Matplotlib.colors.rgb_to_hsv() in Python

Matplotlib is an amazing visualization library in Python for 2D plots of arrays. Matplotlib is a multi-platform data visualization library built on NumPy arrays and designed to work with the broader SciPy stack.

matplotlib.colors.rgb_to_hsv()

The matplotlib.colors.rgb_to_hsv() function belongs to the matplotlib.colors module. The matplotlib.colors.rgb_to_hsv() function is used to convert float rgb in the range of 0 to 1 into a numpy array of hsv values.

Syntax: matplotlib.colors.rgb_to_hsv(arr)

Parameters:

• arr: It is an array-like argument in the form of (…, 3) where all values must to be in the range of 0 to 1.

Returns:

• hsv: It returns an ndarray in the form of (…, 3) that comprises of colors converted to hsv values within the range of 0 to 1.

Example 1:

import matplotlib.pyplot as plt
import matplotlib.colors as mcolors


# helper function to plot a
# color table
def colortable(colors, title,
               colors_sort = True,
               emptycols=0):

    # cell dimensions
    width = 212
    height = 22
    swatch_width = 48
    margin = 12
    topmargin = 40

    # Sorting colors based on hue,
    # saturation, value and name.
    if colors_sort is True:
        to_hsv = sorted((tuple(mcolors.rgb_to_hsv(mcolors.to_rgb(color))),
                         name)
                        for name, color in colors.items())
        names = [name for hsv, name in to_hsv]
    else:
        names = list(colors)

    length_of_names = len(names)
    length_cols = 4 - emptycols
    length_rows = length_of_names // length_cols + int(length_of_names % length_cols > 0)

    width2 = width * 4 + 2 * margin
    height2 = height * length_rows + margin + topmargin
    dpi = 72

    figure, axes = plt.subplots(figsize=(width2 / dpi, height2 / dpi),
                                dpi=dpi)

    figure.subplots_adjust(margin/width2, margin/height2,
                           (width2-margin)/width2,
                           (height2-topmargin)/height2)

    axes.set_xlim(0, width * 4)
    axes.set_ylim(height * (length_rows-0.5), -height/2.)
    axes.yaxis.set_visible(False)
    axes.xaxis.set_visible(False)
    axes.set_axis_off()
    axes.set_title(title, fontsize=24, loc="left", pad=10)

    for i, name in enumerate(names):
        rows = i % length_rows
        cols = i // length_rows
        y = rows * height

        swatch_start_x = width * cols
        swatch_end_x = width * cols + swatch_width
        text_pos_x = width * cols + swatch_width + 7

        axes.text(text_pos_x, y, name, fontsize=14,
                horizontalalignment='left',
                verticalalignment='center')

        axes.hlines(y, swatch_start_x, swatch_end_x,
                  color=colors[name], linewidth=18)

    return figure

colortable(mcolors.BASE_COLORS, "Base Colors",
                colors_sort=False, emptycols=1)
colortable(mcolors.TABLEAU_COLORS, "Tableau Palette",
                colors_sort=False, emptycols=2)
colortable(mcolors.CSS4_COLORS, "CSS Colors")

plt.show()

Output:

Example 2:

Image Used:

import matplotlib
import matplotlib.pyplot as plt
import matplotlib.image as mpimg


image = mpimg.imread('food.jpeg')
plt.title("Output image")


hsv = matplotlib.colors.rgb_to_hsv(image)
plt.imshow(hsv)

Output: