XForms: Problems drawing into a canvas

From: brandym@sbox.tu-graz.ac.at
Date: Wed Feb 02 2000 - 09:06:33 EST

  • Next message: T.C. Zhao: "Re: XForms: Problems drawing into a canvas"

    # To subscribers of the xforms list from brandym@sbox.tu-graz.ac.at :

    Hi !

    I experienced some strange behaviour in xforms 0.89 using flimage_display().

    I try to display an image which has been capture by a frame grabber
    using a canvas. Here's my source

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

      FL_IMAGE *myimage;
      unsigned char *image;

      // here's some init and
      // the allocation of image according to
      // the frame size of the grabber

    while(stay_in_this_loop)
     {
      image=grabimage(); // get a new frame

      if(!(myimage=flimage_alloc()))
        exit(-1);
        
      myimage->type=FL_IMAGE_GRAY;
      myimage->w=IMAGE_WIDTH;
      myimage->h=IMAGE_HEIGHT;
      flimage_getmem(myimage);
      
      for(row=0;row<IMAGE_HEIGHT;row++)
        for(col=0;col<IMAGE_WIDTH;col++)
          {
            myimage->gray[row][col]=(unsigned char)image[row*IMAGE_WIDTH+col];
          }
      
      if(flimage_sdisplay(myimage, FL_ObjWin(canvas))<0)
        exit(-2);
      
      flimage_free(myimage);
      

      do_some_gui_things();
    }
    /*********************************************************/

    This way it works once. I then tried to copy a new image from the
    grabber device into the (unsigned char *) image and wanted it
    to be displayed again - did NOT work !
    It seems to me as if a initialised FL_IMAGE structure can be displayed once,
    but if you do any changes to the gray-level data the changes can't
    be redisplayed.
    So what I'm doing no is to allocate/free the FL_IMAGE struct every time
    a new frame arrives from the grabber.
    Is there a faster/more efficient way to do this ? What am I doing wrong :(

    Thank you !

    Markus
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