切り取り範囲の矩形を選択するクラス

TrimmingSquareView.h

#import <UIKit/UIKit.h>

@interface TrimmingSquareView : UIView

@property (nonatomic, readonly) CGRect trimmngRect;

- (void)resetPosition;

@end

TrimmingSquareView.m

#import "TrimmingSquareView.h"

#define DEFAULT_EDGE_SIZE 50
#define MIM_EDGE_SIZE 20

@interface TrimmingSquareView()
{
    CGRect trimRange;
    CGPoint lastTouchPoint;;
    CGSize cornerRectSize;
    
    CGRect cornerRectTopLeft;
    CGRect cornerRectTopRight;
    CGRect cornerRectBottomLeft;
    CGRect cornerRectBottomRight;
    
    BOOL isRangeResizing;
    BOOL isRangeMoving;
    BOOL isTouchedLeftCorner;
}

@end

@implementation TrimmingSquareView

@synthesize trimmngRect = trimRange;

/**
 * 初期化
 *
 */
- (instancetype)init
{
    self = [super init];
    if (self) {
        isRangeResizing = NO;
        isRangeMoving   = NO;
        trimRange       = CGRectZero;
        lastTouchPoint  = CGPointZero;
        cornerRectSize  = CGSizeMake(10, 10);
        
        self.backgroundColor = [UIColor clearColor];
    }
    return self;
}

/**
 * 切り取り矩形範囲のリセット
 *
 */
- (void)resetPosition
{
    trimRange = CGRectMake((self.frame.size.width * 0.5) - (DEFAULT_EDGE_SIZE * 0.5),
                                (self.frame.size.height * 0.5) - (DEFAULT_EDGE_SIZE * 0.5),
                                DEFAULT_EDGE_SIZE,
                                DEFAULT_EDGE_SIZE);
    [self setNeedsDisplay];
}

/**
 * 切り取り矩形範囲の描画
 *
 */
- (void)drawRect:(CGRect)rect {
    
    // 切り取り範囲の表示
    UIBezierPath *rangeRectPath = [UIBezierPath bezierPathWithRect:trimRange];
    [[UIColor redColor] setStroke];
    rangeRectPath.lineWidth = 0.5;
    CGFloat dashPattern[2] = {4.0f, 1.0f};
    [rangeRectPath setLineDash:dashPattern count:2 phase:0];
    [rangeRectPath stroke];
    
    // 切り取り範囲の角の四角部分
    UIBezierPath *cornerRectPath;
    
    // 左上
    cornerRectTopLeft.size = cornerRectSize;
    cornerRectTopLeft.origin = CGPointMake(trimRange.origin.x - (cornerRectSize.width / 2),
                                    trimRange.origin.y - (cornerRectSize.height / 2));
    cornerRectPath = [UIBezierPath bezierPathWithRect:cornerRectTopLeft];
    [[UIColor redColor] setFill];
    [cornerRectPath fill];
    
    // 右上
    cornerRectTopRight.size = cornerRectSize;
    cornerRectTopRight.origin = CGPointMake((trimRange.origin.x + trimRange.size.width) - (cornerRectSize.width / 2),
                                    trimRange.origin.y - (cornerRectSize.height / 2));
    cornerRectPath = [UIBezierPath bezierPathWithRect:cornerRectTopRight];
    [[UIColor redColor] setFill];
    [cornerRectPath fill];
    
    // 左下
    cornerRectBottomLeft.size = cornerRectSize;
    cornerRectBottomLeft.origin = CGPointMake(trimRange.origin.x - (cornerRectSize.width / 2),
                                    (trimRange.origin.y + trimRange.size.height) - (cornerRectSize.height / 2));
    cornerRectPath = [UIBezierPath bezierPathWithRect:cornerRectBottomLeft];
    [[UIColor redColor] setFill];
    [cornerRectPath fill];
    
    // 右下
    cornerRectBottomRight.size = cornerRectSize;
    cornerRectBottomRight.origin = CGPointMake((trimRange.origin.x + trimRange.size.width) - (cornerRectSize.width / 2),
                                    (trimRange.origin.y + trimRange.size.height) - (cornerRectSize.height / 2));
    cornerRectPath = [UIBezierPath bezierPathWithRect:cornerRectBottomRight];
    [[UIColor redColor] setFill];
    [cornerRectPath fill];
}

