An extension for Sparrow that allows 9-slice scaling of images and buttons.

XDImage.h

//
//  XDImage.h
//  XDImage
//
//  Created by Shilo White on 8/26/13.
//
//

#import "SPDisplayObjectContainer.h"
#import "SPButton.h"
#import "SPRectangle.h"
@class SPTexture;

@interface XDImage : SPDisplayObjectContainer

- (id)initWithContentsOfFile:(NSString *)path;
- (id)initWithContentsOfFile:(NSString *)path generateMipmaps:(BOOL)mipmaps;
- (id)initWithTexture:(SPTexture *)texture;

- (id)initWithWidth:(float)width height:(float)height;
- (id)initWithWidth:(float)width height:(float)height color:(uint)color;
- (id)initWithWidth:(float)width height:(float)height color:(uint)color premultipliedAlpha:(BOOL)pma;

+ (id)imageWithContentsOfFile:(NSString *)path;
+ (id)imageWithContentsOfFile:(NSString *)path generateMipmaps:(BOOL)mipmaps;
+ (id)imageWithTexture:(SPTexture *)texture;

+ (id)image;
+ (id)imageWithWidth:(float)width height:(float)height;
+ (id)imageWithWidth:(float)width height:(float)height color:(uint)color;
+ (id)imageWithWidth:(float)width height:(float)height color:(uint)color premultipliedAlpha:(BOOL)pma;

@property (nonatomic, strong) SPTexture *texture;
@property (nonatomic, copy) SPRectangle *scale9Grid;
@property (nonatomic, assign) BOOL debugDraw;
@property (nonatomic, assign) uint color;
@property (nonatomic, readonly) BOOL tinted;
@property (nonatomic, assign) BOOL premultipliedAlpha;

@end

@interface XDButton : SPButton

@property (nonatomic, copy) SPRectangle *scale9Grid;
@property (nonatomic, assign) BOOL debugDraw;

@end

@interface SPRectangle (XDImage)

+ (SPRectangle *)rectangleCenteredToBounds:(SPRectangle *)bounds;
+ (SPRectangle *)rectangleCenteredToBounds:(SPRectangle *)bounds width:(float)width height:(float)height;

@end

XDImage.m

//
//  XDImage.m
//  XDImage
//
//  Created by Shilo White on 8/26/13.
//
//

#import "XDImage.h"
#import "SPTexture.h"
#import "SPImage.h"
#import "SPQuad.h"
#import "SPDisplayObject.h"

@implementation XDImage
{
    SPTexture *_texture;
    SPRectangle *_scale9Grid;
    BOOL _debugDraw;
    SPQuad *_debugDrawQuad;
    SPImage *_images[9];
    float _originalPivotX;
    float _originalPivotY;
    BOOL _tinted;
}

@synthesize texture = _texture;
@synthesize scale9Grid = _scale9Grid;
@synthesize debugDraw = _debugDraw;

- (id)initWithContentsOfFile:(NSString *)path
{
    return [self initWithContentsOfFile:path generateMipmaps:NO];
}

- (id)initWithContentsOfFile:(NSString *)path generateMipmaps:(BOOL)mipmaps
{
    return [self initWithTexture:[SPTexture textureWithContentsOfFile:path generateMipmaps:mipmaps]];
}

- (id)initWithTexture:(SPTexture *)texture
{
    if (!texture) [NSException raise:SP_EXC_INVALID_OPERATION format:@"texture cannot be nil!"];
    
    if ((self = [super init]))
    {
        _texture = texture;
        _images[0] = [[SPImage alloc] initWithTexture:_texture];
        [self addChild:_images[0]];
    }
    return self;
}

- (id)init
{
    return [self initWithWidth:32 height:32];
}

- (id)initWithWidth:(float)width height:(float)height
{
    return [self initWithTexture:[SPTexture textureWithWidth:width height:height draw:NULL]];
}

- (id)initWithWidth:(float)width height:(float)height color:(uint)color
{
    return [self initWithWidth:width height:height color:color premultipliedAlpha:YES];
}

- (id)initWithWidth:(float)width height:(float)height color:(uint)color premultipliedAlpha:(BOOL)pma
{
    if ((self = [super init]))
    {
        _texture = nil;
        _images[0] = [[SPImage alloc] initWithTexture:_texture];
        [self addChild:_images[0]];
    }
    return self;
}

