Reading single MNG image failed

I use FLTK to show images. There exist CALLBACKS for stop, start, restart,
forward, backward, goto.

static void forward_cb(void)
{

     if(!play.handle)
    {
     return;
    }
     if(play.running)
    {
     return;
    }
     mng_retcode ret;
     mng_uint32 frame = mng_get_currentframe(play.handle);

     ret = mng_display_goframe(play.handle, frame);

     mng_display_freeze(play.handle);

}

MNG.cxx:183: forward_cb current_frame(2) delay(13)


flimage 1.13.1: error playing((null)) chunk[96]'MEND':
code(4099) severity(2) extra1(0) extra2(0)
text:'Framenr out of bounds'

//---------------

With APNG, 'forward_cb()' works:

static void forward_cb(void)
{
     if(aplay.running)
    {
     return;
    }
     FLImage_backward_activate(1);

     aplay.is_still_image = 1;

     next_frame();

     aplay.is_still_image = 0;

}//forward_cb()

static void next_frame()
{
     int i;

     if( !aplay.canvas) return;

     if((i = FLImage_frame_selected()) >= 0)
    {
     aplay.cur_frame = i;
    }
     i = aplay.cur_frame;

     if(i == aplay.num_frames)
    {
     i = 0;
    }

#ifdef _WIN32
     sprintf(aplay.end_of_path, "\\%d.png", i);
#else
     sprintf(aplay.end_of_path, "/%d.png", i);
#endif
     if(apng_buf)
    {
     free(apng_buf); apng_buf = NULL;
    }
    {
     FILE *reader;
     unsigned char *buf = (unsigned char*)calloc(1, aplay.rgb_size + 4);

     reader = fopen(aplay.rgb_path, "rb");

     fread(buf, 1, aplay.rgb_size, reader);
//-----------------------------------------------------------------------
     FLImage_use_buffer(buf, aplay.width, aplay.height, aplay.channels);
//-----------------------------------------------------------------------
     fclose(reader);

     apng_buf = buf;
    }
     FLImage_show_frame(i, aplay.num_frames-1);
     aplay.delay = apng_table[i].delay;
     aplay.cur_frame = i + 1;

     if(i == 0)
    {
     FLImage_backward_activate(0);
    }
     else
    {
     FLImage_backward_activate(1);
    }
//============================================================
     if(aplay.is_still_image) return;
//============================================================
     Fl::repeat_timeout(aplay.delay, wait_cb, aplay.rgb_path);

}//next_frame()

static void wait_cb(void *v)
{
     next_frame();
}

The APNG file has been dismantled into RGBA files:

root: ls /root/.png/

0.png 1.png etc.


Each of these files can be read: start_cb() , restart_cb() ;
or skipped: APNG_goto_frame(int i) ;
or shown as a single image: backward_cb, forward_cb


Q1: Is there no MNG function() to only read one image ?
Q2: Must I dismantle an MNG file into PNG RGBA files like in APNG ?

winfried




_______________________________________________
png-mng-implement mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/png-mng-implement