Improve default values of augmenters

[aleju]

This should resolve #315.

[breaking] Most augmenters had previously default values that
made them equivalent to identify functions. Users had to explicitly
change the defaults to proper values in order to "activate"
augmentations. To simplify the usage of the library, the default
values of most augmenters were changed to medium-strength
augmentations. E.g.
Sequential([Affine(), UniformVoronoi(), CoarseDropout()])
should now produce decent augmentations.

A few augmenters were set to always-on, maximum-strength
augmentations. This is the case for:

• Grayscale (always fully grayscales images, use
  Grayscale((0.0, 1.0)) for random strengths)
• RemoveSaturation (same as Grayscale)
• Fliplr (always flips images, use Fliplr(0.5) for 50%
  probability).
• Flipud (same as for Fliplr)
• TotalDropout (always drops everything, use
  TotalDropout(0.1) to drop everything for 10% of all images).
• Invert (always inverts images, use Invert(0.1) to invert
  10% of all images)
• Rot90 (always rotates exactly once by 90 degrees,
  use Rot90((0, 4)) for any rotation)
  These settings seemed to better match user-expectations.
  Such maximum-strength settings however were not chosen for all
  augmenters. Some exceptions where one might expect that are e.g.
  Superpixels (replaces only some superpixels with cellwise average
  colors), UniformVoronoi (also only replaces some cells),
  Sharpen (alpha-blends with variable strength, the same is
  the case for Emboss, EdgeDetect and DirectedEdgeDetect)
  and CLAHE (variable clip limits).

Note: Some of the new default values will cause issues with
non-uint8 inputs.

Note: The defaults for per_channel and keep_size were not
adjusted. It is currently still the default behaviour of all
augmenters to affect all channels in the same way and to resize
their outputs back to the input sizes.

The changes to default values are listed below.

imgaug.arithmetic

• Add
  • value: 0 -> (-20, 20)
• AddElementwise
  • value: 0 -> (-20, 20)
• AdditiveGaussianNoise
  • scale: 0 -> (0, 15)
• AdditiveLaplaceNoise
  • scale: 0 -> (0, 15)
• AdditivePoissonNoise
  • scale: 0 -> (0, 15)
• Multiply
  • mul: 1.0 -> (0.8, 1.2)
• MultiplyElementwise:
  • mul: 1.0 -> (0.8, 1.2)
• Dropout:
  • p: 0.0 -> (0.0, 0.05)
• CoarseDropout:
  • p: 0.0 -> (0.02, 0.1)
  • size_px: None -> (3, 8)
  • min_size: 4 -> 3
  • Default for size_px is only used if neither size_percent
    not size_px is provided by the user.
• CoarseSaltAndPepper:
  • p: 0.0 -> (0.02, 0.1)
  • size_px: None -> (3, 8)
  • min_size: 4 -> 3
  • Default for size_px is only used if neither size_percent
    not size_px is provided by the user.
• CoarseSalt:
  • p: 0.0 -> (0.02, 0.1)
  • size_px: None -> (3, 8)
  • min_size: 4 -> 3
  • Default for size_px is only used if neither size_percent
    not size_px is provided by the user.
• CoarsePepper:
  • p: 0.0 -> (0.02, 0.1)
  • size_px: None -> (3, 8)
  • min_size: 4 -> 3
  • Default for size_px is only used if neither size_percent
    not size_px is provided by the user.
• SaltAndPepper:
  • p: 0.0 -> (0.0, 0.03)
• Salt:
  • p: 0.0 -> (0.0, 0.03)
• Pepper:
  • p: 0.0 -> (0.0, 0.05)
• ImpulseNoise:
  • p: 0.0 -> (0.0, 0.03)
• Invert:
  • p: 0 -> 1
• JpegCompression:
  • compression: 50 -> (0, 100)

imgaug.blend

• BlendAlpha
  • factor: 0 -> (0.0, 1.0)
• BlendAlphaElementwise
  • factor: 0 -> (0.0, 1.0)

imgaug.blur

• GaussianBlur:
  • sigma: 0 -> (0.0, 3.0)
• AverageBlur:
  • k: 1 -> (1, 7)
• MedianBlur:
  • k: 1 -> (1, 7)
• BilateralBlur:
  • d: 1 -> (1, 9)
• MotionBlur:
  • k: 5 -> (3, 7)

