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使用 Python–OpenCV

更改图像的对比度和亮度

原文:https://www.geeksforgeeks.org/使用 python-opencv/ 改变图像的对比度和亮度

改变任何图像的亮度和对比度是每个人对图像做的最基本的事情。这意味着改变图像的每个像素的值,可以通过乘以或除以图像的像素值来实现。在本文中,我们将看到如何使用 OpenCV Python 在漂亮的代码中实现我们的理论,

在开始之前,让我们试着理解一些基本概念,比如,什么是亮度?什么是对比?什么是像素?什么是 OpenCV?

  • 亮度:当调节亮度时,图像内的整个色调范围会相应升高或降低。
  • 对比度:提高对比度调整时,中间色调消除。该图像将具有较高的黑色或黑色和白色百分比,或者具有最少中间色调的高光。
  • 像素:像素通常用于表示计算机显示器或屏幕的显示分辨率。像素越大,图像中的细节越多。
  • OpenCV: OpenCV 是用于计算机视觉、机器学习和图像处理的巨大开源库,现在它在实时操作中发挥着重要作用

议程:学习如何使用 OpenCV 调整图像的亮度和对比度。

要求: OpenCV

安装:

pip install openCV

进场:

  • 导入所需模块。
  • 定义主要功能,定义其中需要的数据。
  • 创建一个函数 brightness_contrast,以创建一个跟踪条来调整亮度和对比度。
  • 创建另一个功能来更改亮度和对比度。
  • 显示原始和编辑过的图像。
  • 用“电子稳定控制”终止程序,或简单地关闭窗口。

让我们逐步实现这个:

第一步:这里我们将加载一个图像并创建一个跟踪条。

语法: imread(文件名):filename(图像文件的名称)。

名称窗口(winname): winname(窗口的名称)。

代码:

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if __name__ == '__main__':
    # The function imread loads an
    # image from the specified file and returns it.
    original = cv2.imread("pic.jpeg")

    # Making another copy of an image.
    img = original.copy()

    # The function namedWindow creates
    # a window that can be used as
    # a placeholder for images.
    cv2.namedWindow('GEEK')

    # The function imshow displays
    # an image in the specified window.
    cv2.imshow('GEEK', original)

    # createTrackbar(trackbarName,
    # windowName, value, count, onChange)
    # Brightness range -255 to 255
    cv2.createTrackbar('Brightness', 'GEEK',
                       255, 2 * 255,
                       BrightnessContrast)

    # Contrast range -127 to 127
    cv2.createTrackbar('Contrast', 'GEEK',
                       127, 2 * 127,
                       BrightnessContrast) 

    BrightnessContrast(0)

# The function waitKey waits for
# a key event infinitely  or for
# delay milliseconds, when it is positive.
cv2.waitKey(0)

第二步:通过调用控制器功能,返回编辑后的图像,之后 imshow()功能将显示受影响的图像。

语法: getTrackbarPos(trackbarname,winname):trackbarname(track bar 的名称),winname(窗口的名称)

代码:

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def BrightnessContrast(brightness=0):

    # getTrackbarPos returns the
    # current position of the specified trackbar.
    brightness = cv2.getTrackbarPos('Brightness',
                                    'GEEK')

    contrast = cv2.getTrackbarPos('Contrast',
                                  'GEEK')

    effect = controller(img,
                        brightness,
                        contrast)

    # The function imshow displays
    # an image in the specified window
    cv2.imshow('Effect', effect)

第三步:控制器功能会根据轨迹球位置控制图像的亮度和对比度,并返回编辑后的图像。

语法:加权(src1、alpha、src2、beta、gamma)

参数:

src1: 第一个输入数组。 阿尔法:(第一阵元素的权重。 src2: 第二个输入数组,大小和通道号与 src1 相同。 β:第二阵元的权重。 伽马:标量加到每个和上。

文字(图像、文字、组织、字体、字体比例、颜色、粗细、线型、底部左侧原点)

img: 图像。 文字:待画文字串。 org: 图像中文本字符串的左下角。 fontFace: 字体类型,参见#HersheyFonts。 字体比例:字体比例因子乘以特定字体的基本大小。 颜色:文字颜色。 粗细:用于绘制文字的线条粗细。 l ineType: 线型。请参见#线型。 左下角原点:为真时,图像数据原点在左下角。否则,它在左上角。

