CIRotateFilter.h

//
//  CIRotateFilter.h
//  Touches
//
//  Created by valvoline on 05/01/16.
//  Copyright © 2016 valvoline. All rights reserved.
//

#import <CoreImage/CoreImage.h>

@interface CIRotateFilter : CIFilter
@property (retain, nonatomic) CIImage *inputImage;
@property (retain, nonatomic) NSNumber *inputDegree;
@end

CIRotateFilter.m

//
//  CIRotateFilter.m
//  Touches
//
//  Created by valvoline on 05/01/16.
//  Copyright © 2016 valvoline. All rights reserved.
//

@import GLKit;

#import "CIRotateFilter.h"

@implementation CIRotateFilter

- (CGFloat)calculateDiagonal
{
    CGRect rect = _inputImage.extent;
    
    CGFloat seuareWidth  = CGRectGetWidth(rect) * CGRectGetWidth(rect);
    CGFloat seuareheight = CGRectGetHeight(rect) * CGRectGetHeight(rect);
    
    return sqrtf( seuareWidth + seuareheight );
}

- (CGFloat)calculateScaleForAngle:(CGFloat)angle
{
    CGFloat minSideLength = MIN(_inputImage.extent.size.width, _inputImage.extent.size.height);
    angle = ABS(angle);
    CGFloat width = (([self calculateDiagonal] - minSideLength) / 45) * angle + minSideLength;
    CGFloat adjustment = 0;
    if(angle <= 22.5)
    {
        adjustment = (angle / 150);
    }
    else
    {
        adjustment = ((45 - angle) / 150);
    }
    CGFloat scale = (width / minSideLength) + adjustment;
    return scale;
}

- (CIImage *) outputImage
{
    CGFloat a = _inputDegree.floatValue;
    CGFloat x = _inputImage.extent.size.width/2.0;
    CGFloat y = _inputImage.extent.size.height/2.0;

    CGFloat scale = [self calculateScaleForAngle:GLKMathRadiansToDegrees(a)];
    
    CGAffineTransform transform = CGAffineTransformMakeTranslation(x, y);
    transform = CGAffineTransformRotate(transform, a);
    transform = CGAffineTransformTranslate(transform,-x,-y);


    CGAffineTransform transform2 = CGAffineTransformMakeTranslation(x, y);
    transform2 = CGAffineTransformScale(transform2, scale, scale);
    transform2 = CGAffineTransformTranslate(transform2,-x,-y);

    CGAffineTransform concate   = CGAffineTransformConcat(transform2, transform);

    CIFilter *filterTransform = [CIFilter filterWithName:@"CIAffineTransform"];
    NSValue *rotation = [NSValue valueWithCGAffineTransform:concate];
    [filterTransform setValue:rotation forKey:@"inputTransform"];
    [filterTransform setValue:_inputImage forKey:@"inputImage"];
    
    CGRect extent = [_inputImage extent];
    return [filterTransform.outputImage imageByCroppingToRect:extent];
}

@end