imgaug.color

• MultiplyHueAndSaturation:
  • mul_hue: None -> (0.5, 1.5)
  • mul_saturation: None -> (0.0, 1.7)
  • These defaults are only used if the user provided neither
    mul nor mul_hue nor mul_saturation.
• MultiplyHue:
  • mul: (-1.0, 1.0) -> (-3.0, 3.0)
• AddToHueAndSaturation:
  • value_hue: None -> (-40, 40)
  • value_saturation: None -> (-40, 40)
  • These defaults are only used if the user provided neither
    value nor value_hue nor value_saturation.
• Grayscale:
  • alpha: 0 -> 1

imgaug.contrast

• GammaContrast:
  • gamma: 1 -> (0.7, 1.7)
• SigmoidContrast:
  • gain: 10 -> (5, 6)
  • cutoff: 0.5 -> (0.3, 0.6)
• LogContrast:
  • gain: 1 -> (0.4, 1.6)
• LinearContrast:
  • alpha: 1 -> (0.6, 1.4)
• AllChannelsCLAHE:
  • clip_limit: 40 -> (0.1, 8)
  • tile_grid_size_px: 8 -> (3, 12)
• CLAHE:
  • clip_limit: 40 -> (0.1, 8)
  • tile_grid_size_px: 8 -> (3, 12)

convolutional

• Sharpen:
  • alpha: 0 -> (0.0, 0.2)
  • lightness: 1 -> (0.8, 1.2)
• Emboss:
  • alpha: 0 -> (0.0, 1.0)
  • strength: 1 -> (0.25, 1.0)
• EdgeDetect:
  • alpha: 0 -> (0.0, 0.75)
• DirectedEdgeDetect:
  • alpha: 0 -> (0.0, 0.75)

imgaug.flip

• Fliplr:
  • p: 0 -> 1
• Flipud:
  • p: 0 -> 1

imgaug.geometric

• Affine:
  • scale: 1 -> {"x": (0.9, 1.1), "y": (0.9, 1.1)}
  • translate_percent: None -> {"x": (-0.1, 0.1), "y": (-0.1, 0.1)}
  • rotate: 0 -> (-15, 15)
  • shear: 0 -> shear={"x": (-10, 10), "y": (-10, 10)}
  • These defaults are only used if no affine transformation
    parameter was set by the user. Otherwise the not-set
    parameters default again towards the identity function.
• PiecewiseAffine:
  • scale: 0 -> (0.0, 0.04)
  • nb_rows: 4 -> (2, 4)
  • nb_cols: 4 -> (2, 4)
• PerspectiveTransform:
  • scale: 0 -> (0.0, 0.06)
• ElasticTransformation:
  • alpha: 0 -> (0.0, 40.0)
  • sigma: 0 -> (4.0, 8.0)
• Rot90:
  • k: (no default) -> k=1

imgaug.pooling

• AveragePooling:
  • k: (no default) -> (1, 5)
• MaxPooling:
  • k: (no default) -> (1, 5)
• MinPooling:
  • k: (no default) -> (1, 5)
• MedianPooling:
  • k: (no default) -> (1, 5)

imgaug.segmentation

• Superpixels:
  • p_replace: 0.0 -> (0.5, 1.0)
  • n_segments: 100 -> (50, 120)
• UniformVoronoi:
  • n_points: (no default) -> (50, 500)
  • p_replace: 1.0 -> (0.5, 1.0).
• RegularGridVoronoi:
  • n_rows: (no default) -> (10, 30)
  • n_cols: (no default) -> (10, 30)
  • p_drop_points: 0.4 -> (0.0, 0.5)
  • p_replace: 1.0 -> (0.5, 1.0)
• RelativeRegularGridVoronoi: Changed defaults from
  • n_rows_frac: (no default) -> (0.05, 0.15)
  • n_cols_frac: (no default) -> (0.05, 0.15)
  • p_drop_points: 0.4 -> (0.0, 0.5)
  • p_replace: 1.0 -> (0.5, 1.0)

imgaug.size

• CropAndPad:
  • percent: None -> (-0.1, 0.1)
  • This default is only used if the user has provided
    neither px nor percent.
• Pad:
  • percent: None -> (0.0, 0.1)
  • This default is only used if the user has provided
    neither px nor percent.
• Crop:
  • percent: None -> (0.0, 0.1)
  • This default is only used if the user has provided
    neither px nor percent.

[codecov-io]

Codecov Report

Merging #582 into master will increase coverage by 0.12%.
The diff coverage is 95.5%.

@@            Coverage Diff             @@
##           master     #582      +/-   ##
==========================================
+ Coverage   96.48%   96.61%   +0.12%     
==========================================
  Files          40       40              
  Lines       14548    15760    +1212     
==========================================
+ Hits        14036    15225    +1189     
- Misses        512      535      +23