common/viz.py

import numpy as np
import seaborn as sns
import matplotlib
import matplotlib.pyplot as plt
from pathlib import Path
from typing import Dict, Any, Optional, Tuple, List, Union


def plot_images(
    imgs: List[np.ndarray],
    titles: Optional[List[str]] = None,
    cmaps: Union[str, List[str]] = "gray",
    dpi: int = 100,
    size: Optional[int] = 5,
    pad: float = 0.5,
) -> plt.Figure:
    """Plot a set of images horizontally.
    Args:
        imgs: a list of NumPy or PyTorch images, RGB (H, W, 3) or mono (H, W).
        titles: a list of strings, as titles for each image.
        cmaps: colormaps for monochrome images. If a single string is given,
            it is used for all images.
        dpi: DPI of the figure.
        size: figure size in inches (width). If not provided, the figure
            size is determined automatically.
        pad: padding between subplots, in inches.
    Returns:
        The created figure.
    """
    n = len(imgs)
    if not isinstance(cmaps, list):
        cmaps = [cmaps] * n
    figsize = (size * n, size * 6 / 5) if size is not None else None
    fig, ax = plt.subplots(1, n, figsize=figsize, dpi=dpi)

    if n == 1:
        ax = [ax]
    for i in range(n):
        ax[i].imshow(imgs[i], cmap=plt.get_cmap(cmaps[i]))
        ax[i].get_yaxis().set_ticks([])
        ax[i].get_xaxis().set_ticks([])
        ax[i].set_axis_off()
        for spine in ax[i].spines.values():  # remove frame
            spine.set_visible(False)
        if titles:
            ax[i].set_title(titles[i])
    fig.tight_layout(pad=pad)
    return fig


def plot_color_line_matches(
    lines: List[np.ndarray],
    correct_matches: Optional[np.ndarray] = None,
    lw: float = 2.0,
    indices: Tuple[int, int] = (0, 1),
) -> matplotlib.figure.Figure:
    """Plot line matches for existing images with multiple colors.

    Args:
        lines: List of ndarrays of size (N, 2, 2) representing line segments.
        correct_matches: Optional bool array of size (N,) indicating correct
            matches. If not None, display wrong matches with a low alpha.
        lw: Line width as float pixels.
        indices: Indices of the images to draw the matches on.

    Returns:
        The modified matplotlib figure.
    """
    n_lines = lines[0].shape[0]
    colors = sns.color_palette("husl", n_colors=n_lines)
    np.random.shuffle(colors)
    alphas = np.ones(n_lines)
    if correct_matches is not None:
        alphas[~np.array(correct_matches)] = 0.2

    fig = plt.gcf()
    ax = typing.cast(List[matplotlib.axes.Axes], fig.axes)
    assert len(ax) > max(indices)
    axes = [ax[i] for i in indices]
    fig.canvas.draw()

    # Plot the lines
    for a, l in zip(axes, lines):
        # Transform the points into the figure coordinate system
        transFigure = fig.transFigure.inverted()
        endpoint0 = transFigure.transform(a.transData.transform(l[:, 0]))
        endpoint1 = transFigure.transform(a.transData.transform(l[:, 1]))
        fig.lines += [
            matplotlib.lines.Line2D(
                (endpoint0[i, 0], endpoint1[i, 0]),
                (endpoint0[i, 1], endpoint1[i, 1]),
                zorder=1,
                transform=fig.transFigure,
                c=colors[i],
                alpha=alphas[i],
                linewidth=lw,
            )
            for i in range(n_lines)
        ]

    return fig


def make_matching_figure(
    img0: np.ndarray,
    img1: np.ndarray,
    mkpts0: np.ndarray,
    mkpts1: np.ndarray,
    color: np.ndarray,
    titles: Optional[List[str]] = None,
    kpts0: Optional[np.ndarray] = None,
    kpts1: Optional[np.ndarray] = None,
    text: List[str] = [],
    dpi: int = 75,
    path: Optional[Path] = None,
    pad: float = 0.0,
) -> Optional[plt.Figure]:
    """Draw image pair with matches.