- (void)recreateImages
{
    if (_scale9Grid)
    {
        for (int i=1; i<9; i++)
        {
            [_images[i] removeFromParent];
            _images[i] = nil;
            
            SPRectangle *region = [self textureRegionForIndex:i];
            if (region.width && region.height)
            {
                SPTexture *texture = [SPTexture textureWithRegion:region ofTexture:_texture];
                _images[i] = [[SPImage alloc] initWithTexture:texture];
                _images[i].x = region.x;
                _images[i].y = region.y;
                [self addChild:_images[i]];
            }
        }
        _images[0].texture = [SPTexture textureWithRegion:_scale9Grid ofTexture:_texture];
        _images[0].x = _scale9Grid.x;
        _images[0].y = _scale9Grid.y;
        [_images[0] readjustSize];
    }
    else
    {
        for (int i=8; i>0; i--)
        {
            [_images[i] removeFromParent];
            _images[i] = nil;
        }
        _images[0].texture = _texture;
        _images[0].x = _images[0].y = 0;
        [_images[0] readjustSize];
    }
}

- (SPRectangle *)textureRegionForIndex:(uint)index
{
    float x, y, width, height;
    x = y = width = height = 0.0f;
    
    switch (index) {
        case 1:
            width = _scale9Grid.x;
            height = _scale9Grid.y;
            break;
        case 2:
            x = _scale9Grid.x;
            width = _scale9Grid.width;
            height = _scale9Grid.y;
            break;
        case 3:
            x = _scale9Grid.x+_scale9Grid.width;
            width = _texture.width-x;
            height = _scale9Grid.y;
            break;
        case 4:
            y = _scale9Grid.y;
            width = _scale9Grid.x;
            height = _scale9Grid.height;
            break;
        case 5:
            x = _scale9Grid.x+_scale9Grid.width;
            y = _scale9Grid.y;
            width = _texture.width-x;
            height = _scale9Grid.height;
            break;
        case 6:
            y = _scale9Grid.y+_scale9Grid.height;
            width = _scale9Grid.x;
            height = _texture.height-y;
            break;
        case 7:
            x = _scale9Grid.x;
            y = _scale9Grid.y+_scale9Grid.height;
            width = _scale9Grid.width;
            height = _texture.height-y;
            break;
        case 8:
            x = _scale9Grid.x+_scale9Grid.width;
            y = _scale9Grid.y+_scale9Grid.height;
            width = _texture.width-x;
            height = _texture.height-y;
            break;
    }
    
    return [SPRectangle rectangleWithX:x y:y width:width height:height];
}

- (void)setTexture:(SPTexture *)texture
{
    if (texture == nil)
    {
        [NSException raise:SP_EXC_INVALID_OPERATION format:@"texture cannot be nil!"];
    }
    else if (texture != _texture)
    {
        _texture = texture;;
        [self recreateImages];
    }
}

- (void)setScale9Grid:(SPRectangle *)scale9Grid
{
    BOOL shouldRecreateImages = ((_scale9Grid != nil) || (scale9Grid != nil));
    _scale9Grid = [scale9Grid copy];
    if (shouldRecreateImages) [self recreateImages];
    if (_debugDraw) [self alignDebugDrawQuad];
}

- (void)setDebugDraw:(BOOL)debugDraw
{
    if (debugDraw != _debugDraw)
    {
        _debugDraw = debugDraw;
        if (_debugDraw)
        {
            _debugDrawQuad = [SPQuad quad];
            _debugDrawQuad.color = 0x00ff00;
            _debugDrawQuad.alpha = 0.5f;
            [self alignDebugDrawQuad];
            [self addChild:_debugDrawQuad];
        }
        else
        {
            [_debugDrawQuad removeFromParent];
            _debugDrawQuad = nil;
        }
    }
}

- (void)alignDebugDrawQuad
{
    if (_scale9Grid)
    {
        _debugDrawQuad.x = _scale9Grid.x;
        _debugDrawQuad.y = _scale9Grid.y;
        _debugDrawQuad.width = _scale9Grid.width;
        _debugDrawQuad.height = _scale9Grid.height;
    }
    _debugDrawQuad.visible = (BOOL)_scale9Grid;
}

