自学教程：利用Python实现生成颜色表(color chart)

# -*- coding: utf-8 -*-import cv2import numpy as npdef generate_color_chart(block_num=18,                         block_columns=6,                         grid_width=32,                         grid_height=None):    """    Generate color chart by uniformly distributed color indexes, only support    8 bit (uint8).    Parameters    ----------    block_num: Block number of color chart, also the number of color indexes.    block_columns: Column number of color chart. Row number is computed by        block_num / block_columns    grid_width: Width of color grid    grid_height: Height of color grid. If not set, it will equal to grid_width.    """    color_index = np.linspace(0, 255, block_num)    color_index = np.uint8(np.round(color_index))    if grid_height is None:        grid_height = grid_width    # compute sizes    block_rows = np.int_(np.ceil(block_num / block_columns))    block_width = grid_width * block_num    block_height = grid_height * block_num    width = block_width * block_columns    height = block_height * block_rows    result = np.zeros((height, width, 3), dtype=np.uint8)    # compute red-green block, (blue will be combined afterward)    red_block, green_block = np.meshgrid(color_index, color_index)    red_block = expand_pixel_to_grid(red_block, grid_width, grid_height)    green_block = expand_pixel_to_grid(green_block, grid_width, grid_height)    rg_block = np.concatenate([red_block, green_block], axis=2)    # combine blue channel    for i in range(block_num):        blue = np.ones_like(rg_block[..., 0], dtype=np.uint8) * color_index[i]        color_block = np.concatenate([rg_block, blue[..., np.newaxis]], axis=2)        # compute block index        block_row = i // block_columns        block_column = i % block_columns        xmin = block_column * block_width        ymin = block_row * block_height        xmax = xmin + block_width        ymax = ymin + block_height        result[ymin:ymax, xmin:xmax, :] = color_block    result = result[..., ::-1]  # convert from rgb to bgr    return resultdef expand_pixel_to_grid(matrix, grid_width, grid_height):    """    Expand a pixel to a grid. Inside the grid, every pixel have the same value    as the source pixel.    Parameters    ----------    matrix: 2D numpy array    grid_width: width of grid    grid_height: height of grid    """    height, width = matrix.shape[:2]    new_heigt = height * grid_height    new_width = width * grid_width    repeat_num = grid_width * grid_height    matrix = np.expand_dims(matrix, axis=2).repeat(repeat_num, axis=2)    matrix = np.reshape(matrix, (height, width, grid_height, grid_width))    # put `height` and `grid_height` axes together;    # put `width` and `grid_width` axes together.    matrix = np.transpose(matrix, (0, 2, 1, 3))    matrix = np.reshape(matrix, (new_heigt, new_width, 1))    return matrixif __name__ == '__main__':    color_chart16 = generate_color_chart(block_num=16,                                         grid_width=32,                                         block_columns=4)    color_chart18 = generate_color_chart(block_num=18,                                         grid_width=32,                                         block_columns=6)    color_chart36 = generate_color_chart(block_num=36,                                         grid_width=16,                                         block_columns=6)    color_chart52 = generate_color_chart(block_num=52,                                         grid_width=8,                                         block_columns=13)    color_chart256 = generate_color_chart(block_num=256,                                          grid_width=1,                                          block_columns=16)    cv2.imwrite('color_chart16.png', color_chart16)    cv2.imwrite('color_chart18.png', color_chart18)    cv2.imwrite('color_chart36.png', color_chart36)    cv2.imwrite('color_chart52.png', color_chart52)    cv2.imwrite('color_chart256.png', color_chart256)

# -*- coding: utf-8 -*-import cv2import numpy as npdef generate_color_band(left_colors, right_colors, grade=256, height=32):    """    Generate color bands by uniformly changing from left colors to right    colors. Note that there might be multiple bands.    Parameters    ----------    left_colors: Left colors of the color bands.    right_colors: Right colors of the color bands.    grade: how many colors are contained in one color band.    height: height of one color band.    """    # check and process color parameters, which should be 2D list    # after processing    if not isinstance(left_colors, (tuple, list)):        left_colors = [left_colors]    if not isinstance(right_colors, (tuple, list)):        right_colors = [right_colors]    if not isinstance(left_colors[0], (tuple, list)):        left_colors = [left_colors]    if not isinstance(right_colors[0], (tuple, list)):        right_colors = [right_colors]    # initialize channel, and all other colors should have the same channel    channel = len(left_colors[0])    band_num = len(left_colors)    result = []    for i in range(band_num):        left_color = left_colors[i]        right_color = right_colors[i]        if len(left_color) != channel or len(right_color) != channel:            raise ValueError("All colors should have same channel number")        color_band = np.linspace(left_color, right_color, grade)        color_band = np.expand_dims(color_band, axis=0)        color_band = np.repeat(color_band, repeats=height, axis=0)        color_band = np.clip(np.round(color_band), 0, 255).astype(np.uint8)        result.append(color_band)    result = np.concatenate(result, axis=0)    result = np.squeeze(result)    return resultif __name__ == '__main__':    black = [0, 0, 0]    white = [255, 255, 255]    red = [0, 0, 255]    green = [0, 255, 0]    blue = [255, 0, 0]    gray_band = generate_color_band([[0], [255]], [[255], [0]])    color_band8 = generate_color_band(        [black, white, red, green, blue, black, black, black],        [white, black, white, white, white, red, green, blue]    )    cv2.imwrite('gray_band.png', gray_band)    cv2.imwrite('color_band8.png', color_band8)