    Args:
        img0: image0 as HxWx3 numpy array.
        img1: image1 as HxWx3 numpy array.
        mkpts0: matched points in image0 as Nx2 numpy array.
        mkpts1: matched points in image1 as Nx2 numpy array.
        color: colors for the matches as Nx4 numpy array.
        titles: titles for the two subplots.
        kpts0: keypoints in image0 as Kx2 numpy array.
        kpts1: keypoints in image1 as Kx2 numpy array.
        text: list of strings to display in the top-left corner of the image.
        dpi: dots per inch of the saved figure.
        path: if not None, save the figure to this path.
        pad: padding around the image as a fraction of the image size.

    Returns:
        The matplotlib Figure object if path is None.
    """
    # draw image pair
    fig, axes = plt.subplots(1, 2, figsize=(10, 6), dpi=dpi)
    axes[0].imshow(img0)  # , cmap='gray')
    axes[1].imshow(img1)  # , cmap='gray')
    for i in range(2):  # clear all frames
        axes[i].get_yaxis().set_ticks([])
        axes[i].get_xaxis().set_ticks([])
        for spine in axes[i].spines.values():
            spine.set_visible(False)
        if titles is not None:
            axes[i].set_title(titles[i])

    plt.tight_layout(pad=pad)

    if kpts0 is not None:
        assert kpts1 is not None
        axes[0].scatter(kpts0[:, 0], kpts0[:, 1], c="w", s=5)
        axes[1].scatter(kpts1[:, 0], kpts1[:, 1], c="w", s=5)

    # draw matches
    if mkpts0.shape[0] != 0 and mkpts1.shape[0] != 0:
        fig.canvas.draw()
        transFigure = fig.transFigure.inverted()
        fkpts0 = transFigure.transform(axes[0].transData.transform(mkpts0))
        fkpts1 = transFigure.transform(axes[1].transData.transform(mkpts1))
        fig.lines = [
            matplotlib.lines.Line2D(
                (fkpts0[i, 0], fkpts1[i, 0]),
                (fkpts0[i, 1], fkpts1[i, 1]),
                transform=fig.transFigure,
                c=color[i],
                linewidth=2,
            )
            for i in range(len(mkpts0))
        ]

        # freeze the axes to prevent the transform to change
        axes[0].autoscale(enable=False)
        axes[1].autoscale(enable=False)

        axes[0].scatter(mkpts0[:, 0], mkpts0[:, 1], c=color[..., :3], s=4)
        axes[1].scatter(mkpts1[:, 0], mkpts1[:, 1], c=color[..., :3], s=4)

    # put txts
    txt_color = "k" if img0[:100, :200].mean() > 200 else "w"
    fig.text(
        0.01,
        0.99,
        "\n".join(text),
        transform=fig.axes[0].transAxes,
        fontsize=15,
        va="top",
        ha="left",
        color=txt_color,
    )

    # save or return figure
    if path:
        plt.savefig(str(path), bbox_inches="tight", pad_inches=0)
        plt.close()
    else:
        return fig


def error_colormap(
    err: np.ndarray, thr: float, alpha: float = 1.0
) -> np.ndarray:
    """
    Create a colormap based on the error values.

    Args:
        err: Error values as a numpy array of shape (N,).
        thr: Threshold value for the error.
        alpha: Alpha value for the colormap, between 0 and 1.

    Returns:
        Colormap as a numpy array of shape (N, 4) with values in [0, 1].
    """
    assert alpha <= 1.0 and alpha > 0, f"Invaid alpha value: {alpha}"
    x = 1 - np.clip(err / (thr * 2), 0, 1)
    return np.clip(
        np.stack(
            [2 - x * 2, x * 2, np.zeros_like(x), np.ones_like(x) * alpha], -1
        ),
        0,
        1,
    )


np.random.seed(1995)
color_map = np.arange(100)
np.random.shuffle(color_map)


def fig2im(fig: matplotlib.figure.Figure) -> np.ndarray:
    """
    Convert a matplotlib figure to a numpy array with RGB values.

