compare multiple images in ios in objective-C

Question

i am comparing images with each other here is the code for it.

for (int i=0; i<arrImageData.count; i++) { for (int j=i+1; j<arrImageData.count; j++) { if ([arrImageData[i]isEqualToData:arrImageData[j]]) { [arrImages addObject:arrImage[i]]; } } }

now problem is when number of images increase it takes too much time to calculate.is there any better solution for it?

assume there aree 1000 images...so it compare 1st image with other 999 images...after that 2nd image will compare with other 998 image..and so on...so it takes too much time to compute..give me better solution for this issue — Harshit
– Harshit, Commented Dec 16, 2015 at 12:31
yes.. i am comparing nsdata comparison works perfect but it takes time when there is high number of images — Harshit
– Harshit, Commented Dec 16, 2015 at 12:35
this comparison is works when data is exact copy of that data....if i want to do like "if 10% of image is same then it count as same image"..any solution for this?? — Harshit
– Harshit, Commented Dec 16, 2015 at 12:43

Community · Accepted Answer · 2017-05-23 12:31:02Z

1

I think you should use hashes for comparison. Refer this link: Generate hash from UIImage It will help you.

edited May 23, 2017 at 12:31

CommunityBot

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answered Dec 16, 2015 at 12:33

Nilesh

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Community · Accepted Answer · 2017-05-23 11:52:06Z

you should use hashes to compare big amount of data

1 you can compare UImage directrly: image1.hash == image2.hash

2 you can calculate your own hash for each image added to the array, it will be calculated once and used for every comparison

here is the hash algorithm https://en.wikipedia.org/wiki/MD5

PS it will works if image data is absolutely equal, it much more difficult to compare two different images with one "content" Image comparison - fast algorithm

but i am comparing images one by one with each other thats why it takes too much time...anyother algorithm you suggest

Jiri Zachar · Accepted Answer · 2015-12-16 12:34:44Z

0

you can try something like this:

- (BOOL)image:(UIImage *)image1 isEqualTo:(UIImage *)image2{ return [UIImagePNGRepresentation(image1) isEqual:UIImagePNGRepresentation(image2)]; }

answered Dec 16, 2015 at 12:34

Jiri Zachar

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2 Comments

NSNoob Over a year ago

That's what he is doing. He wants to do it faster as he has a large set of images

Harshit Over a year ago

this is the same as i m doing...i want faster method to compare lots of images...

Vidhyanand · Accepted Answer · 2015-12-16 13:55:03Z

You can use Fast Enumeration as Below

 for(UIImage *img in arrImageData) { for (UIImage *comImg in arrImageData) { if ([UIImageJPEGRepresentation(img, 0) isEqual:UIImageJPEGRepresentation(comImg, 0)]) { [arrImages addObject:img]; } } }

Hope it helps you...!

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