GraphicsNode+Protected.h

#import <CoreGraphics/CoreGraphics.h>

@interface GraphicsNode(Protected)

- (void)requestDrawGraphics;

- (void)drawGraphics:(CGContextRef)context;

@end

GraphicsNode.h

#import "CCNode.h"

@interface GraphicsNode : CCNode
@end

GraphicsNode.m

#import "GraphicsNode.h"
#import "GraphicsNode+Protected.h"
#import "CoreGraphicsExtensions.h"
#import "cocos2d.h"

#define BITS_PER_COMPONENT 8
#define BYTES_PER_PIXEL 4

@interface GraphicsNode ()
@property (nonatomic, assign) CCSprite *sprite;
@property (nonatomic, assign) void *bitmap;
@property (nonatomic, assign) CGSize bitmapSize;
@end

@implementation GraphicsNode

- (void)dealloc {
    if (_bitmap) {
        free(_bitmap);
        _bitmap = NULL;
    }

    [super dealloc];
}

- (void)setContentSize:(CGSize)contentSize {
    [super setContentSize:contentSize];
    [self createBitmap];
    [self requestDrawGraphics];
}

#pragma mark Protected

- (void)drawGraphics:(CGContextRef)context {
    assert(NO);
}

- (void)requestDrawGraphics {
    NSLog(@"requestDrawGraphics");

    if (self.sprite) {
        [self removeChild:self.sprite cleanup:YES];
        self.sprite = nil;
    }

    if (!self.bitmap)
        return;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    CGContextRef context = CGBitmapContextCreate(self.bitmap,
        self.bitmapSize.width,
        self.bitmapSize.height,
        BITS_PER_COMPONENT,
        BYTES_PER_PIXEL * self.bitmapSize.width,
        colorSpace,
        kCGImageAlphaPremultipliedLast);

    [self drawGraphics:context];

    CGImageRef image = CGBitmapContextCreateImage(context);
    CCTexture2D *texture = [[[CCTexture2D alloc] initWithCGImage:image resolutionType:kCCResolutioniPhoneRetinaDisplay] autorelease];
    CCSprite *sprite = [CCSprite spriteWithTexture:texture];

    CGImageRelease(image);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    self.sprite = sprite;
    [self addChild:sprite];
}

#pragma mark Private

- (void)createBitmap {
    if (_bitmap) {
        free(_bitmap);
        _bitmap = NULL;
    }

    self.bitmapSize = CGSizeScale(self.contentSize, CC_CONTENT_SCALE_FACTOR());

    if (CGSizeArea(self.bitmapSize) > 0) {
        if (!(_bitmap = malloc(CGSizeArea(self.bitmapSize)  * BYTES_PER_PIXEL))) {
            [NSException raise:NSGenericException format:@"Out of memory allocating GraphicsNode bitmap"];
        }
    }
}

@end