Linux: libgphoto2 image capture from Canon EOS 1Ds Mark III

Here's the missing "hello, world" program for libgphoto2. I called it canon-capture, since I was working with Canon EOS SLR cameras, but it might actually work with anything supported by libgphoto2. Having to set-config capture=1 might be canon-specific, but the rest of the guts are pretty generic.

// compile with gcc -Wall -o canon-capture -lgphoto2 canon-capture.c
// This code released into the public domain 21 July 2008
//
// This program does the equivalent of:
// gphoto2 --shell
//   > set-config capture=1
//   > capture-image-and-download
// compile with gcc -Wall -o canon-capture -lgphoto2 canon-capture.c

#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <gphoto2/gphoto2.h>

void errordumper(GPLogLevel level, const char *domain, const char *format,
                 va_list args, void *data) {


  vfprintf(stdout, format, args);
  fprintf(stdout, "\n");
}

void enable_capture(Camera *canon, GPContext *canoncontext) {
  int retval;

  printf("Get root config.\n");
  CameraWidget *rootconfig; // okay, not really
  CameraWidget *actualrootconfig;

  retval = gp_camera_get_config(canon, &rootconfig, canoncontext);
  actualrootconfig = rootconfig;
  printf("  Retval: %d\n", retval);

  printf("Get main config.\n");
  CameraWidget *child;
  retval = gp_widget_get_child_by_name(rootconfig, "main", &child);
  printf("  Retval: %d\n", retval);

  printf("Get settings config.\n");
  rootconfig = child;
  retval = gp_widget_get_child_by_name(rootconfig, "settings", &child);
  printf("  Retval: %d\n", retval);

  printf("Get capture config.\n");
  rootconfig = child;
  retval = gp_widget_get_child_by_name(rootconfig, "capture", &child);
  printf("  Retval: %d\n", retval);


  CameraWidget *capture = child;

  const char *widgetinfo;
  gp_widget_get_name(capture, &widgetinfo);
  printf("config name: %s\n", widgetinfo );

  const char *widgetlabel;
  gp_widget_get_label(capture, &widgetlabel);
  printf("config label: %s\n", widgetlabel);

  int widgetid;
  gp_widget_get_id(capture, &widgetid);
  printf("config id: %d\n", widgetid);

  CameraWidgetType widgettype;
  gp_widget_get_type(capture, &widgettype);
  printf("config type: %d == %d \n", widgettype, GP_WIDGET_TOGGLE);


  printf("Set value.\n");

  int one=1;
  retval = gp_widget_set_value(capture, &one);
  printf("  Retval: %d\n", retval);

  printf("Enabling capture.\n");
  retval = gp_camera_set_config(canon, actualrootconfig, canoncontext);
  printf("  Retval: %d\n", retval);
}

/* This seems to have no effect on where images go
void set_capturetarget(Camera *canon, GPContext *canoncontext) {
  int retval;
  printf("Get root config.\n");
  CameraWidget *rootconfig; // okay, not really
  CameraWidget *actualrootconfig;

  retval = gp_camera_get_config(canon, &rootconfig, canoncontext);
  actualrootconfig = rootconfig;
  printf("  Retval: %d\n", retval);

  printf("Get main config.\n");
  CameraWidget *child;
  retval = gp_widget_get_child_by_name(rootconfig, "main", &child);
  printf("  Retval: %d\n", retval);

  printf("Get settings config.\n");
  rootconfig = child;
  retval = gp_widget_get_child_by_name(rootconfig, "settings", &child);
  printf("  Retval: %d\n", retval);

  printf("Get capturetarget.\n");
  rootconfig = child;
  retval = gp_widget_get_child_by_name(rootconfig, "capturetarget", &child);
  printf("  Retval: %d\n", retval);


  CameraWidget *capture = child;

  const char *widgetinfo;
  gp_widget_get_name(capture, &widgetinfo);
  printf("config name: %s\n", widgetinfo );

  const char *widgetlabel;
  gp_widget_get_label(capture, &widgetlabel);
  printf("config label: %s\n", widgetlabel);

  int widgetid;
  gp_widget_get_id(capture, &widgetid);
  printf("config id: %d\n", widgetid);

  CameraWidgetType widgettype;
  gp_widget_get_type(capture, &widgettype);
  printf("config type: %d == %d \n", widgettype, GP_WIDGET_RADIO);


  printf("Set value.\n");

  // capture to ram should be 0, although I think the filename also plays into
  // it
  int one=1;
  retval = gp_widget_set_value(capture, &one);
  printf("  Retval: %d\n", retval);

  printf("Enabling capture to CF.\n");
  retval = gp_camera_set_config(canon, actualrootconfig, canoncontext);
  printf("  Retval: %d\n", retval);
}
*/

void capture_to_file(Camera *canon, GPContext *canoncontext, char *fn) {
  int retval;

  printf("Capturing.\n");
  CameraFilePath camera_file_path;

  // NOP: This gets overridden in the library to /capt0000.jpg
  strcpy(camera_file_path.folder, "/");
  strcpy(camera_file_path.name, "foo.jpg");

  retval = gp_camera_capture(canon, GP_CAPTURE_IMAGE, &camera_file_path, canoncontext);
  printf("  Retval: %d\n", retval);

  printf("Pathname on the camera: %s/%s\n", camera_file_path.folder, camera_file_path.name);

  CameraFile *canonfile;

  retval = gp_file_new(&canonfile);
  printf("  Retval: %d\n", retval);
  retval = gp_camera_file_get(canon, camera_file_path.folder, camera_file_path.name,
                     GP_FILE_TYPE_NORMAL, canonfile, canoncontext);
  printf("  Retval: %d\n", retval);

  const char *filedata;
  unsigned long int filesize;

  retval = gp_file_get_data_and_size(canonfile, &filedata, &filesize);
  printf("  Retval: %d\n", retval);

  int fd = open(fn, O_CREAT | O_WRONLY, 0644);
  write(fd, filedata, filesize);
  close(fd);

  printf("Deleting.\n");
  retval = gp_camera_file_delete(canon, camera_file_path.folder, camera_file_path.name,
                        canoncontext);
  printf("  Retval: %d\n", retval);

  gp_file_free(canonfile);
}



main() {
  Camera *canon;

  gp_log_add_func(GP_LOG_ERROR, errordumper, NULL);
  GPContext *canoncontext = gp_context_new();
  gp_camera_new(&canon);

  // When I set GP_LOG_DEBUG instead of GP_LOG_ERROR above, I noticed that the
  // init function seems to traverse the entire filesystem on the camera.  This
  // is partly why it takes so long.
  printf("Camera init.  Takes about 10 seconds.\n");
  int retval = gp_camera_init(canon, canoncontext);
  printf("  Retval: %d\n", retval);

  enable_capture(canon, canoncontext);
  //set_capturetarget(canon, canoncontext);

  int i;
  capture_to_file(canon, canoncontext, "foo.jpg");

  gp_camera_exit(canon, canoncontext);
}