python - OpenCV 和 Python : quickly superimpose mask over image without overflow

Question

我想在彩色图像上叠加一个二进制掩码，这样在掩码“打开”的地方，像素值的变化量我可以设置。结果应如下所示:

我正在使用 OpenCV 2.4 和 Python 2.7.6。我有一种方法效果很好，但速度很慢，另一种方法速度很快，但存在上溢和下溢问题。这是更快代码的结果，带有上溢/下溢工件:

这是我的代码，显示了快速版本和慢速版本:

def superimpose_mask_on_image(mask, image, color_delta = [20, -20, -20], slow = False):
    # superimpose mask on image, the color change being controlled by color_delta
    # TODO: currently only works on 3-channel, 8 bit images and 1-channel, 8 bit masks

    # fast, but can't handle overflows
    if not slow:
        image[:,:,0] = image[:,:,0] + color_delta[0] * (mask[:,:,0] / 255)
        image[:,:,1] = image[:,:,1] + color_delta[1] * (mask[:,:,0] / 255)
        image[:,:,2] = image[:,:,2] + color_delta[2] * (mask[:,:,0] / 255)

    # slower, but no issues with overflows
    else:
        rows, cols = image.shape[:2]
        for row in xrange(rows):
            for col in xrange(cols):
                if mask[row, col, 0] > 0:
                    image[row, col, 0] = min(255, max(0, image[row, col, 0] + color_delta[0]))
                    image[row, col, 1] = min(255, max(0, image[row, col, 1] + color_delta[1]))
                    image[row, col, 2] = min(255, max(0, image[row, col, 2] + color_delta[2]))

    return

有没有一种快速的方法(可能使用一些 numpy 的函数)来获得我的慢速代码当前产生的相同结果？

Answer 1

可能有更好的方法将着色蒙版应用到图像，但如果您想按照您建议的方式进行操作，那么这个简单的剪辑将达到您想要的效果:

import numpy as np

image[:, :, 0] = np.clip(image[:, :, 0] + color_delta[0] * (mask[:, :, 0] / 255), 0, 255)
image[:, :, 1] = np.clip(image[:, :, 1] + color_delta[1] * (mask[:, :, 0] / 255), 0, 255)
image[:, :, 2] = np.clip(image[:, :, 2] + color_delta[2] * (mask[:, :, 0] / 255), 0, 255)

结果是:

如果您的目标是将颜色应用于某个区域，另一种方法是简单地修改色调/饱和度。例如:

mask = np.zeros((image.shape[0], image.shape[1]), dtype=np.bool)
mask[100:200, 100:500] = True

image = cv2.cvtColor(image, cv2.COLOR_BGR2HSV)
image[mask, 0] = 80
image[mask, 1] = 255
image = cv2.cvtColor(image, cv2.COLOR_HSV2BGR)