    Args:
        fig: A matplotlib figure.

    Returns:
        A numpy array with shape (height, width, 3) and dtype uint8 containing
        the RGB values of the figure.
    """
    fig.canvas.draw()
    (width, height) = fig.canvas.get_width_height()
    buf_ndarray = np.frombuffer(fig.canvas.tostring_rgb(), dtype="u1")
    return buf_ndarray.reshape(height, width, 3)


def draw_matches(
    mkpts0: List[np.ndarray],
    mkpts1: List[np.ndarray],
    img0: np.ndarray,
    img1: np.ndarray,
    conf: np.ndarray,
    titles: Optional[List[str]] = None,
    dpi: int = 150,
    path: Optional[str] = None,
    pad: float = 0.5,
) -> np.ndarray:
    """
    Draw matches between two images.

    Args:
        mkpts0: List of matches from the first image, with shape (N, 2)
        mkpts1: List of matches from the second image, with shape (N, 2)
        img0: First image, with shape (H, W, 3)
        img1: Second image, with shape (H, W, 3)
        conf: Confidence values for the matches, with shape (N,)
        titles: Optional list of title strings for the plot
        dpi: DPI for the saved image
        path: Optional path to save the image to. If None, the image is not saved.
        pad: Padding between subplots

    Returns:
        The figure as a numpy array with shape (height, width, 3) and dtype uint8
        containing the RGB values of the figure.
    """
    thr = 5e-4
    thr = 0.5
    color = error_colormap(conf, thr, alpha=0.1)
    text = [
        "image name",
        f"#Matches: {len(mkpts0)}",
    ]
    if path:
        fig2im(
            make_matching_figure(
                img0,
                img1,
                mkpts0,
                mkpts1,
                color,
                titles=titles,
                text=text,
                path=path,
                dpi=dpi,
                pad=pad,
            )
        )
    else:
        return fig2im(
            make_matching_figure(
                img0,
                img1,
                mkpts0,
                mkpts1,
                color,
                titles=titles,
                text=text,
                pad=pad,
                dpi=dpi,
            )
        )


def draw_image_pairs(
    img0: np.ndarray,
    img1: np.ndarray,
    text: List[str] = [],
    dpi: int = 75,
    path: Optional[str] = None,
    pad: float = 0.5,
) -> np.ndarray:
    """Draw image pair horizontally.

    Args:
        img0: First image, with shape (H, W, 3)
        img1: Second image, with shape (H, W, 3)
        text: List of strings to print. Each string is a new line.
        dpi: DPI of the figure.
        path: Path to save the image to. If None, the image is not saved and
            the function returns the figure as a numpy array with shape
            (height, width, 3) and dtype uint8 containing the RGB values of the
            figure.
        pad: Padding between subplots

    Returns:
        The figure as a numpy array with shape (height, width, 3) and dtype uint8
        containing the RGB values of the figure, or None if path is not None.
    """
    # draw image pair
    fig, axes = plt.subplots(1, 2, figsize=(10, 6), dpi=dpi)
    axes[0].imshow(img0)  # , cmap='gray')
    axes[1].imshow(img1)  # , cmap='gray')
    for i in range(2):  # clear all frames
        axes[i].get_yaxis().set_ticks([])
        axes[i].get_xaxis().set_ticks([])
        for spine in axes[i].spines.values():
            spine.set_visible(False)
    plt.tight_layout(pad=pad)

    # put txts
    txt_color = "k" if img0[:100, :200].mean() > 200 else "w"
    fig.text(
        0.01,
        0.99,
        "\n".join(text),
        transform=fig.axes[0].transAxes,
        fontsize=15,
        va="top",
        ha="left",
        color=txt_color,
    )

    # save or return figure
    if path:
        plt.savefig(str(path), bbox_inches="tight", pad_inches=0)
        plt.close()
    else:
        return fig2im(fig)