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SynthShapes.blending

Overview

The SynthShapes.blending module offers simple tools for combining multiple shapes, textures, or regions within an image to create seamless and realistic synthetic data. This module is ideal for applications that require simple to complex image compositions.

Blender 

Blender(alpha=cc.Uniform(0.5, 5), intensity_shift=10)

Bases: Module

An nn.Module for alpha blending ROIs of two tensors within a specified ROI mask, and according to the blending parameter alpha.

Diagram

    flowchart TB
        subgraph Inputs
            foreground[Foreground Tensor]
            background[Background Tensor]
            mask[Mask: ROIs to blend]
        end
        foreground --standardize(μ=0, σ=1)--> standardized_foreground
        mask --> masked_shifting
        background --standardize(μ=0, σ=1)--> standardized_background
        standardized_foreground --> masked_shifting
        masked_shifting(Shift Foreground ROIs: add offset to masked
        elements in standardized foreground) --> shifted_rois
        shifted_rois["Shifted Foreground ROIs"] --> blender_function
        standardized_background --> blender_function
        blender_function("Blender Function: alpha blend ROIs") -->
        output[Output: Blended Tensor]
PARAMETER DESCRIPTION
alpha

Blending factor or sampler.

TYPE: Sampler or float DEFAULT: Uniform(0.5, 5)

intensity_shift

Intensity offset WRT mean=0, std=0 background.

TYPE: float DEFAULT: 10

Source code in SynthShapes/blending.py 
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def __init__(
    self,
    alpha: float = cc.Uniform(0.5, 5),
    intensity_shift: float = 10
):
    """
    Parameters
    ----------
    alpha : Sampler or float
        Blending factor or sampler.
    intensity_shift: Sampler or float
        Intensity offset WRT mean=0, std=0 background.
    """
    super(Blender, self).__init__()
    self.alpha = cc.Uniform.make(make_range(0, alpha))
    self.intensity_shift = cc.Uniform.make(make_range(0, intensity_shift))

forward 

forward(foreground, background, mask)

Forward pass of Blender to apply the blending operation and return the blended tensor.

PARAMETER DESCRIPTION
foreground

The tensor with shapes to blend (each shape should have a unique ID).

TYPE: tensor

background

The intensity image (tensor) to blend shapes into.

TYPE: tensor

Source code in SynthShapes/blending.py 
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def forward(
    self,
    foreground: torch.Tensor,
    background: torch.Tensor,
    mask: torch.Tensor
):
    """
    Forward pass of `Blender` to apply the blending operation and return
    the blended tensor.

    Parameters
    ----------
    foreground : tensor
        The tensor with shapes to blend (each shape should have a unique
        ID).
    background : tensor
        The intensity image (tensor) to blend shapes into.
    """
    # Sample params
    alpha = self.alpha()
    intensity_shift = self.intensity_shift()
    # Ensure image and shapes are both float
    foreground = foreground.float()
    background = background.float()
    # Background mean=0, std=1
    background -= background.mean()
    background /= background.std()
    # Foreground mean=0, std=1
    foreground[mask] -= foreground[mask].mean()
    foreground[mask] /= foreground[mask].std()
    foreground[mask] += intensity_shift
    # Perform blending operation
    foreground[mask] = (
        (background[mask] * (1 - alpha))
        + (foreground[mask] * alpha)
    )
    foreground[~mask] = background[~mask]
    return foreground