import sys
import math
from PyQt5.QtGui import QPixmap, QColor
from PyQt5.QtCore import *
from PyQt5.QtWidgets import QWidget, QDesktopWidget, QApplication, QLabel, QFileDialog, QPushButton, QSlider


class Colors(QWidget):

def __init__(self):
    super().__init__()
    self.img = ''
    self.label = QLabel(self.window())
    self.label.resize(670, 500)
    self.label.move(25, 25)
    self.pixmap = QPixmap()
    self.init_ui()

def init_ui(self):
    self.resize(1200, 900)
    self.center()
    self.setWindowTitle('Center')

    self.h_label = QLabel('H', self)
    self.h_label.move(30, 716)
    self.h_sld = QSlider(Qt.Horizontal, self)
    self.h_sld.setRange(0, 360)
    self.h_sld.setPageStep(1)
    self.h_sld.move(50, 700)
    self.h_sld.resize(500, 50)

    self.s_label = QLabel('S', self)
    self.s_label.move(30, 736)
    self.s_sld = QSlider(Qt.Horizontal, self)
    self.s_sld.setRange(0, 100)
    self.s_sld.setPageStep(1)
    self.s_sld.move(50, 720)
    self.s_sld.resize(500, 50)

    self.v_label = QLabel('V', self)
    self.v_label.move(30, 756)
    self.v_sld = QSlider(Qt.Horizontal, self)
    self.v_sld.setRange(0, 100)
    self.v_sld.setPageStep(1)
    self.v_sld.move(50, 740)
    self.v_sld.resize(500, 50)

    choose_img = QPushButton('Открыть', self)
    choose_img.move(700, 50)
    choose_img.clicked.connect(self.open_on_click)

    save_img = QPushButton('Сохранить', self)
    save_img.move(800, 50)
    save_img.clicked.connect(self.save_on_click)

    to_grey = QPushButton('RGB -> Grey', self)
    to_grey.move(700, 85)
    to_grey.clicked.connect(self.to_grey_on_click)

    to_red = QPushButton('RGB -> Red', self)
    to_red.move(800, 85)
    to_red.clicked.connect(self.to_red_on_click)

    to_green = QPushButton('RGB -> Green', self)
    to_green.move(700, 120)
    to_green.clicked.connect(self.to_green_on_click)

    to_blue = QPushButton('RGB -> Blue', self)
    to_blue.move(800, 120)
    to_blue.clicked.connect(self.to_blue_on_click)

    to_hsv = QPushButton('To HSV', self)
    to_hsv.move(700, 730)
    to_hsv.clicked.connect(self.to_hsv)


    self.show()


def to_grey_on_click(self):
    img = self.pixmap.toImage()
    for x in range(img.width()):
        for y in range(img.height()):
            r = QColor(img.pixel(x, y)).red()
            g = QColor(img.pixel(x, y)).green()
            b = QColor(img.pixel(x, y)).blue()
            a = (0.2126 * r + 0.7152 * g + 0.0722 * b)
            img.setPixel(x, y, QColor(a, a, a).rgb())
    self.label.setPixmap(QPixmap(img))
    self.show()

def to_red_on_click(self):
    img = self.pixmap.toImage()
    for x in range(img.width()):
        for y in range(img.height()):
            r = QColor(img.pixel(x, y)).red()
            img.setPixel(x, y, QColor(r, 0, 0).rgb())
    self.label.setPixmap(QPixmap(img))
    self.show()

def to_green_on_click(self):
    img = self.pixmap.toImage()
    for x in range(img.width()):
        for y in range(img.height()):
            g = QColor(img.pixel(x, y)).green()
            img.setPixel(x, y, QColor(0, g, 0).rgb())
    self.label.setPixmap(QPixmap(img))
    self.show()

def to_blue_on_click(self):
    img = self.pixmap.toImage()
    for x in range(img.width()):
        for y in range(img.height()):
            b = QColor(img.pixel(x, y)).blue()
            img.setPixel(x, y, QColor(0, 0, b).rgb())
    self.label.setPixmap(QPixmap(img))
    self.show()

def open_file_name_dialog(self):
    options = QFileDialog.Options()
    options |= QFileDialog.DontUseNativeDialog
    filename, _ = QFileDialog.getOpenFileName(self, "QFileDialog.getOpenFileName()", "",
                                              "Images (*.jpg *.jpeg *.png)", options=options)
    if filename:
        self.pixmap = QPixmap(filename).scaled(670, 500)

def to_hsv(self):
    self.hsv()

def hsv(self):
    img = self.pixmap.toImage()
    for x in range(img.width()):
        for y in range(img.height()):
            r = QColor(img.pixel(x, y)).red()
            g = QColor(img.pixel(x, y)).green()
            b = QColor(img.pixel(x, y)).blue()
            h, s, v = self.rgb2hsv(r, g, b)
            dh = self.h_sld.value()
            ds = self.s_sld.value() * 0.01
            dv = self.v_sld.value() * 0.01
            h1 = (h + dh) % 360
            s1 = max(min(s + ds, 1), 0)
            v1 = max(min(v + dv, 1), 0)
            r1, g1, b1 = self.hsv2rgb(h1, s1, v1)
            img.setPixel(x, y, QColor(r1, g1, b1).rgb())
    self.label.setPixmap(QPixmap(img))
    self.show()

