====== Compare ======

===== Usage =====
Compares images with a given metric if the number of images in the two inputs match. A 1 to -1 comparison will be performed. If the numbers dont match every images in input 1 will be compared to every image in input 2. Thereby the number of images in input 1 needs to be bigger number of images in input 2. 

===== Parameters and I/O =====
Different modes for comparing images can be chosen.

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^ Modes                 ^ Description     ^
| CCC  | Cross Correlation Coefficient is used as metric. **normalize:** enables normalization of the images before calculation. This should be done if the images are not normalized up to here! **radius:** radius of a centered circular mask which is used before comparing the images. If the value is 0 no mask is used.   |
| covariance | Correlation Variance Ratio of the images |
| Fourier ring correlation | Fourier Ring Correlation of the images is used as comparison metric  |  
| normalized mean square error | Normalized mean square error is used as comparison metric |
| sum of absolute differences  | Sum of Absolute Differences is used as comparison metric |

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^ New/Changed Header Values ^ Description ^
| //ccc-/nmse-/phash-/sad-/frc-/cov-/mui-/pHashPeakHeight//         | Comparison value of the two images from the inputs on that position with chosen metric |
| //ccc-/nmse-/phash-/sad-/frc-/cov-/mui-/pHashPeakReferenceIndex// | ImageID of the image from input2 that gives the highest metric value (only written if number of images in //input1// is bigger than number of images in //input2//) |

===== Additional Information ===== 
  * [[https://en.wikipedia.org/wiki/Cross-correlation|Cross Correlation]]
  * [[https://rem.jrc.ec.europa.eu/RemWeb/atmes2/20b.htm|NMSE]]
  * [[https://en.wikipedia.org/wiki/Sum_of_absolute_differences|SAD]]
  * [[https://en.wikipedia.org/wiki/Fourier_shell_correlation|Fourier Ring Correlation]]
  * [[https://en.wikipedia.org/wiki/Correlation_ratio|COV]]