- (void)setScaleX:(float)scaleX
{
    if (_scale9Grid)
    {
        float targetWidth = _texture.width * scaleX;
        float middleTargetWidth = targetWidth - _images[4].texture.width - _images[5].texture.width;
        
        float middleScaleX = 0.0f;
        float sideScaleX = 1.0f;
        if(middleTargetWidth < 0.0f)
            sideScaleX = scaleX*(_texture.width/(_images[4].texture.width+_images[5].texture.width));
        else
            middleScaleX = middleTargetWidth / _images[0].texture.width;
        
        //left
        _images[1].scaleX = _images[4].scaleX = _images[6].scaleX = sideScaleX;
        //middle
        _images[0].x = _images[2].x = _images[7].x = _images[1].width;
        _images[0].scaleX = _images[2].scaleX = _images[7].scaleX = middleScaleX;
        //right
        _images[3].x = _images[5].x = _images[8].x = _images[0].x + _images[0].width;
        _images[3].scaleX = _images[5].scaleX = _images[8].scaleX = sideScaleX;
        
        if (_debugDraw)
        {
            _debugDrawQuad.x = _images[0].x;
            _debugDrawQuad.width = _images[0].width;
        }
    }
    else
        _images[0].scaleX = scaleX;
    
    if (_originalPivotX)
        [super setPivotX:self.width*(_originalPivotX/_texture.width)];
}

- (void)setScaleY:(float)scaleY
{
    if (_scale9Grid)
    {
        float targetHeight = _texture.height * scaleY;
        float middleTargetHeight = targetHeight - _images[2].texture.height - _images[7].texture.height;
        
        float middleScaleY = 0.0f;
        float sideScaleY = 1.0f;
        if(middleTargetHeight < 0.0f)
            sideScaleY = scaleY*(_texture.height/(_images[2].texture.height+_images[7].texture.height));
        else
            middleScaleY = middleTargetHeight / _images[0].texture.height;
        
        //top
        _images[1].scaleY = _images[2].scaleY = _images[3].scaleY = sideScaleY;
        //middle
        _images[0].y = _images[4].y = _images[5].y = _images[1].height;
        _images[0].scaleY = _images[4].scaleY = _images[5].scaleY = middleScaleY;
        //bottom
        _images[6].y = _images[7].y = _images[8].y = _images[0].y + _images[0].height;
        _images[6].scaleY = _images[7].scaleY = _images[8].scaleY = sideScaleY;
        
        if (_debugDraw)
        {
            _debugDrawQuad.y = _images[0].y;
            _debugDrawQuad.height = _images[0].height;
        }
    }
    else
        _images[0].scaleY = scaleY;
    
    if (_originalPivotY)
        [super setPivotY:self.height*(_originalPivotY/_texture.height)];
}

- (void)setPivotX:(float)pivotX
{
    if (pivotX != _originalPivotX)
    {
        _originalPivotX = pivotX;
        [super setPivotX:self.width*(pivotX/_texture.width)];
    }
}

- (float)pivotX
{
    return _originalPivotX;
}

- (void)setPivotY:(float)pivotY
{
    if (pivotY != _originalPivotY)
    {
        _originalPivotY = pivotY;
        [super setPivotY:self.height*(pivotY/_texture.height)];
    }
}

- (float)pivotY
{
    return _originalPivotY;
}

- (void)setColor:(uint)color
{
    for (int i=0; i<9; i++)
        _images[i].color = color;
    
    if (color != 0xffffff) _tinted = YES;
    else _tinted = (self.alpha != 1.0f) || _images[0].tinted;
}

- (uint)color
{
    return _images[0].color;
}

- (void)setAlpha:(float)alpha
{
    super.alpha = alpha;
    
    if (self.alpha != 1.0f) _tinted = true;
    else _tinted = _images[0].tinted;
}

- (BOOL)tinted
{
    return _tinted;
}

- (void)setPremultipliedAlpha:(BOOL)premultipliedAlpha
{
    for (int i=0; i<9; i++)
        _images[i].premultipliedAlpha = premultipliedAlpha;
}