蟒蛇 3

def controller(img, brightness=255, contrast=127):
    brightness = int((brightness - 0) * (255 - (-255)) / (510 - 0) + (-255))

    contrast = int((contrast - 0) * (127 - (-127)) / (254 - 0) + (-127))

    if brightness != 0:

        if brightness > 0:

            shadow = brightness

            max = 255

        else:

            shadow = 0
            max = 255 + brightness

        al_pha = (max - shadow) / 255
        ga_mma = shadow

        # The function addWeighted
        # calculates the weighted sum
        # of two arrays
        cal = cv2.addWeighted(img, al_pha,
                              img, 0, ga_mma)

    else:
        cal = img

    if contrast != 0:
        Alpha = float(131 * (contrast + 127)) / (127 * (131 - contrast))
        Gamma = 127 * (1 - Alpha)

        # The function addWeighted calculates
        # the weighted sum of two arrays
        cal = cv2.addWeighted(cal, Alpha,
                              cal, 0, Gamma)

    # putText renders the specified
    # text string in the image.
    cv2.putText(cal, 'B:{},C:{}'.format(brightness,
                                        contrast),
                (10, 30), cv2.FONT_HERSHEY_SIMPLEX,
                1, (0, 0, 255), 2)

    return cal

以下是全部实现:

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import cv2

def BrightnessContrast(brightness=0):

    # getTrackbarPos returns the current
    # position of the specified trackbar.
    brightness = cv2.getTrackbarPos('Brightness',
                                    'GEEK')

    contrast = cv2.getTrackbarPos('Contrast',
                                  'GEEK')

    effect = controller(img, brightness,
                        contrast)

    # The function imshow displays an image
    # in the specified window
    cv2.imshow('Effect', effect)

def controller(img, brightness=255,
               contrast=127):

    brightness = int((brightness - 0) * (255 - (-255)) / (510 - 0) + (-255))

    contrast = int((contrast - 0) * (127 - (-127)) / (254 - 0) + (-127))

    if brightness != 0:

        if brightness > 0:

            shadow = brightness

            max = 255

        else:

            shadow = 0
            max = 255 + brightness

        al_pha = (max - shadow) / 255
        ga_mma = shadow

        # The function addWeighted calculates
        # the weighted sum of two arrays
        cal = cv2.addWeighted(img, al_pha,
                              img, 0, ga_mma)

    else:
        cal = img

    if contrast != 0:
        Alpha = float(131 * (contrast + 127)) / (127 * (131 - contrast))
        Gamma = 127 * (1 - Alpha)

        # The function addWeighted calculates
        # the weighted sum of two arrays
        cal = cv2.addWeighted(cal, Alpha,
                              cal, 0, Gamma)

    # putText renders the specified text string in the image.
    cv2.putText(cal, 'B:{},C:{}'.format(brightness,
                                        contrast), (10, 30),
                cv2.FONT_HERSHEY_SIMPLEX, 1, (0, 0, 255), 2)

    return cal

if __name__ == '__main__':
    # The function imread loads an image
    # from the specified file and returns it.
    original = cv2.imread("pic.jpeg")

    # Making another copy of an image.
    img = original.copy()

    # The function namedWindow creates a
    # window that can be used as a placeholder
    # for images.
    cv2.namedWindow('GEEK')

    # The function imshow displays an
    # image in the specified window.
    cv2.imshow('GEEK', original)

    # createTrackbar(trackbarName,
    # windowName, value, count, onChange)
     # Brightness range -255 to 255
    cv2.createTrackbar('Brightness',
                       'GEEK', 255, 2 * 255,
                       BrightnessContrast)

    # Contrast range -127 to 127
    cv2.createTrackbar('Contrast', 'GEEK',
                       127, 2 * 127,
                       BrightnessContrast) 

    BrightnessContrast(0)

# The function waitKey waits for
# a key event infinitely  or for delay
# milliseconds, when it is positive.
cv2.waitKey(0)

输出:



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