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• How to save an SDL bitmap to memory and load it back ?

  19 novembre 2012, par Nav

  I have a bunch of RWops functions :

  static int myseekfunc(SDL_RWops *context, int offset, int whence) { SDL_SetError("Can't seek in this kind of RWops"); return(-1); }
  
  static int myreadfunc(SDL_RWops *context, void *ptr, int size, int maxnum) { memset(ptr,0,size*maxnum); return(maxnum); }
  
  static int mywritefunc(SDL_RWops *context, const void *ptr, int size, int num) { return(num); }
  
  static int myclosefunc(SDL_RWops *context) 
  
  { 
  
    if(context->type != 0xdeadbeef) { SDL_SetError("Wrong kind of RWops for myclosefunc()"); return(-1); }
  
    free(context->hidden.unknown.data1);
  
    SDL_FreeRW(context);
  
    return(0);
  
  }
  
  
  
  // Note that this function is NOT static -- we want it directly callable from other source files 
  
  SDL_RWops *MyCustomRWop()
  
  {
  
    SDL_RWops *c=SDL_AllocRW();
  
    if(c==NULL) return(NULL);
  
  
  
    c->seek =myseekfunc;
  
    c->read =myreadfunc;
  
    c->write=mywritefunc;
  
    c->close=myclosefunc;
  
    c->type =0xdeadbeef;
  
    printf("deadbeef=%d\n",c->type);
  
    c->hidden.unknown.data1=malloc(256);//IS THIS CORRECT?
  
    return(c);
  
  }

  with which I'm trying to write a BMP into memory and then extract it back. The below code is from tutorial02.
  Two problems I'm facing are :
  1. Unless I call SDL_DisplayYUVOverlay, the SDL_SaveBMP function outputs a blank BMP file to the hard disk. How can I output a BMP file without having to call SDL_DisplayYUVOverlay ?
  2. Although I'm able to save the BMP to memory with SDL_SaveBMP_RW and free the memory with filestream->close, I'm unable to load the BMP back from memory with SDL_SaveBMP. The application crashes while trying to load it. Is it because of the c->hidden.unknown.data1=malloc(256); code above ? What would be the right way of allocating this memory ?

    AVFormatContext *pFormatCtx = NULL;
  
    int             i, videoStream;
  
    AVCodecContext  *pCodecCtx = NULL;
  
    AVCodec         *pCodec = NULL;
  
    AVFrame         *pFrame = NULL; 
  
    AVPacket        packet;
  
    SDL_Overlay     *bmp = NULL;
  
    SDL_Surface     *screen = NULL;
  
    SDL_Surface     *screen2 = NULL;
  
    SDL_Rect        rect;
  
  ....
  
  ....    
  
  if(frameFinished) 
  
  
  
  {
  
  SDL_LockYUVOverlay(bmp);//-----------lock
  
  
  
  AVPicture pict;
  
  pict.data[0] = bmp->pixels[0];
  
  pict.data[1] = bmp->pixels[2];
  
  pict.data[2] = bmp->pixels[1];
  
  
  
  pict.linesize[0] = bmp->pitches[0];
  
  pict.linesize[1] = bmp->pitches[2];
  
  pict.linesize[2] = bmp->pitches[1];
  
  
  
  // Convert the image into YUV format that SDL uses
  
  sws_scale( sws_ctx, (uint8_t const * const *)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pict.data, pict.linesize );
  
  
  
  SDL_UnlockYUVOverlay(bmp);//-----------unlock
  
  
  
  rect.x = 0;
  
  rect.y = 0;
  
  rect.w = pCodecCtx->width;
  
  rect.h = pCodecCtx->height;
  
  SDL_DisplayYUVOverlay(bmp, &rect);
  
  ++i;
  
  
  
  SDL_RWops *filestream = MyCustomRWop();//SDL_AllocRW();
  
  SDL_SaveBMP_RW (screen, filestream, i);
  
  screen2 = SDL_LoadBMP_RW(filestream,1);//LOADING IS THE PROBLEM HERE. DON'T KNOW WHY
  
  filestream->close;
  
  SDL_SaveBMP(screen, filepointer);

• Added imageQuality option, which is passed to the canvas.toBlob method to save resized images.

  8 novembre 2013, par blueimp

  Added imageQuality option, which is passed to the canvas.toBlob method to save resized images.
  Removed mozGetAsFile code from the image processing plugin, as Firefox
  
  supports setting the FormData filename since version 22 (current
  
  version being 25).
  

• ffmpeg : save an mp3 part repeated 3 times

  25 novembre 2013, par Re Maden

  ffmpeg -ss 20s -t 30 -i original.mp3 -acodec copy output.mp3

  This command is cutting 30 seconds of an mp3 file and i also want to repeat the 30s loop 3 times and save to the output.mp3
  Is there anyway to do this in ffmpeg ?