CGI QR-Code logo

The resulting QR-Code should look something like this:


It is generated dynamically from referer URL sent by the user agent.


To compile and run cqrlogo you need:

Additionally it is expected to have make and pkg-config around to successfully compile.

Some systems may require additional development packages for the libraries. Look for libpng-dev, libz-dev and libqrencode-dev or similar.

For make check to work you have to install optional dependency zbar.

Build and install

Building and installing is very easy. Just run:


followed by:

make install

This will place a shared library at /usr/lib/libcqrlogo.so, an executable at /usr/lib/cqrlogo/cqrlogo and documentation can be found in /usr/share/doc/cqrlogo/.

The file config.h (copy from config.def.h if it does not exist) provides some build time configuration, so feel free to make your changes there and rerun the commands above.

Static build

In case you do not like the shared library libcqrlogo.so for whatever reason you can build a statically linked version:

make static

However there is no install routine for the static build. Please note that this is still dynamically linked to libpng, libz, libiniparser and libqrencode.


This is a CGI executable (Common Gateway interface), so it is expected to be run inside a web server. Consult your web server's documentation to get information about how to run CGI executables.

By default cqrlogo generates a file with scale two, so one QR-Code pixel results in 2x2 pixels. The border is one pixel (though scale takes effect) and error correction level is the lowest available.

Runtime options can be given with request method GET. These are available:

  • scale: scale the QR-Code up by this factor
  • border: width of the border
  • level: error correction level


This now uses a shared library the can be used to create CGI executables for your custom needs. This is minimal sample source code:

#include <libcqrlogo.h>

int main(int argc, char **argv) {
        struct cqr_png * png;
        struct cqr_conf conf;

        conf.scale = 2;
        conf.border = 1;
        conf.level = 0;
        conf.overwrite = 1;

        /* generate PNG data */
        if ((png = cqr_encode_qrcode_to_png("https://github.com/eworm-de/cqrlogo", conf, CQR_META_ALL)) == NULL) {
                fprintf(stderr, "Failed to generate PNG.\n");
                return EXIT_FAILURE;

        /* print HTTP header */
        fputs(CQR_HEADER_CONTENT_TYPE, stdout);
        fputc('\n', stdout);

        /* write PNG data to stdout */
        if (fwrite(png->buffer, png->size, 1, stdout) != 1) {
                fprintf(stderr, "Failed writing PNG data to stdout.\n");
                return EXIT_FAILURE;

        /* free memory we no longer need */
        if (png->size > 0)

        return EXIT_SUCCESS;

Save this code to cqrlogo.c and run:

gcc -lcqrlogo -o cqrlogo.cgi cqrlogo.c

This will result in a CGI executable cqrlogo.cgi.


URL: GitHub.com

Mirror: eworm.de GitHub.com