/*

     File: ImageScrollView.m

 Abstract: Centers image within the scroll view and configures image sizing and display.

  Version: 1.3

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 */

#import <Foundation/Foundation.h>

#import "ImageScrollView.h"

#import "TilingView.h"

#define TILE_IMAGES 1  // turn on to use tiled images, if off, we use whole images

// forward declaration of our utility functions

static NSUInteger _ImageCount(void);

#if TILE_IMAGES

static CGSize _ImageSizeAtIndex(NSUInteger index);

static UIImage *_PlaceholderImageNamed(NSString *name);

#endif

#if !TILE_IMAGES

static UIImage *_ImageAtIndex(NSUInteger index);

#endif

static NSString *_ImageNameAtIndex(NSUInteger index);

#pragma mark -

@interface ImageScrollView () <UIScrollViewDelegate>

{

    UIImageView *_zoomView;  // if tiling, this contains a very low-res placeholder image,

                             // otherwise it contains the full image.

    CGSize _imageSize;

#if TILE_IMAGES

    TilingView *_tilingView;

#endif

    CGPoint _pointToCenterAfterResize;

    CGFloat _scaleToRestoreAfterResize;

}

@end

@implementation ImageScrollView

- (id)initWithFrame:(CGRect)frame

{

    self = [super initWithFrame:frame];

    if (self)

    {

        self.showsVerticalScrollIndicator = NO;

        self.showsHorizontalScrollIndicator = NO;

        self.bouncesZoom = YES;

        self.decelerationRate = UIScrollViewDecelerationRateFast;

        self.delegate = self;        

    }

    return self;

}

- (void)setIndex:(NSUInteger)index

{

    _index = index;

#if TILE_IMAGES

    [self displayTiledImageNamed:_ImageNameAtIndex(index) size:_ImageSizeAtIndex(index)];

#else

    [self displayImage:_ImageAtIndex(index)];

#endif

}

+ (NSUInteger)imageCount

{

    return _ImageCount();

}

- (void)layoutSubviews 

{

    [super layoutSubviews];

    // center the zoom view as it becomes smaller than the size of the screen

    CGSize boundsSize = self.bounds.size;

    CGRect frameToCenter = _zoomView.frame;

    // center horizontally

    if (frameToCenter.size.width < boundsSize.width)

        frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2;

    else

        frameToCenter.origin.x = 0;

    // center vertically

    if (frameToCenter.size.height < boundsSize.height)

        frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2;

    else

        frameToCenter.origin.y = 0;

    _zoomView.frame = frameToCenter;

}

- (void)setFrame:(CGRect)frame

{

    BOOL sizeChanging = !CGSizeEqualToSize(frame.size, self.frame.size);

    if (sizeChanging) {

        [self prepareToResize];

    }

    [super setFrame:frame];

    if (sizeChanging) {

        [self recoverFromResizing];

    }

}

#pragma mark - UIScrollViewDelegate

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView

{

    return _zoomView;

}

#pragma mark - Configure scrollView to display new image (tiled or not)

#if TILE_IMAGES

- (void)displayTiledImageNamed:(NSString *)imageName size:(CGSize)imageSize

{

    // clear views for the previous image

    [_zoomView removeFromSuperview];

    _zoomView = nil;

    _tilingView = nil;

    // reset our zoomScale to 1.0 before doing any further calculations

    self.zoomScale = 1.0;

    // make views to display the new image

    _zoomView = [[UIImageView alloc] initWithFrame:(CGRect){ CGPointZero, imageSize }];

    [_zoomView setImage:_PlaceholderImageNamed(imageName)];

    [self addSubview:_zoomView];

    _tilingView = [[TilingView alloc] initWithImageName:imageName size:imageSize];

    _tilingView.frame = _zoomView.bounds;

    [_zoomView addSubview:_tilingView];

    [self configureForImageSize:imageSize];

}

#else

- (void)displayImage:(UIImage *)image

{

    // clear the previous image

    [_zoomView removeFromSuperview];

    _zoomView = nil;

    // reset our zoomScale to 1.0 before doing any further calculations

    self.zoomScale = 1.0;

    // make a new UIImageView for the new image

    _zoomView = [[UIImageView alloc] initWithImage:image];

    [self addSubview:_zoomView];

    [self configureForImageSize:image.size];

}

#endif // TILE_IMAGES

- (void)configureForImageSize:(CGSize)imageSize

{

    _imageSize = imageSize;

    self.contentSize = imageSize;

    [self setMaxMinZoomScalesForCurrentBounds];

    self.zoomScale = self.minimumZoomScale;

}

- (void)setMaxMinZoomScalesForCurrentBounds

{

    CGSize boundsSize = self.bounds.size;

    // calculate min/max zoomscale

    CGFloat xScale = boundsSize.width  / _imageSize.width;    // the scale needed to perfectly fit the image width-wise

    CGFloat yScale = boundsSize.height / _imageSize.height;   // the scale needed to perfectly fit the image height-wise

    // fill width if the image and phone are both portrait or both landscape; otherwise take smaller scale

    BOOL imagePortrait = _imageSize.height > _imageSize.width;

    BOOL phonePortrait = boundsSize.height > boundsSize.width;

    CGFloat minScale = imagePortrait == phonePortrait ? xScale : MIN(xScale, yScale);

    // on high resolution screens we have double the pixel density, so we will be seeing every pixel if we limit the

    // maximum zoom scale to 0.5.

