Anaglyph HALD Generator - Configuration Files and Control Parameters

Anahald configuration file contains a set of key=value pairs, where keys are names of control parameters (specs follow), and values are, well, their values. File format is that of commonly used .ini files where the key=value pairs are organized into sections.
Since the Anahald configuration file is utterly straightforward, an example with only a few explanations will suffice.
Here is a sample Anahald configuration file - "ahg_oleg_gp.ini" - one of the four supplied with Anahald:

[Original_User_Specified]
GreenToBlueBiasMultWhenMinor=1.0
MaxBalancedMajorToMaxMinorRatio=2.0
MaxRgbVal=255
MinBndBalancedMajorToMaxMinorRatio=1.3
MinMinorScaleOption=2
PreInflateMinorToFract=1.0
PreSqueezeMajorToFract=0.90
SmoothBndBalancedOption=2
[Secondary]
LowPassFractionWhenMinor=0.00392156862745098
LowPassThreshold=1
MaxBalancedMajorToMinMinorRatio=6.0
MinRgbVal=0
ScaleBoudaryBalanced=1
ZeroSubstRgbValForRatio=0.5

The syntax:

• a line with a string in brackets ([]) starts a section
  
  • only [Original_User_Specified] is of importance
    
    • do not alter anything in [Secondary] section
      
• there should be only one key-value pair in a line
  
• empty lines are permitted
  
• currently there's no support for comments
  
• there should be no whitespace between key, "=" sign, and value
  

That's all one needs to know about Anahald configuration file format.

The detailed and comprehensive explanations on how each control parameter affects color computation is presented in Anahald_Algorithm_and_Parameters.html; this section summarizes the parameters while attempting to explain them from the usage viewpoint.

Here is the full list:

• GreenToBlueBiasMultWhenMinor - floating-point; range: [0.5 … 2.0]
  Defines color-shift on the minor (cyan) side in red-dominated colors
  
  • green channel is multiplied by 'GreenToBlueBiasMultWhenMinor'
    
  • blue channel is divided by 'GreenToBlueBiasMultWhenMinor'
    
  • (e.g. ''GreenToBlueBiasMultWhenMinor' < 1 results in blue cast)
    
• MaxBalancedMajorToMaxMinorRatio - floating-point; range: [1.0 … 6.0]
  Specifies the maximum sides-ratio for the color-trio (RGB) to be considered balanced
  
  • no color in the resulting LUT will have a bigger sides-ratio
    
  • the smaller 'MaxBalancedMajorToMaxMinorRatio', the stronger is the change in colors
    
  • for red-dominated colors, SidesRatio == R / max(G, B)
    
  • for cyan-dominated colors, SidesRatio == max(G, B) / R
    
• MaxRgbVal == 255 - a constant for now; meant for future extensions
  
• MinBndBalancedMajorToMaxMinorRatio; range: [1.0 … MaxBalancedMajorToMaxMinorRatio)
  Defines the lower bound of sides-ratio that could be affected while smoothening the boundary between balanced and unbalanced colors
  
  • colors with sides-ratio smaller than 'MinBndBalancedMajorToMaxMinorRatio' will not be altered for any purpose
    
  • 'MinBndBalancedMajorToMaxMinorRatio' must be strictly smaller than 'MaxBalancedMajorToMaxMinorRatio'
    
• MinMinorScaleOption - two possible values - 1 or 2
  Selects the formula used to balance the smaller (min-minor) of green and blue channels in red-dominated colors
  
  • for example if RGB=(100 30 10), red is major, green is max-minor, blue is min-minor
    
  • =1 -> min-minor channel balanced directly versus the red (major) channel
    
  • =2 -> relative-change of min-minor channel equals to relative-change of the max-minor channel
    
  • apparently, option "2" produces color tints closer to the original, but option "1" sometimes improves visibility of problematic objects
    
• PreInflateMinorToFract - floating-point; range: [0.5 … 1.0]
  If < 1.0, tells to increase the minor-side before further computations, so that the initial sides-ratio becomes 'PreInflateMinorToFract' of its original value
  
  • eventually forces the minor side of the resulting balanced color to be larger than it otherwise would
    
  • in a red-dominated color, green- and blue channels are scaled-up by the same factor; this factor is determined by the max-minor channel
    
• PreSqueezeMajorToFract - floating-point; range: [0.5 … 1.0]
  (symmetrical to PreInflateMinorToFract)
  If < 1.0, tells to decrease the major-side before further computations, so that the initial sides-ratio becomes 'PreSqueezeMajorToFract' of its original value
  
  • eventually forces the minor side of the resulting balanced color to be larger than it otherwise would
    
  • in a cyan-dominated color, green- and blue channels are scaled-down by the same factor; this factor is determined by the max-major channel
    
  • only one of PreInflateMinorToFract or PreSqueezeMajorToFract allowed to be active (e.g. < 1)
    
  • a tip on how to prevent nearly-red colors turning into pink or orange: make PreSqueezeMajorToFract relatively small, so that the balance is achieved by reducing red channel instead of bumping-up blue or green; visually the resulting color ends-up darker, but still appears to the eye as being red
    
• SmoothBndBalancedOption - two possible values - 1 or 2
  Selects the formula used to smoothen the boundary between originally-balanced and originally-unbalanced colors. Otherwise having the former preserved and the latter altered leaves color-gradients that cross this boundary with unwanted "stairs"
  
  • the originally-balanced colors applicable for the change have their sides-ratio between MinBndBalancedMajorToMaxMinorRatio and MaxBalancedMajorToMaxMinorRatio
    
    • such colors are referred to as marginally-balanced
      
  • the ultimate color-channel values will be weighted averages between their original values and the values they would receive if the color was treated as originally-unbalanced:
    
    • channelValueNew = (1 - w) * channelValueOld + w * channelValueIfScaled
      (0.0 <= w <= 1.0)
      amount of change starts with same-as-if-unbalabced (W=1) for colors with sides-ratio of MaxBalancedMajorToMaxMinorRatio, goes down with sides-ratiuo decreasing, and reaches zero (w=0) for colors with sides-ratio of MinBndBalancedMajorToMaxMinorRatio
      
  • the SmoothBndBalancedOption parameter defines how the weighting-factor (w) is calculated:
    
    • =1 -> "linear-smoothening" - the graph of weighting-factor depending on sides-ratio is a straight line from 1 at MaxBalancedMajorToMaxMinorRatio to 0 (zero) at MinBndBalancedMajorToMaxMinorRatio
      
    • =2 -> "parabolic-smoothening" - the graph of weighting-factor depending on sides-ratio is a half-parabola with the vertex (the maximum, upper point) of 1 at MaxBalancedMajorToMaxMinorRatio and touching 0 (zero) at MinBndBalancedMajorToMaxMinorRatio
      
    • "parabolic" option achieves smaller slope at the balanced-unbalanced boundary; this is a must when the range of marginally-balanced colors is rather narrow (MinBndBalancedMajorToMaxMinorRatio comes close to MaxBalancedMajorToMaxMinorRatio)
      
  • an alternative to smoothening the balanced-unbalanced boundary is to choose for each stereopair a LUT made with MaxBalancedMajorToMaxMinorRatio that doesn't create unwanted artifacts
    
    • in order to disable smoothening the boundary, set MinBndBalancedMajorToMaxMinorRatio == MaxBalancedMajorToMaxMinorRatio