Creating and Displaying Bitmap in CGContextRef

• Mario Gajardo Tassara Creating and Displaying Bitmap in CGContextRef Feb 20 2008, 16:19
  Hi to all,
  
  Im in the process of learning Quartz 2D programming API, and im trying
  to display a tiled image in a NSView, i wrote this code for creating a
  valid bitmap context and a routine for displaying a tiled image, but
  nothing is displayed, im not sure what`s wrong because my printf
  debugging statements show good info about the creation of the
  CGcontext and the loading of the image, any help will be appreciated,
  thanks:
  
  -(CGContextRef)CGCreateImageContext:(int)pixelsWidth pixelsHeight:
  (int)pixelsHeight {
  
  CGContextRef theContext=NULL;
  CGColorSpaceRef colorSpace;
  void *bitmapData;
  int bitmapByteCount;
  int bitmapBytePerRow;
  
  bitmapBytePerRow = (pixelsWidth * 4);
  bitmapByteCount = (bitmapBytePerRow * pixelsHeight);
  
  colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
  bitmapData = malloc(bitmapByteCount);
  
  if(bitmapData == NULL) {
    printf("Error");
    return NULL;
  }
  
  theContext = CGBitmapContextCreate(bitmapData,
      pixelsWidth,
      pixelsHeight,
      8,
      bitmapBytePerRow,
      colorSpace,
      kCGImageAlphaNoneSkipLast);
  
  if(theContext == NULL) {
    free(bitmapData);
    printf("ERROR");
    return NULL;
  }
  
  printf("Context bits per component = %d\nContext bits per pixel = %d
  \n",
           CGBitmapContextGetBitsPerComponent(theContext),
           CGBitmapContextGetBitsPerPixel(theContext));
  
  CGColorSpaceRelease(colorSpace);
  return theContext;
  }
  
  -(void)CGDrawImage:(NSRect)rect {
  
  char *filename={"/Users/mario/Pictures/AVATARS/xxx.jpg"};
  
  int imageWidth,imageHeight;
  
  CGDataProviderRef CGdataProv =
  CGDataProviderCreateWithFilename(filename);
  CGImageRef imageRef =
  CGImageCreateWithJPEGDataProvider
  (CGdataProv,NULL,YES,kCGRenderingIntentDefault);
  
  imageWidth=CGImageGetWidth(imageRef);
  imageHeight=CGImageGetHeight(imageRef);
  
  printf("size w = %d\n",imageWidth);
  printf("size h = %d\n",imageHeight);
  
  CGRect theCGRect=CGRectMake(0,0,imageWidth,imageHeight);
  
  int w=rect.size.width;
  int h=rect.size.height;
  
  CGContextRef theBitmapContext = [self CGCreateImageContext:w
  pixelsHeight:h];
  
  
  if(!CGdataProv) {
    printf("CGdataProvider error \n");
  }
  
  if(!imageRef) {
    printf("CGImage error");
  }
  
  CGFloat r,g,b;
  
  r=(drand48());
  g=(drand48());
  b=(drand48());
  
  CGContextDrawTiledImage(theBitmapContext,theCGRect,imageRef);
  
  char *bitmapData = CGBitmapContextGetData(theBitmapContext);
  
  CGContextRelease(theBitmapContext);
  
  if(bitmapData) {
    free(bitmapData);
  }
  CGImageRelease(imageRef);
  }
• David Duncan Re: Creating and Displaying Bitmap in CGContextRef Feb 20 2008, 20:42
  On Feb 20, 2008, at 7:19 AM, Mario Gajardo Tassara wrote:
  
  

  > Im in the process of learning Quartz 2D programming API, and im
  > trying to display a tiled image in a NSView, i wrote this code for
  > creating a valid bitmap context and a routine for displaying a tiled
  > image, but nothing is displayed, im not sure what`s wrong because my
  > printf debugging statements show good info about the creation of the
  > CGcontext and the loading of the image, any help will be
  > appreciated, thanks:
  

  
  Your not drawing into the window at all. You need to get the CGContext
  to draw to from the current NSGraphicsContext via:
  
  CGContextRef context = (CGContextRef)[[NSGraphicsContext
  currentContext] graphicsPort];
  
  The bitmap context stuff you have looks like a red herring.
  --
  David Duncan
  Apple DTS Animation and Printing
  <david.duncan...>
• Mario Gajardo Tassara Re: Creating and Displaying Bitmap in CGContextRef Feb 20 2008, 23:38
  Thanks David and Chris, your answers help me a lot , now my app draws
  to the screen :)
  
  El 20-02-2008, a las 16:42, David Duncan escribió:
  
  

  > On Feb 20, 2008, at 7:19 AM, Mario Gajardo Tassara wrote:
  >
  >> Im in the process of learning Quartz 2D programming API, and im
  >> trying to display a tiled image in a NSView, i wrote this code for
  >> creating a valid bitmap context and a routine for displaying a
  >> tiled image, but nothing is displayed, im not sure what`s wrong
  >> because my printf debugging statements show good info about the
  >> creation of the CGcontext and the loading of the image, any help
  >> will be appreciated, thanks:
  >
  >
  > Your not drawing into the window at all. You need to get the
  > CGContext to draw to from the current NSGraphicsContext via:
  >
  > CGContextRef context = (CGContextRef)[[NSGraphicsContext
  > currentContext] graphicsPort];
  >
  > The bitmap context stuff you have looks like a red herring.
  > --
  > David Duncan
  > Apple DTS Animation and Printing
  > <david.duncan...>
  >
  >
  >