Live Image from camera in GTK

Question

First:
I am working on a dark-field microscopic tracking program. This program is old (2012), we got a new camera but this camera can´t be captured with a capture program. So I need to write a "capture program" for this camera with the SDK (Software development kit) from the company of the camera.

The tracking program is writen in C and GTK 2, so I would like to have the "capture program" in C and GTK 2 too, so I can just put the "capture program" in my tracking program. I can take a picture inside the "capture program" and show it as gtk_image_new_from_pixbuf .

Problem:
After being able to take pictures I found out that the dark-field microscope is not able to let you set the focus for the camera with your eyes. So now I need to capture a "live image", video or how ever you want to call it.
My idea was to use a timer so the camera will take a picture every second and display it as an image so the program has to delete the old image and show the new one. But that doesn´t happen I am pretty sure that there is no problem with the camera, because it shows the first image. My guess is that the pixbuf isn´t cleared and that causes that there is no new image shown.
The "capture program" doesn´t have to stay as a C/Gtk2 program but as I am not a computer scientist I just have no idea how to get the images into the tracking program if they are different.

Code:
I know that gdk_pixbuf_new_from_data has a starde of width*1 and not width*3 that is no problem.

#include <gtk/gtk.h>
#include <stdlib.h>

unsigned short *buffer = NULL;
long imageSize = 0;

void draw_call (GtkWidget *window, GdkEvent *event, gpointer data){

    (void)event; (void)data;
    GdkPixbuf *pix;
    GtkWidget* image;
    image = gtk_image_new();

    free (buffer);
    long result = NOERR;


//camera commands had to be changed 
    result = getImageSizeFromCamera( &imageSize);

    result = SetBitsPerPixel(8);

    buffer = (unsigned short *) malloc( imageSize*2);

    result = takePicture(camera, buffer, imageSize/2, NULL, NULL);

    result = stopTakingPicture (camera);
//end of camera commands

    pix = gdk_pixbuf_new_from_data ((unsigned int *) buffer, GDK_COLORSPACE_RGB,FALSE, 8,
               1936, 1460, 1936*1, pixbuf_free, NULL);

    image = gtk_image_new_from_pixbuf(pix);


    return image;
gtk_widget_unref (pix);
}

void pixbuf_free(guchar *pixels, gpointer data)
{
    g_free(pixels) ;
    fprintf(stderr, "pixbuf data freed\n") ;
}

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

    GdkPixbuf *pixbuf;


    // GTK

    GtkWidget *window;
    GtkWidget* image;

    image = gtk_image_new();


    gtk_init (&argc, &argv);

    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);


    gtk_window_set_title (GTK_WINDOW (window), "Image Viewer");

    g_signal_connect (window, "destroy", G_CALLBACK (Deinit), NULL);
    g_signal_connect (window, "expose-event",G_CALLBACK (draw_call), NULL);


    g_timeout_add (1000, draw_call, NULL);

    gtk_widget_set_app_paintable(window, TRUE);
    gtk_widget_set_double_buffered(window, FALSE);


    gtk_container_add(GTK_CONTAINER (window), image);

    gtk_widget_show_all (window);

    gtk_main ();


    return 0;
}

Answer 1

The updating of the images is triggered by the expose_event callback that is draw_call in your code, for details see How to get webcam feed to GTK window?

You know that there is tracking implemented in OpenCV? https://docs.opencv.org/3.4/d2/d0a/tutorial_introduction_to_tracker.html

You can also code the image capturing in OpenCV

OpenCV - Getting picture from default webcam in C/C++ - GTK Issues

In GUVCVIEWER is implemented the functionality that you need and possibly you can port the source code if your camera uses the uvc driver https://github.com/jaswdr/guvcview/blob/master/gview_v4l2core/v4l2_core.c

Answer 2

You have multiple problems:

1. Your drawing function does not have correct signature to be used in g_timer_add . It must return a TRUE to keep going and it must take other parameters.

2. You have some code after returning from that function which can never bbe executed.

3. You return a pointer to GtkImage from timer handler wich is not correct. It must return TRUE/FALSE . The timer wrapper does not know what to do with such a pointer.

