ColourLike

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Abstract
Author mg262
Version v1.0
Download Colourlike_v10.zip
Category Levels and Chroma
License GPLv2
Discussion Doom9 Thread

Contents

Description

ColourLike makes a clip look like a 'reference' clip by adjusting each colour channel.
It also has a polar-YUV mode, which as its 3 channels has

1) Y,
2) Length of the UV-vector (saturation)
3) Angle of the UV-vector. (hue)

Currently the angle is not changed by the filter (ie does not change hue).

Be careful to feed the filter with the right kind of histogram... YUV, RGB and Polar-YUV are three different kinds.


  • Note: Documentation below are mostly words of author mg262, but edited from various posts on doom9 and had some text inserted to either clarify or denote usage.
    Edited by StainlessS, on Doom9 Forum


Requirements


Syntax and Parameters

    WriteHistogram(clip,string outputfile, int  "every"=1)
      YV12, RGB32
      Computes histograms for each channel of the clip and stores the results in outputFile.
      If e.g.  every=3 is specified, only every 3rd frame of clip is sampled.
      # Returns original clip (No Constructor)


    #CopyHistogram(string InputFilename, string OutputFilename) 
    #  Copy a histogram ie make duplicate file.
    #  Not Implemented (Implememted in source but commented out) 
    
    
    WritePolarHistogram(clip,string outputfile, int  "every"=1)
      YV12 Only, Emits a "Requires RGB32" message if NOT YV12 ???
      Computes polar histograms for each channel of the clip and stores the results in outputFile.
      If e.g.  every=3 is specified, only every 3rd frame of clip is sampled.
      # Returns original clip (No Constructor)
    
        
    CopyPolarHistogram(string InputFilename, string OutputFilename)
      Copy a Polar histogram ie make duplicate file.
      # Returns 0
    
    
    WriteColourLikeCurve(string OutputFilename, string sourceHistogramFile, string referenceHistogramFile)
      Writes YUV Equalising curves
      # Returns 0
    
    
    ColourLike(clip source,string sourceHistogramFile,string referenceHistogramFile, \
              bool "affectfirst"=true, bool "affectsecond"=true,bool "affectthird"=true)
      YV12, RGB32 
      Takes a clip source and histogram files for this clip and a reference clip, and applies curves to each channel
      chosen, to make source look as much like the reference as possible.
    
      
    PolarColourLike(clip source, string sourceHistogramFile,string referenceHistogramFile, \
           bool "affectfirst"=true, bool "affectsecond"=true,bool "affectthird")
      YV12 Only # RGB32, Not implemented for RGB32 depite error msg saying YV12 & RGB32 only
      Takes a clip source and histogram files for this clip and a reference clip, and applies curves to the clip,
      to make source look as much like the reference as possible.
      affectfirst, affects Y channel
      affectsecond, affects length of the UV-vector (ie SATURATION)
      affectthird, if supplied is IGNORED, (angle of the UV-vector) (ie Does not change HUE)   
      The first true tells the filter to affect luma, and the second true tells it to affect saturation.

  
    ApplyAMP(clip, string CurveFilename)
      YV12, RGB32
      Affects Y channel only for YV12


    SaturationGamma(clip, float gamma, float "fixed"=127.0)
      YV12
      Affects U & V channels Only (applies gamma to length of the UV-vector [SAT])
      Y channel untouched
        I've also added a saturation gamma function. The idea is this. A normal gamma operation can brighten or darken
        midtones while (approximately) leaving highlights and shadows alone. The saturation Gamma can increase or decrease
        the saturation of areas with medium saturation, while leaving greys and very saturated areas alone. 
        The fixed parameter gives a "very saturated" saturation level [measured as a distance from (128,128)] that will
        be left alone by the function... but it will work fine if you leave this number at default.
        The results are (in my view) quite interesting, so do give it a go!


Examples

  Here are some examples from a case where the same clip is present in (unrelated) DVD and VHS sources.

  First generate the histograms:

  dvd.WriteHistogram("dvd hist 100.txt", 100)
  vhs.WriteHistogram("vhs hist 100.txt", 100)

  Then, say, adjust the VHS to look as much like the DVD as possible:
    vhs.colourlike("vhs hist.txt", "dvd hist.txt")
  or 
    vhs.colourlike("vhs hist.txt", "dvd hist.txt", true, false, false)
      which means: just process Y (respectively R) but ignore U and V (respectively G and B).

  Or adjust the DVD to look as much like the VHS as possible
  dvd.colourlike("dvd hist.txt", "vhs hist.txt")

  Polar:
    dvd
    WritePolarHistogram("dvd polar hist 1.txt", 1)
    vhs
    WritePolarHistogram("vhs polar hist 1.txt", 1)
    
    dvd.polarcolourlike("dvd polar hist 1.txt", "vhs polar hist 1.txt", true, true, true) #last 'true' is ignored

      The first true tells the filter to affect luma, and the second true tells it to affect saturation.
      This should in theory change the brightness, contrast, saturation, etc but not affect hue.
      I haven't found this to be very useful in practice.
      I think a variant which changed hue would be more useful, but this is ill-defined... or more precisely, 
      because hue is represented by a circle rather than a line, there is a whole family of 'hue-equalising' filters...


Changelog

Version      Date            Changes
v1.0 2005/08/25 - Latest release


Archived Downloads

Version Download Mirror
v1.0 Colourlike_v10.zip Colourlike_v10.zip


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