//
// Created by Gabriel Handford on 3/1/09.
// Copyright 2009-2013. All rights reserved.
// Created by John Boiles on 10/20/11.
// Copyright (c) 2011. All rights reserved
// Modified by Felix Schulze on 2/11/13.
// Copyright 2013. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
//

#import "UIImage+Compare.h"

@implementation UIImage (Compare)

- (BOOL)compareWithImage:(UIImage *)image
{
NSAssert(CGSizeEqualToSize(self.size, image.size), @"Images must be same size.");

// The images have the equal size, so we could use the smallest amount of bytes because of byte padding
size_t minBytesPerRow = MIN(CGImageGetBytesPerRow(self.CGImage), CGImageGetBytesPerRow(image.CGImage));
size_t referenceImageSizeBytes = CGImageGetHeight(self.CGImage) * minBytesPerRow;
void *referenceImagePixels = calloc(1, referenceImageSizeBytes);
void *imagePixels = calloc(1, referenceImageSizeBytes);

if (!referenceImagePixels || !imagePixels) {
free(referenceImagePixels);
free(imagePixels);
return NO;
}

CGContextRef referenceImageContext = CGBitmapContextCreate(referenceImagePixels,
CGImageGetWidth(self.CGImage),
CGImageGetHeight(self.CGImage),
CGImageGetBitsPerComponent(self.CGImage),
minBytesPerRow,
CGImageGetColorSpace(self.CGImage),
(CGBitmapInfo)kCGImageAlphaPremultipliedLast
);
CGContextRef imageContext = CGBitmapContextCreate(imagePixels,
CGImageGetWidth(image.CGImage),
CGImageGetHeight(image.CGImage),
CGImageGetBitsPerComponent(image.CGImage),
minBytesPerRow,
CGImageGetColorSpace(image.CGImage),
(CGBitmapInfo)kCGImageAlphaPremultipliedLast
);

CGFloat scaleFactor = [UIScreen mainScreen].scale;
CGContextScaleCTM(referenceImageContext, scaleFactor, scaleFactor);
CGContextScaleCTM(imageContext, scaleFactor, scaleFactor);

if (!referenceImageContext || !imageContext) {
CGContextRelease(referenceImageContext);
CGContextRelease(imageContext);
free(referenceImagePixels);
free(imagePixels);
return NO;
}

CGContextDrawImage(referenceImageContext, CGRectMake(0.0f, 0.0f, self.size.width, self.size.height), self.CGImage);
CGContextDrawImage(imageContext, CGRectMake(0.0f, 0.0f, image.size.width, image.size.height), image.CGImage);
CGContextRelease(referenceImageContext);
CGContextRelease(imageContext);

BOOL imageEqual = (memcmp(referenceImagePixels, imagePixels, referenceImageSizeBytes) == 0);
free(referenceImagePixels);
free(imagePixels);
return imageEqual;
}

@end