4. You do not update any widget yourself. I will show this in an example.

5. You create images again and again while you only need to update the existing one.

I have extended the sample for your previous question with update functionality:

// build:
// gcc -o test `pkg-config --cflags gtk+-3.0` -Wall -Wextra test.c `pkg-config --libs gtk+-3.0`


#include <stdlib.h>
#include <stdint.h>
#include <gtk/gtk.h>

typedef struct {
  uint8_t r;
  uint8_t g;
  uint8_t b;
} rgb;


int basecolour = 0;


void pixbuf_free(guchar *pixels, gpointer data)
{
  g_free(pixels) ;
  (void)data;    
  fprintf(stderr, "pixbuf data freed\n") ;
}

gboolean draw_call(gpointer user_data)
{
    GtkImage *image = (GtkImage *) user_data;
    
  size_t Width  = 1936;
  size_t Height = 1280;
  size_t Stride_rgb = Width; // Might need rounding up

  // Put raw image data from the camera in the buffer.     
  rgb *buffer_rgb = malloc(Stride_rgb * Height * sizeof(rgb));

  for (size_t x = 0; x < Width; x++)
    for (size_t y = 0; y < Height; y++)
    {
      // Convert 1 byte greyscale in 3 byte RGB:
      uint8_t grey = (basecolour + x+y) & 0xFF;
      buffer_rgb[Stride_rgb*y + x].r = grey;
      buffer_rgb[Stride_rgb*y + x].g = grey;
      buffer_rgb[Stride_rgb*y + x].b = grey;
    }
    basecolour += 5;

  GdkPixbuf *pixbuf_rgb = gdk_pixbuf_new_from_data((guchar*)buffer_rgb, GDK_COLORSPACE_RGB,FALSE, 8,
              Width, Height, Stride_rgb*3, pixbuf_free, NULL);
  gtk_image_set_from_pixbuf(image, pixbuf_rgb);
  g_object_unref(pixbuf_rgb);

  return TRUE;  
}

int main (int argc, char *argv[])
{
    size_t Width  = 1936;
    size_t Height = 1280;
    size_t Stride_8 = Width;   // Might need rounding up
    size_t Stride_rgb = Width; // Might need rounding up

    //Due to lack of camera data, lets use some dummy data...
    uint8_t *buffer_8 = malloc(Stride_8*Height);
    for (size_t x = 0; x < Width; x++)
      for (size_t y = 0; y < Height; y++)
        buffer_8[Stride_8*y + x] = (x+y) & 0xFF;

    /*code to take raw image data from camera*/

    // Put raw image data from the camera in the buffer.     
    rgb *buffer_rgb = malloc(Stride_rgb * Height * sizeof(rgb));

    for (size_t x = 0; x < Width; x++)
      for (size_t y = 0; y < Height; y++)
      {
        // Convert 1 byte greyscale in 3 byte RGB:
        uint8_t grey = buffer_8[Stride_8*y + x];
        buffer_rgb[Stride_rgb*y + x].r = grey;
        buffer_rgb[Stride_rgb*y + x].g = grey;
        buffer_rgb[Stride_rgb*y + x].b = grey;
        }

    // GTK
    gtk_init(&argc, &argv);
    GtkWidget *window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_title(GTK_WINDOW (window), "test");
    g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);

    GdkPixbuf *pixbuf_rgb = gdk_pixbuf_new_from_data((guchar*)buffer_rgb, GDK_COLORSPACE_RGB,FALSE, 8,
               Width, Height, Stride_rgb*3, pixbuf_free, NULL);
    GtkWidget *image = gtk_image_new_from_pixbuf(pixbuf_rgb);
    g_object_unref(pixbuf_rgb);  

    gtk_container_add(GTK_CONTAINER(window), image);
    gtk_widget_show_all(window);

    g_timeout_add (1000, draw_call, image);
    gtk_main();
    
    return 0;
}

Again, I have added some dummy code to replace your image capture part. I have tested on Linux and it updates the image with every call of the timer handler.