    CGFloat maxScale = 1.0 / [[UIScreen mainScreen] scale];

    // don't let minScale exceed maxScale. (If the image is smaller than the screen, we don't want to force it to be zoomed.) 

    if (minScale > maxScale) {

        minScale = maxScale;

    }

    self.maximumZoomScale = maxScale;

    self.minimumZoomScale = minScale;

}

#pragma mark -

#pragma mark Methods called during rotation to preserve the zoomScale and the visible portion of the image

#pragma mark - Rotation support

- (void)prepareToResize

{

    CGPoint boundsCenter = CGPointMake(CGRectGetMidX(self.bounds), CGRectGetMidY(self.bounds));

    _pointToCenterAfterResize = [self convertPoint:boundsCenter toView:_zoomView];

    _scaleToRestoreAfterResize = self.zoomScale;

    // If we're at the minimum zoom scale, preserve that by returning 0, which will be converted to the minimum

    // allowable scale when the scale is restored.

    if (_scaleToRestoreAfterResize <= self.minimumZoomScale + FLT_EPSILON)

        _scaleToRestoreAfterResize = 0;

}

- (void)recoverFromResizing

{

    [self setMaxMinZoomScalesForCurrentBounds];

    // Step 1: restore zoom scale, first making sure it is within the allowable range.

    CGFloat maxZoomScale = MAX(self.minimumZoomScale, _scaleToRestoreAfterResize);

    self.zoomScale = MIN(self.maximumZoomScale, maxZoomScale);

    // Step 2: restore center point, first making sure it is within the allowable range.

    // 2a: convert our desired center point back to our own coordinate space

    CGPoint boundsCenter = [self convertPoint:_pointToCenterAfterResize fromView:_zoomView];

    // 2b: calculate the content offset that would yield that center point

    CGPoint offset = CGPointMake(boundsCenter.x - self.bounds.size.width / 2.0,

                                 boundsCenter.y - self.bounds.size.height / 2.0);

    // 2c: restore offset, adjusted to be within the allowable range

    CGPoint maxOffset = [self maximumContentOffset];

    CGPoint minOffset = [self minimumContentOffset];

    CGFloat realMaxOffset = MIN(maxOffset.x, offset.x);

    offset.x = MAX(minOffset.x, realMaxOffset);

    realMaxOffset = MIN(maxOffset.y, offset.y);

    offset.y = MAX(minOffset.y, realMaxOffset);

    self.contentOffset = offset;

}

- (CGPoint)maximumContentOffset

{

    CGSize contentSize = self.contentSize;

    CGSize boundsSize = self.bounds.size;

    return CGPointMake(contentSize.width - boundsSize.width, contentSize.height - boundsSize.height);

}

- (CGPoint)minimumContentOffset

{

    return CGPointZero;

}

@end

static NSArray *_ImageData(void)

{

    static NSArray *data = nil;

    static dispatch_once_t onceToken;

    dispatch_once(&onceToken, ^{

        NSString *path = [[NSBundle mainBundle] pathForResource:@"ImageData" ofType:@"plist"];

        NSData *plistData = [NSData dataWithContentsOfFile:path];

        NSString *error; NSPropertyListFormat format;

        data = [NSPropertyListSerialization propertyListFromData:plistData

                                                mutabilityOption:NSPropertyListImmutable

                                                          format:&format

                                                errorDescription:&error];

        if (!data) {

            NSLog(@"Unable to read image data: %@", error);

        }

    });

    return data;

}

static NSUInteger _ImageCount(void)

{

    static NSUInteger count = 0;

    static dispatch_once_t onceToken;

    dispatch_once(&onceToken, ^{

        count = [_ImageData() count];

    });

    return count;

}

static NSString *_ImageNameAtIndex(NSUInteger index)

{

    NSDictionary *info = [_ImageData() objectAtIndex:index];

    return [info valueForKey:@"name"];

}

#if !TILE_IMAGES

// we use "imageWithContentsOfFile:" instead of "imageNamed:" here to avoid caching

static UIImage *_ImageAtIndex(NSUInteger index)

{

    NSString *imageName = _ImageNameAtIndex(index);

    NSString *path = [[NSBundle mainBundle] pathForResource:imageName ofType:@"jpg"];

    return [UIImage imageWithContentsOfFile:path];

}

#endif

#if TILE_IMAGES

static CGSize _ImageSizeAtIndex(NSUInteger index)

{

    NSDictionary *info = [_ImageData() objectAtIndex:index];

    return CGSizeMake([[info valueForKey:@"width"] floatValue],

                      [[info valueForKey:@"height"] floatValue]);

}

static UIImage *_PlaceholderImageNamed(NSString *name)

{

    return [UIImage imageNamed:[NSString stringWithFormat:@"%@_Placeholder", name]];

}

#endif