我們經常會有對圖像邊緣做擴展的需求.比如
- 希望卷積后得到的矩陣大小不變
- 希望改變圖像大小,但是不改變寬高比
opencv實現
opencv中使用copyMakeBorder()來完成這一功能
api
- src是原圖像矩陣
- dst是新圖像矩陣
- top/bottom/left/right是邊界擴展的大小(比如5就代表5個像素)
- borderType
- value是擴充的像素填什么值
borderType分兩種:
- BORDER_CONSTANT
邊緣填充用固定像素值,比如填充黑邊,就用0,白邊255 - BORDER_REPLICATE
用原始圖像相應的邊緣的像素去做填充,看起來有一種把圖像邊緣"拉糊了"的效果
opencv示例
import sys
import cv2 as cv
def test():
src = cv.imread("/home/sc/disk/keepgoing/opencv_test/lights.jpeg")
top = int(0.05 * src.shape[0]) # shape[0] = rows
bottom = top
left = int(0.04 * src.shape[1]) # shape[1] = cols
right = left
value = [0,0,0]
borderType = cv.BORDER_CONSTANT
dst1 = cv.copyMakeBorder(src, top, bottom, left, right, borderType, None, value)
borderType = cv.BORDER_REPLICATE
dst2 = cv.copyMakeBorder(src, top, bottom, left, right, borderType, None, value)
cv.imshow("blackborder",dst1)
cv.imshow("BORDER_REPLICATE",dst2)
if 27 == cv.waitKey():
cv.destroyAllWindows()
test()
效果如下:
