OpenCV Python 图像相加与透明色转换

将两幅图添加起来,构成一幅新的图像,并尝试将一个PNG的透明背景转换为特定的颜色。

生成纯背景

以下代码生成一个纯色背景JPG,颜色为照片底板的蓝(R:60 G:140 B:220)。在用OpenCV创建图像时,颜色按BGR

import cv2
import numpy as np

def create_blank(width, height, rgb_color=(60, 140, 220)):
    """Create new image(numpy array) filled with certain color in RGB"""
    # Create black blank image
    image = np.zeros((height, width, 3), np.uint8)

    # Since OpenCV uses BGR, convert the color first
    color = tuple(reversed(rgb_color))
    # Fill image with color
    image[:] = color

    return image

img = cv2.imread('dog.png')
(rows, cols) = img.shape[:2]
blank = create_blank(cols, rows)
cv2.imwrite('blue.jpg', blank)

蓝色背景

两个图像相加

两个图像大小相同的情况下,可以通过矩阵叠加方法——OpenCV Python中,为cv2.add,合并在一起,代码如下:

import cv2

img1 = cv2.imread('dog.png')
img2 = cv2.imread('blue.jpg')

# Add 2 images
img_dst = cv2.add(img1, img2)

# Display the processed images 
cv2.imshow('img', img_dst )
cv2.imwrite('add.jpg', img_dst)

# Wait for a key press and then close the windows
cv2.waitKey(0)
cv2.destroyAllWindows()

加法狗

显然,这是矩阵个元素数值的相加,那么,假如要把透明背景用别的颜色替换,而不是这样相加,又该“如何应对”?

透明色转换

读入一个有透明背景的png图片,然后我们会发现,它的α通道是0。

import cv2

# Read a png with alpha channel
img = cv2.imread('dog.png', cv2.IMREAD_UNCHANGED)
cv2.imshow('img', img)
cv2.imwrite('dog.png', img)
# Wait for a key press and then close the windows
cv2.waitKey(0)
cv2.destroyAllWindows()

对于图像的透明部分,其值为[0,0,0,0],那么我们可以将该透明部分修改成对应的颜色,具体见函数transparent2bgra_color

import cv2
import numpy as np

def transparent2bgra_color(img, bgra_color=(255, 255, 255, 255)):
    # Avoid the side-effect
    res = img.copy()
    res[img[:, :, 3] == 0] = bgra_color
    return res

# Read the png image with alpha channel
origin_img = cv2.imread('dog.png', cv2.IMREAD_UNCHANGED)
dst_img = transparent2bgra_color(origin_img, bgra_color=(220, 140, 60, 255))
black_dog = transparent2bgra_color(origin_img, bgra_color=(0, 0, 0, 255))

cv2.imshow('Origin', origin_img)
cv2.imshow('Converted', dst_img)
cv2.imshow('Black', black_dog)
cv2.imwrite('new_dog.png', dst_img)
cv2.imwrite('black_dog.png', black_dog)
# Wait for a key press and then close the windows
cv2.waitKey(0)
cv2.destroyAllWindows()

Origin:
原始图像
Converted:
转换后图像
Black:
黑色背景的狗狗

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转载自blog.csdn.net/Humbunklung/article/details/140909131