colors/losses.py

import torch

from utils import RGBMYC_ANCHOR

# def smoothness_loss(outputs):
#     # Sort outputs for smoothness calculation
#     sorted_outputs, _ = torch.sort(outputs, dim=0)
#     first_elements = sorted_outputs[:2]

#     # Concatenate the first element at the end of the sorted_outputs
#     extended_sorted_outputs = torch.cat((sorted_outputs, first_elements), dim=0)

#     # Calculate smoothness in the sorted outputs
#     first_derivative = torch.diff(extended_sorted_outputs, n=1, dim=0)
#     second_derivative = torch.diff(first_derivative, n=1, dim=0)
#     smoothness_loss = torch.mean(torch.abs(second_derivative))
#     return smoothness_loss


def preservation_loss(inputs, outputs, target_inputs=None, target_outputs=None):
    # Distance Preservation Component (or scaled euclidean if given targets)
    # Encourages the model to keep relative distances from the RGB space in the transformed space
    if target_inputs is None:
        target_inputs = inputs
    else:
        assert target_outputs is not None
    if target_outputs is None:
        target_outputs = outputs

    # Calculate RGB Norm
    max_rgb_distance = torch.sqrt(torch.tensor(2 + 1))  # scale to [0, 1]
    # max_rgb_distance = 1
    rgb_norm = (
        torch.triu(torch.norm(inputs[:, None, :] - target_inputs[None, :, :], dim=-1))
        / max_rgb_distance
    )
    # connect (0, 0, 0) and (1, 1, 1): max_rgb_distance in the RGB space
    # rgb_norm = rgb_norm % 1  # i think this is why yellow and blue end up adjacent.
    # yes it connects black and white, but also complimentary colors to primary
    # print(rgb_norm)

    # Calculate 1D Space Norm (modulo 1 to account for circularity)
    transformed_norm = circle_norm(outputs, target_outputs)  # * 2

    diff = torch.pow(rgb_norm - transformed_norm, 2)
    N = len(outputs)
    N = (N * (N - 1)) / 2
    # N = torch.count_nonzero(rgb_norm)
    return torch.sum(diff) / N


def circle_norm(vector, other_vector):
    # Assumes vectors are of shape (N,1)
    loss_a = torch.triu(torch.abs((vector - other_vector.T)))
    loss_b = torch.triu(1 - torch.abs((vector - other_vector.T)))
    loss = torch.minimum(loss_a, loss_b)
    return loss


def separation_loss(red, green, blue):
    # Separation Component
    # TODO: remove
    # Encourages the model to keep R, G, B values equally separated in the transformed space
    red_loss = torch.abs(0 - red)
    green_loss = torch.abs(1 / 3 - green) / (2 / 3)
    blue_loss = torch.abs(2 / 3 - blue) / (2 / 3)
    return red_loss + green_loss + blue_loss


def calculate_separation_loss(model):
    # TODO: remove
    # Wrapper function to calculate separation loss
    outputs = model(RGBMYC_ANCHOR.to(model.device))
    red, green, blue = outputs[0], outputs[1], outputs[2]
    return separation_loss(red, green, blue)


if __name__ == "__main__":
    # test preservation loss
    # create torch vector containing pure R, G, B.
    test_input = torch.tensor(
        [[1, 0, 0], [0, 1, 0], [0, 0, 1], [0, 0, 0], [1, 1, 1]], dtype=torch.float32
    )
    test_output = torch.tensor([[0], [1 / 3], [2 / 3], [0], [0]], dtype=torch.float32)

    print(preservation_loss(test_input[:3], test_output[:3]))
    rgb = torch.tensor([[0], [1 / 3], [2 / 3]], dtype=torch.float32)
    print(separation_loss(red=rgb[0], green=rgb[1], blue=rgb[2]))