#!/usr/bin/env python3
# Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.

import matplotlib.pyplot as plt


def image_grid(
    images,
    rows=None,
    cols=None,
    fill: bool = True,
    show_axes: bool = False,
    rgb: bool = True,
):
    """
    A util function for plotting a grid of images.

    Args:
        images: (N, H, W, 4) array of RGBA images
        rows: number of rows in the grid
        cols: number of columns in the grid
        fill: boolean indicating if the space between images should be filled
        show_axes: boolean indicating if the axes of the plots should be visible
        rgb: boolean, If True, only RGB channels are plotted.
            If False, only the alpha channel is plotted.

    Returns:
        None
    """
    if (rows is None) != (cols is None):
        raise ValueError("Specify either both rows and cols or neither.")

    if rows is None:
        rows = len(images)
        cols = 1

    gridspec_kw = {"wspace": 0.0, "hspace": 0.0} if fill else {}
    fig, axarr = plt.subplots(
        rows, cols, gridspec_kw=gridspec_kw, figsize=(15, 9)
    )
    bleed = 0
    fig.subplots_adjust(
        left=bleed, bottom=bleed, right=(1 - bleed), top=(1 - bleed)
    )

    for ax, im in zip(axarr.ravel(), images):
        if rgb:
            # only render RGB channels
            ax.imshow(im[..., :3])
        else:
            # only render Alpha channel
            ax.imshow(im[..., 3])
        if not show_axes:
            ax.set_axis_off()
