Core plot: annotation with text and image - objective-c

Question

I would like to add an annotation to my graph composed by a text and an image like this:
I can already display the text ("13" in the picture) but I'm not able to add the image below the text.
I've tried with CPTLayer, CPTBorderedLayer,..., but not of them work as expected.
Here is the code I'm using to display the text:
NSNumber *valueToDisplay = [NSNumber numberWithInt:13];
NSString *valueToDisplayString = [formatter stringFromNumber:valueToDisplay];
CPTTextLayer *textLayer = [[CPTTextLayer alloc] initWithText:valueToDisplayString style:style];
self.priceAnnotation.contentLayer = textLayer;
self.priceAnnotation.anchorPlotPoint = [NSArray arrayWithObjects:[NSNumber numberWithFloat:7.0], [NSNumber numberWithFloat:14.0], nil];
[self.graph.plotAreaFrame.plotArea addAnnotation:self.priceAnnotation];
How can I add the image below the text value ?
This is one of the pieces of code I've tried:
CPTBorderedLayer *immagine = [[CPTBorderedLayer alloc] initWithFrame:CGRectMake(0, 0, 77, 36)];
CPTFill *fillImage = [CPTFill fillWithImage:[CPTImage imageWithCGImage:[[UIImage imageNamed:#"sfondoStima.png"] CGImage]]];
immagine.fill = fillImage;
self.imageAnnotation.contentLayer = immagine;
self.imageAnnotation.anchorPlotPoint = [NSArray arrayWithObjects:[NSNumber numberWithFloat:7.0], [NSNumber numberWithFloat:5.0], nil];
[self.graph.plotAreaFrame.plotArea addAnnotation:self.imageAnnotation];
But this is the result: the bitmap (77x36) is for some reason much bigger than what it should be:
Please give me some help ... I've already tried different tutorial/example I've found but none of them seems to work.
Thanks,
Corrado

Answer 1

CPTTextLayer is a subclass of CPTBorderedLayer. For a simple background like this, I wouldn't bother with an image at all. I'd try something like this (untested):
CPTMutableLineStyle lineStyle = [CPTMutableLineStyle lineStyle];
lineStyle.lineWidth = 2.0;
lineStyle.lineColor = [CPTColor whiteColor];
CPTTextLayer *textLayer = [[CPTTextLayer alloc] initWithText:valueToDisplayString style:style];
textLayer.fill = [CPTFill fillWithColor:[CPTColor blueColor]];
textLayer.cornerRadius = 10.0;
textLayer.borderLineStyle = lineStyle;
Set the padding on the textLayer to control the space between the border line and the text.
If you have more complex needs that requires an image, be sure to set the image scale correctly. [CPTImage imageNamed:] does this for you.