A Codea addon for saving images to the photo album, share photos to facebook and detect faces in an image. Just add [self.viewController registerAddon:[ImageTools sharedInstance]]; to AppDelegate.mm

ImageTools.h

//
//  ImageTools.h
//  FaceDetection
//
//  Created by Tobias Teleman on fredag 12 april 2013
//  Copyright (c) Tobias Teleman. All rights reserved.
//

#import <Foundation/Foundation.h>

#import "CodeaAddon.h"

#define DEFINE_SHARED_INSTANCE_USING_BLOCK(block) \
+ (instancetype)sharedInstance\
{\
static dispatch_once_t pred = 0; \
__strong static id _sharedObject = nil; \
dispatch_once(&pred, ^{ \
_sharedObject = block(); \
}); \
return _sharedObject; \
}\


#define DEFINE_SHARED_INSTANCE \
+ (instancetype)sharedInstance;\


#define DEFINE_SHARED_INSTANCE_IMPL \
DEFINE_SHARED_INSTANCE_USING_BLOCK(^{\
return [[self alloc] init];\
})\

@interface ImageTools: NSObject<CodeaAddon>

DEFINE_SHARED_INSTANCE

@end

ImageTools.mm

//
//  ImageTools.mm
//  FaceDetection
//
//  Created by Tobias Teleman on fredag 12 april 2013
//  Copyright (c) Tobias Teleman. All rights reserved.
//

#import "ImageTools.h"
#import "Social/Social.h"

#ifdef __cplusplus
extern "C" {
#endif

#import "lua.h"
#import "lauxlib.h"

struct image_type_t;
struct image_type_t *checkimage(lua_State *L, int i);

typedef enum PersistenceImageAlpha
{
    PersistenceImageAlphaPremultiply,
    PersistenceImageAlphaNoPremultiply,
} PersistenceImageAlpha;

UIImage* createUIImageFromImage(struct image_type_t* image, PersistenceImageAlpha alphaOption);
    
#ifdef __cplusplus
}
#endif

static int WriteToPhotoAlbumFunction(struct lua_State *state);
static int ShareToFacebook(struct lua_State *state);
static int DetectFaceFeatures(struct lua_State *state);

@interface ImageTools()

@property (nonatomic, weak) CodeaViewController *codeaViewController;
@property (nonatomic, strong) CIDetector* detector;

@end

@implementation ImageTools

DEFINE_SHARED_INSTANCE_IMPL

- (void) codea:(CodeaViewController*)controller didCreateLuaState:(struct lua_State*)L
{
    NSLog(@"Register ImageTools");
    self.codeaViewController = controller;
    lua_register(L, "saveToPhotoAlbum", WriteToPhotoAlbumFunction);
    lua_register(L, "shareToFacebook", ShareToFacebook);
    lua_register(L, "detectFaceFeatures", DetectFaceFeatures);
    
    NSDictionary *detectorOptions = [[NSDictionary alloc] initWithObjectsAndKeys:CIDetectorAccuracyLow, CIDetectorAccuracy, nil];
    self.detector = [CIDetector detectorOfType:CIDetectorTypeFace
                                              context:nil options:detectorOptions];
}
@end

static int WriteToPhotoAlbumFunction(struct lua_State *state) {
    struct image_type_t* imageType = checkimage(state, 1);
    UIImage* image = createUIImageFromImage(imageType, PersistenceImageAlphaNoPremultiply);
    UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
    return 0;
}

static int ShareToFacebook(struct lua_State *state) {
    SLComposeViewController *fbController=[SLComposeViewController composeViewControllerForServiceType:SLServiceTypeFacebook];
    struct image_type_t* imageType = checkimage(state, 1);
    UIImage* image = createUIImageFromImage(imageType, PersistenceImageAlphaNoPremultiply);
    
    if([SLComposeViewController isAvailableForServiceType:SLServiceTypeFacebook])
    {
        SLComposeViewControllerCompletionHandler __block completionHandler=^(SLComposeViewControllerResult result){
            
            [fbController dismissViewControllerAnimated:YES completion:nil];
            
            switch(result){
                case SLComposeViewControllerResultCancelled:
                default:
                {
                    NSLog(@"Cancelled");
                    
                }
                    break;
                case SLComposeViewControllerResultDone:
                {
                    NSLog(@"Posted");
                }
                    break;
            }};
        
        [fbController addImage:image];
        [fbController setInitialText:@"I made this with Recursive!"];
        [fbController setCompletionHandler:completionHandler];
        [[ImageTools sharedInstance].codeaViewController
            presentViewController:fbController animated:YES completion:nil];
    }
    return 0;
}

static int DetectFaceFeatures(struct lua_State *state) {
    struct image_type_t* imageType = checkimage(state, 1);
    UIImage* image = createUIImageFromImage(imageType, PersistenceImageAlphaNoPremultiply);
    CIImage* ciimage = [CIImage imageWithCGImage:image.CGImage];
    NSArray* features = [[ImageTools sharedInstance].detector featuresInImage:ciimage];
    for(CIFaceFeature* faceFeature in features) {
        lua_newtable(state);
        lua_pushstring(state, "x");
        lua_pushinteger(state, faceFeature.bounds.origin.x);
        lua_settable(state, -3);

        lua_pushstring(state, "y");
        lua_pushinteger(state, faceFeature.bounds.origin.y);
        lua_settable(state, -3);
        
        lua_pushstring(state, "width");
        lua_pushinteger(state, faceFeature.bounds.size.width);
        lua_settable(state, -3);
        
        lua_pushstring(state, "height");
        lua_pushinteger(state, faceFeature.bounds.size.height);
        lua_settable(state, -3);

        if(faceFeature.hasLeftEyePosition) {
            lua_pushstring(state, "leftEye");
            
            lua_newtable(state);
            lua_pushstring(state, "x");
            lua_pushinteger(state, faceFeature.leftEyePosition.x);
            lua_settable(state, -3);

            lua_pushstring(state, "y");
            lua_pushinteger(state, faceFeature.leftEyePosition.y);
            lua_settable(state, -3);
            
            lua_settable(state, -3);
        }
        if(faceFeature.hasRightEyePosition) {
            lua_pushstring(state, "rightEye");
            
            lua_newtable(state);
            lua_pushstring(state, "x");
            lua_pushinteger(state, faceFeature.rightEyePosition.x);
            lua_settable(state, -3);
            
            lua_pushstring(state, "y");
            lua_pushinteger(state, faceFeature.rightEyePosition.y);
            lua_settable(state, -3);
            
            lua_settable(state, -3);

        }
        
        if(faceFeature.hasMouthPosition) {
            lua_pushstring(state, "mouth");
            
            lua_newtable(state);
            lua_pushstring(state, "x");
            lua_pushinteger(state, faceFeature.mouthPosition.x);
            lua_settable(state, -3);
            
            lua_pushstring(state, "y");
            lua_pushinteger(state, faceFeature.mouthPosition.y);
            lua_settable(state, -3);
            
            lua_settable(state, -3);
        }
        
        return 1;
    }    
    return 0;
}