64-linux   (both for Ubuntu and ALpine Linux)
# * arm64-linux (Ubuntu)
# * x64-osx
# * arm64-osx
# * x64-mingw-static

# compilation
$ make

# installation
$ make install

Please note that you cannot use relative pathes when CMAKE_TOOLCHAIN_FILE is specified at cmake command line. You may need to replace $(pwd) with a reference that is appropriate for your environment.

$ ./emf2svg-conv --help
Usage: emf2svg-conv [OPTION...] -i FILE -o FILE
emf2svg -- Enhanced Metafile to SVG converter

  -h, --height=HEIGHT        Max height in px
  -i, --input=FILE           Input EMF file
  -o, --output=FILE          Output SVG file
  -p, --emfplus              Handle EMF+ records
  -v, --verbose              Produce verbose output
  -w, --width=WIDTH          Max width in px
  -?, --help                 Give this help list
      --usage                Give a short usage message
      --version              Print program version
  -V, --version              Print emf2svg version

Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.

Report bugs to https://github.com/kakwa/libemf2svg/issues.

# usage example:
$ ./emf2svg-conv -i ./tests/resources/emf/test-037.emf -o example.svg -v

Shorten examples:

Conversion from EMF to SVG (complete example here):

#include <emf2svg.h>
//[...]
int main(int argc, char *argv[]){

    /* emf content size */
    size_t emf_size;
    /* emf content */
    char * emf_content;
    /* svg output string */
    char *svg_out = NULL;
    /* svg output length */
    size_t svg_out_len = 0;

    //[...]

    /*************************** options settings **************************/

    /* allocate the options structure) */
    generatorOptions *options = (generatorOptions *)calloc(1, \
            sizeof(generatorOptions));
    /* debugging flag (prints the emf record in stdout if true) */
    options->verbose = true;
    /* emf+ flag (handles emf+ records if true) */
    options->emfplus = true;
    /* if a custom xml/svg namespace is needed (keep empty in doubt) */
    options->nameSpace = (char *)"svg";
    /* includes the svg start and stop tags (set to false if the result
     * of this call is meant to be used inside another svg) */
    options->svgDelimiter = true;
    /* image width in px (set to 0 to use the original emf device width) */
    options->imgWidth = 0;
    /* image height in px (set to 0 to use the original emf device height) */
    options->imgHeight = 0;

    /***************************** conversion ******************************/

    int ret = emf2svg(emf_content, emf_size, &svg_out, &svg_out_len, options);

    /***********************************************************************/

    //[...]
}

Check document for EMF+ record presence (complete example here):

int main(int argc, char *argv[]){

    /* emf content size */
    size_t emf_size;
    /* emf content */
    char * emf_content;
    /* svg output string */
    char *svg_out = NULL;
    /* svg output length */
    size_t svg_out_len = 0;

    bool emfplus;
    int ret = emf2svg_is_emfplus(emf_content, emf_size, &emfplus);
    if(emfplus)
        fprintf(stdout,"%s contains EMF+ records\n", file_name);
}

See ./src/conv/emf2svg.cpp for a real life example.

EMF RECORDS:

EMF+ RECORDS:

1.7.3:

• Fixed incorrect handling of polygon fill modes

1.7.2:

• vcpkg and GHA scripts update

1.7.1:

• added width and heigt attributes for svg even when Y-coordinates are repaired

1.7.0:

• refactor build scripts to facilitate better portability and ruby integration

1.6.0:

• add arm64 MacOS support (cross-compilation only, no tests)

1.5.0:

• add Alpine Linux support

1.4.0:

• add arm64 Debian Linux support (cross-compilation only, no tests)

1.3.1:

• add MSVC 17 (2022) support

1.3.0:

• add MSVC Windows native build

1.X.X: (forked to metanorma)

• add support for EMF images without an initial viewport setup
• add handling of EMF images with wrong transformation applied (Wine-generated)

1.1.0:

• add handling of font index encoding
• add fontconfig dependency
• add freetype dependency
• add common variables LIB_INSTALL_DIR, BIN_INSTALL_DIR, INCLUDE_INSTALL_DIR to set install directories

1.0.3:

• Fixing compilation on CentOS 7 (work around argp bug)

1.0.2:

• broken release, please don't use

1.0.1:

• cleaner handling of memstream on OSX (don't install libmemstream, just embed it)

1.0.0:

• better cmake regarding finding dependency libraries (libpng)
• /!\ API break, must pass an additionnal argument to emf2svg function:

--- a/goodies/old.c
+++ b/goodies/new.c
@@ -22,6 +22,8 @@ int main(int argc, char *argv[]){
     char * emf_content = mmap(0, emf_size, PROT_READ, MAP_PRIVATE, fd, 0);
     /* svg output string */
     char *svg_out = NULL;
+    /* svg output length */
+    size_t svg_out_len;

