详解cv2.addWeighted函数【使用 OpenCV 添加（混合）两个图像-Python版本】

简介

有的时候我们需要将两张图片在alpha通道进行混合，比如深度学习数据集增强方式MixUp。OpenCV的addWeighted提供了相关操作，此篇博客将详细介绍这个函数，并给出代码示例。🚀🚀

函数原型

$$\mathrm{outputImg}=\mathrm{saturate}(\alpha \ast inputImg1+\beta \ast inputImg2+\gamma )$$

cv.addWeighted(	src1, alpha, src2, beta, gamma[, dst[, dtype]]	) -> dst
1

代码示例

import cv2
import matplotlib.pyplot as plt

# 加载两张图片
img1 = cv2.imread(filename="Lenna.png")
img2 = cv2.imread(filename="horses.jpg")

# 将两张图片都调整到640*640
shape1 = img1.shape  # HWC
shape2 = img2.shape  # HWC
max1 = max(shape1[0], shape1[1])
max2 = max(shape2[0], shape2[1])
img1 = cv2.copyMakeBorder(
    src=img1,
    top=int((max1 - shape1[0])/2),
    bottom=int((max1 - shape1[0])/2),
    left=int((max1 - shape1[1])/2),
    right=int((max1 - shape1[1])/2),
    borderType=cv2.BORDER_REFLECT101,
)
img1 = cv2.resize(src=img1, dsize=(640, 640), interpolation=cv2.INTER_LINEAR)
img2 = cv2.copyMakeBorder(
    src=img2,
    top=int((max2 - shape2[0])/2),
    bottom=int((max2 - shape2[0])/2),
    left=int((max2 - shape2[1])/2),
    right=int((max2 - shape2[1])/2),
    borderType=cv2.BORDER_REFLECT101,
)
img2 = cv2.resize(src=img2, dsize=(640, 640), interpolation=cv2.INTER_LINEAR)

# 按照比例将两张图片进行混合
alpha = 0.5
beta = 1.0 - alpha
img_blending = cv2.addWeighted(src1=img1, alpha=alpha, src2=img2, beta=beta, gamma=.0)

# 绘制图片
fig = plt.figure(figsize=(9, 3))
fig.suptitle(t="Blend two images")

ax1 = fig.add_subplot(1, 3, 1)
ax2 = fig.add_subplot(1, 3, 2)
ax3 = fig.add_subplot(1, 3, 3)

ax1.set_title(label="image1")
ax1.spines["top"].set_visible(b=False)
ax1.spines["bottom"].set_visible(b=False)
ax1.spines["left"].set_visible(b=False)
ax1.spines["right"].set_visible(b=False)
ax1.axes.xaxis.set_visible(b=False)
ax1.axes.yaxis.set_visible(b=False)
ax1.imshow(X=cv2.cvtColor(src=img1, code=cv2.COLOR_BGR2RGB))

ax2.set_title(label="image2")
ax2.spines["top"].set_visible(b=False)
ax2.spines["bottom"].set_visible(b=False)
ax2.spines["left"].set_visible(b=False)
ax2.spines["right"].set_visible(b=False)
ax2.axes.xaxis.set_visible(b=False)
ax2.axes.yaxis.set_visible(b=False)
ax2.imshow(X=cv2.cvtColor(src=img2, code=cv2.COLOR_BGR2RGB))

ax3.set_title(label="blending image")
ax3.spines["top"].set_visible(b=False)
ax3.spines["bottom"].set_visible(b=False)
ax3.spines["left"].set_visible(b=False)
ax3.spines["right"].set_visible(b=False)
ax3.axes.xaxis.set_visible(b=False)
ax3.axes.yaxis.set_visible(b=False)
ax3.imshow(X=cv2.cvtColor(src=img_blending, code=cv2.COLOR_BGR2RGB))

plt.show()



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参考资料

1. Computer Vision: Algorithms and Applications
2. OpenCV文档：Adding (blending) two images using OpenCV👍
3. OpenCV文档：addWeighted() 🚀

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