- (BOOL)premultipliedAlpha
{
    return _images[0].premultipliedAlpha;
}

- (void)addChild:(SPDisplayObject *)child
{
    [super addChild:child];
    if (_debugDraw) [super addChild:_debugDrawQuad];
}

+ (id)imageWithContentsOfFile:(NSString *)path
{
    return [[self alloc] initWithContentsOfFile:path];
}

+ (id)imageWithContentsOfFile:(NSString *)path generateMipmaps:(BOOL)mipmaps
{
    return [[self alloc] initWithContentsOfFile:path generateMipmaps:mipmaps];
}

+ (id)imageWithTexture:(SPTexture *)texture
{
    return [[self alloc] initWithTexture:texture];
}

+ (id)image
{
    return [[self alloc] init];
}

+ (id)imageWithWidth:(float)width height:(float)height
{
    return [[self alloc] initWithWidth:width height:height];
}

+ (id)imageWithWidth:(float)width height:(float)height color:(uint)color
{
    return [[self alloc] initWithWidth:width height:height color:color];
}

+ (id)imageWithWidth:(float)width height:(float)height color:(uint)color premultipliedAlpha:(BOOL)pma
{
    return [[self alloc] initWithWidth:width height:height color:color premultipliedAlpha:pma];
}

@end

@interface SPButton ()
{
    @protected
    XDImage *_background;
    SPSprite *_contents;
}

@end

@implementation XDButton
{
    float _originalPivotX;
    float _originalPivotY;
}

- (id)initWithUpState:(SPTexture*)upState downState:(SPTexture*)downState
{
    if ((self = [super initWithUpState:upState downState:downState]))
    {
        [_background removeFromParent];
        _background = [XDImage imageWithTexture:upState];
        [_contents addChild:_background atIndex:0];
    }
    return self;
}

- (void)setScale9Grid:(SPRectangle *)scale9Grid
{
    [_background setScale9Grid:scale9Grid];
}

- (SPRectangle *)scale9Grid
{
    return [_background scale9Grid];
}

- (void)setDebugDraw:(BOOL)debugDraw
{
    [_background setDebugDraw:debugDraw];
}

- (BOOL)debugDraw
{
    return [_background debugDraw];
}

- (void)setWidth:(float)width
{
    [super setWidth:width];
    
    if (_originalPivotX)
        [super setPivotX:self.width*(_originalPivotX/_background.texture.width)];
}

- (void)setHeight:(float)height
{
    [super setHeight:height];
    
    if (_originalPivotY)
        [super setPivotY:self.height*(_originalPivotY/_background.texture.height)];
}

- (void)setScaleX:(float)scaleX
{
    [_background setScaleX:scaleX];
    
    if (_originalPivotX)
        [super setPivotX:self.width*(_originalPivotX/_background.texture.width)];
}

- (float)scaleX
{
    return [_background scaleX];
}

- (void)setScaleY:(float)scaleY
{
    [_background setScaleY:scaleY];
    
    if (_originalPivotY)
        [super setPivotY:self.height*(_originalPivotY/_background.texture.height)];
}

- (float)scaleY
{
    return [_background scaleY];
}

- (void)setPivotX:(float)pivotX
{
    if (pivotX != _originalPivotX)
    {
        _originalPivotX = pivotX;
        [super setPivotX:self.width*(pivotX/_background.texture.width)];
    }
}

- (float)pivotX
{
    return _originalPivotX;
}

- (void)setPivotY:(float)pivotY
{
    if (pivotY != _originalPivotY)
    {
        _originalPivotY = pivotY;
        [super setPivotY:self.height*(pivotY/_background.texture.height)];
    }
}

- (float)pivotY
{
    return _originalPivotY;
}

@end

@implementation SPRectangle (XDImage)

+ (SPRectangle *)rectangleCenteredToBounds:(SPRectangle *)bounds
{
    return [self rectangleCenteredToBounds:bounds width:1.0f height:1.0f];
}

+ (SPRectangle *)rectangleCenteredToBounds:(SPRectangle *)bounds width:(float)width height:(float)height
{
    return [SPRectangle rectangleWithX:(int)((bounds.width-width)/2.0f) y:(int)((bounds.height-height)/2.0f) width:width height:height];
}

@end