     /*************************** options settings **************************/

@@ -44,7 +46,7 @@ int main(int argc, char *argv[]){

     /***************************** conversion ******************************/

-    int ret = emf2svg(emf_content, emf_size, &svg_out, options);
+    int ret = emf2svg(emf_content, emf_size, &svg_out, &svg_out_len, options);

     /***********************************************************************/

• general cleanup of the project (remove external files not needed)

0.5.1:

• fix build on OS X

0.5.0:

• add alpha layer handling in bitmap blobs conversion
• add brush patterns

0.4.0:

• fix text orientation
• fix origin handling in special case

0.3.0:

• completly rework how the origin is calculated, it now takes correctly into account both viewport and window orgs

0.2.0:

• code reorganization
• add support for ANGLEARC, EMRSTRETCHBLT, EMRBITBLT and more
• add handling of bitmap, RLE4 and RLE8 image blobs
• add some rough handling of clipping forms
• fix text rendering to not collapse spaces

0.1.0:

• first version

General source code organisation:

• ./src/lib/emf2svg.c: API entry point.
• ./src/lib/emf2svg_rec_*: EMF record handlers
• ./src/lib/emf2svg_print.c: EMF record printer (debugging).
• ./src/lib/pmf2svg.c: EMF+ record handler.
• ./src/lib/pmf2svg_print.c: EMF+ record printer (debugging).
• ./src/conv/emf2svg.cpp: Command line tool.
• ./deps: external dependencies.

Useful links:

• MS-EMF: EMF specifications.
• MS-EMF+: EMF+ specifications.
• MS-WMF: WMF specifications.
• GDI: GDI specification (clearer than EMF in explaining how it works).
• SVG: SVG specifications.

• Stats on the number of emf records covered:

$ ./tests/resources/coverage.sh

• Fuzzing on the library:

Using American Fuzzy Lop:

# remove big files from test pool
$ mkdir ./tmp
$ find tests/resources/emf -size +1M -name "*.emf" -exec mv {} ./tmp \;

# compile with afl compiler
$ cmake -DCMAKE_CXX_COMPILER=afl-clang++ -DCMAKE_C_COMPILER=afl-clang .
$ make

# run afl (see man for more advanced usage)
$ afl-fuzz -i tests/resources/emf -o out/ -t 10000 -- ./emf2svg-conv -i '@@' -o out/

# restore the files
mv ./tmp/* tests/resources/emf

• Check correctness and memory leaks (xmllint and valgrind needed):

# options: -n to disable valgrind tests, -v for verbose output
# see -h for complete list of options
$ ./tests/resources/check_correctness.sh #[-n] [-v]

# generated svg:
$ ls tests/out/test-*
tests/out/test-000.emf.svg  tests/out/test-051.emf.svg
[...]

The emf files used for these checks are located in ./tests/resources/emf/.

To build, run on emf test files and visualize (with geeqie):

$ cmake .&& \
    make &&\
    "./tests/resources/check_correctness.sh" -n &&\
    geeqie "tests/out"

To check against corrupted emf:

$ cmake -DDEBUG=ON . &&\
    make &&\
    "./tests/resources/check_correctness.sh" -sxN \
    -e "./tests/resources/emf-corrupted/"

To print records index in svg as comments:

$ cmake -DINDEX=ON . && make

To reformat/reindent the code (clang-format):

$ ./goodies/format

In EMF coordinates are specified using an origin ([0,0] point) located at the upper-left corner: x-coordinates increase to the right; y-coordinates increase from top to bottom.

The SVG coordinate system, on the other hand, uses the same origin ([0,0] point) at the bottom-left corner: x-coordinates increase to the right; but y-coordinates increase from top to bottom.

Typically, a simple shift of the y-axis through a single SVG/CSS transformation is used to transform from EMF coordinates to SVG coordinates.

However, under certain circumstances some tools (for instance, SparxSystem Enterprise Architect in Wine) will generate EMF files with malformed coordinates. These images have an origin at the top-left corner with y-coordinates increasing from top to bottom, yet these y-coordinates are inverted (multiplied by -1) to simulate a normal EMF look.

Furthermore, this inversion phenomenon cannot be solved with plain mirroring as it occurs to all (complex) objects of the hierarchy. For example, text boxes have only their y-coordinate anchor point mirrored, but the text direction is set properly.

This specific layout issue cannot be fixed by a single SVG/CSS transformation, and therefore the processing code is required to detect and invert only the affected y-coordinates, while keeping other attributes intact.

Contribution are welcomed. Nothing special here, it's the usual "fork; commit(s); pull request". Only one thing however, run ./goodies/format (clang-format) before the pull request.