understanding difference ratios

[Tim Harrison]

Hello.  Could someone help me understand the difference ratios?  I'm using "Get visual similarity between two images" via the isk-daemon.  I'm using all default isk-daemon settings.

I've imported 3 images which are all very similar with slight differences.

Here are the values I get when comparing images 1, 2, and 3:

1:1 => -38.460000321269035

1:2 => -23.033164676530546

1:3 => -23.0329310612669

2:3 => -40.4697667113698

2:2 => -40.47000032663345

3:3 => -40.47000032663345

These values do not really mean anything to me.  I'm surprised that identity tests reveal different values for different images.  But maybe I'm just misunderstanding what they're being compared to?

Any help would be appreciated.

Thanks,

-Tim

[Ricardo Niederberger Cabral]

Hi Tim. One value alone doesn't mean much. These should be compared against each other. 

The smaller the value between two images is (i.e. the more negative the value is), the more similar the 2 images are.

In your example, images 2 and 3 are more similar to each other than they are to image 1.

Comparing one image against itself is a degenerate case and the value returned should be ignored.

Best regards,

Ricardo Niederberger Cabral
http://www.imgseek.net/
ricardo.cabral at imgseek.net

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