def rgb2hsv(self, r, g, b):
    r, g, b = r / 255.0, g / 255.0, b / 255.0
    mx = max(r, g, b)
    mn = min(r, g, b)
    df = mx - mn
    if mx == mn:
        h = 0
    elif mx == r:
        h = (60 * ((g - b) / df) + 360) % 360
    elif mx == g:
        h = (60 * ((b - r) / df) + 120) % 360
    elif mx == b:
        h = (60 * ((r - g) / df) + 240) % 360
    if mx == 0:
        s = 0
    else:
        s = df / mx
    v = mx
    return h, s, v

def hsv2rgb(self, h, s, v):
    h = float(h)
    s = float(s)
    v = float(v)
    h60 = h / 60.0
    h60f = math.floor(h60)
    hi = int(h60f) % 6
    f = h60 - h60f
    p = v * (1 - s)
    q = v * (1 - f * s)
    t = v * (1 - (1 - f) * s)
    r, g, b = 0, 0, 0
    if hi == 0:
        r, g, b = v, t, p
    elif hi == 1:
        r, g, b = q, v, p
    elif hi == 2:
        r, g, b = p, v, t
    elif hi == 3:
        r, g, b = p, q, v
    elif hi == 4:
        r, g, b = t, p, v
    elif hi == 5:
        r, g, b = v, p, q
    r, g, b = int(r * 255), int(g * 255), int(b * 255)
    return r, g, b

def open_on_click(self):
    self.open_file_name_dialog()
    self.label.setPixmap(self.pixmap)

def save_on_click(self):
    self.save_file_dialog()

def save_file_dialog(self):
    options = QFileDialog.Options()
    options |= QFileDialog.DontUseNativeDialog
    filename, _ = QFileDialog.getSaveFileName(self, "QFileDialog.getSaveFileName()", "",
                                              "Images (*.jpg *.jpeg *.png)", options=options)
    if filename:
        self.label.pixmap().save(filename)

def center(self):
    qr = self.frameGeometry()
    cp = QDesktopWidget().availableGeometry().center()
    qr.moveCenter(cp)
    self.move(qr.topLeft())


if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Colors()
    sys.exit(app.exec_())

#!/usr/bin/env python3
"""Usage: to-grey <image>"""
import sys
from PyQt5.Qt import QApplication, QColor, QIcon, QPixmap, QSize, QToolButton

def on_click():
    img = w.icon().pixmap(qsize).toImage()
    for x in range(img.width()):
        for y in range(img.height()):
            r = QColor(img.pixel(x, y)).red()
            g = QColor(img.pixel(x, y)).green()
            b = QColor(img.pixel(x, y)).blue()
            a = (0.2126 * r + 0.7152 * g + 0.0722 * b)
            img.setPixel(x, y, QColor(a, a, a).rgb())
    w.setIcon(QIcon(QPixmap(img)))

app = QApplication(sys.argv)
if len(app.arguments()) != 2:
    sys.exit(__doc__)
w = QToolButton()
w.setIcon(QIcon(app.arguments()[1]))
qsize = QSize(300, 300)
w.setIconSize(qsize)
w.clicked.connect(on_click)
# center
w.adjustSize()  # update w.rect() now
w.move(app.desktop().screen().rect().center() - w.rect().center())
w.show()
sys.exit(app.exec_())

$ python3 to-gray.py ~/Pictures/example.jpg

$ python -mprofile --sort cumtime to-gray.py ~/Pictures/example.jpg

$ pip install pprofile
$ pprofile --exclude-syspath to-gray.py ~/Pictures/example.jpg

#!/usr/bin/env python3
"""Usage: to-grey <image>"""
import sys
import numpy as np         # $ pip install numpy
from PyQt5.Qt import QApplication, QIcon, QImage, QPixmap, QSize, QToolButton

def on_click():
    # r = arr[..., 0]
    # g = arr[..., 1]
    # b = arr[..., 2]
    # a = (0.2126 * r + 0.7152 * g + 0.0722 * b)
    a = arr @ [0.2126, 0.7152, 0.0722]  # np.dot
    # arr[..., 0] = a
    # arr[..., 1] = a
    # arr[..., 2] = a
    arr[...] = a[..., np.newaxis]

    w.setIcon(QIcon(QPixmap(qimage)))

app = QApplication(sys.argv)
if len(app.arguments()) != 2:
    sys.exit(__doc__)
w = QToolButton()
qimage = QImage(app.arguments()[1]).convertToFormat(QImage.Format_RGB888)
w.setIcon(QIcon(QPixmap(qimage)))
width, height = qimage.width(), qimage.height()
w.setIconSize(QSize(width, height))
ptr = qimage.bits()
ptr.setsize(qimage.byteCount())
arr = np.ndarray((width, height, 3),
                 dtype=np.uint8, buffer=ptr)  # share data
w.clicked.connect(on_click)
# center
w.adjustSize()  # update w.rect() now
w.move(app.desktop().screen().rect().center() - w.rect().center())
w.show()
sys.exit(app.exec_())

def rgb2gray_rgb(arr):
    a = arr @ [0.2126, 0.7152, 0.0722]
    arr[...] = a[..., np.newaxis]