/**
 * タッチ開始
 *
 */
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    lastTouchPoint = [[touches anyObject] locationInView:self];
    
    if (CGRectContainsPoint(cornerRectTopRight, lastTouchPoint)
        || CGRectContainsPoint(cornerRectBottomRight, lastTouchPoint)) {
        
        isTouchedLeftCorner = NO;
        isRangeResizing = YES;
        
    } else if (CGRectContainsPoint(cornerRectTopLeft, lastTouchPoint)
               || CGRectContainsPoint(cornerRectBottomLeft, lastTouchPoint)) {
        
        isTouchedLeftCorner = YES;
        isRangeResizing = YES;
        
    } else if (CGRectContainsPoint(trimRange, lastTouchPoint)) {
        
        isRangeMoving = YES;
    }
}

/**
 * タッチ中
 *
 */
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    CGPoint touchPos = [[touches anyObject] locationInView:self];
    
    if (isRangeResizing) {
        [self resizeTrimmingRectToPoint:touchPos];
        
    } else if (isRangeMoving) {
        [self moveTrimmingRectToPoint:touchPos];
    }
    
    lastTouchPoint = touchPos;
}

/**
 * タッチ終了
 *
 */
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    CGPoint touchPos = [[touches anyObject] locationInView:self];
    
    if (isRangeResizing) {
        [self resizeTrimmingRectToPoint:touchPos];
        
    } else if (isRangeMoving) {
        [self moveTrimmingRectToPoint:touchPos];
    }
    
    isRangeResizing = NO;
    isRangeMoving = NO;
}

/**
 * 切り取り矩形範囲のサイズ変更
 *
 */
- (void)resizeTrimmingRectToPoint:(CGPoint)touchPos
{
    if (![self checkRangeOnBaseView]) {
        [self setNeedsDisplay];
        return;
    }
    
    float offsetX = touchPos.x - lastTouchPoint.x;
    if (isTouchedLeftCorner) {
        offsetX *= -1;
    }
    
    trimRange.origin.x -= offsetX / 2;
    trimRange.origin.y -= offsetX / 2;
    trimRange.size.width += offsetX;
    trimRange.size.height += offsetX;
    
    [self setNeedsDisplay];
}

/**
 * 切り取り矩形範囲の移動
 *
 */
- (void)moveTrimmingRectToPoint:(CGPoint)touchPos
{
    if (![self checkRangeOnBaseView]) {
        [self setNeedsDisplay];
        return;
    }
    
    float offsetX = touchPos.x - lastTouchPoint.x;
    float offsetY = touchPos.y - lastTouchPoint.y;
    
    trimRange.origin.x += offsetX;
    trimRange.origin.y += offsetY;
    
    [self setNeedsDisplay];
}

/**
 * 切り取り矩形範囲がベースのベースのビューをはみ出ないように
 *
 */
- (BOOL)checkRangeOnBaseView
{
    BOOL reslt = YES;
    
    // 最小の大きさ
    if (trimRange.size.width < MIM_EDGE_SIZE) {
        trimRange.size.width = MIM_EDGE_SIZE;
        trimRange.size.height = MIM_EDGE_SIZE;
        reslt = NO;
    }
    // 左にはみ出ないように
    if (trimRange.origin.x < 0) {
        trimRange.origin.x = 0;
        reslt = NO;
    }
    // 上にはみ出ないように
    if (trimRange.origin.y < 0) {
        trimRange.origin.y = 0;
        reslt = NO;
    }
    // 右にはみ出ないように
    if ((trimRange.origin.x + trimRange.size.width) > self.frame.size.width) {
        trimRange.origin.x = self.frame.size.width - trimRange.size.width;
        reslt = NO;
    }
    // 下にはみ出ないように
    if ((trimRange.origin.y + trimRange.size.height) > self.frame.size.height) {
        trimRange.origin.y = self.frame.size.height - trimRange.size.height;
        reslt = NO;
    }
    
    return reslt;
}

@end