我有一個2D numpy 陣列，我想找到水平線和垂直線的邊界點。
gray_img = np.array([[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 255, 255, 255, 255, 255, 0],
[0, 255, 255, 255, 255, 255, 255, 255, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 255, 255, 255, 255],
[0, 255, 255, 0, 0, 255, 255, 255, 255],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0]])
desired_outcome = [ [[1,1],[10,1]],
[[1,2],[10,2]],
[[1,3],[2,3]], ...]
這是我要查找的行：
稍后，我想洗掉較小的線以僅保留那些距離超過 2 點的線。
uj5u.com熱心網友回復：
垂直線：
m = np.diff(gray_img, 1, 0) # get discrete difference along the 0-axis
m = np.argwhere(m != 0) # get indices where value is not zero
m = m[np.lexsort(m.T)] # sort indices first 1-column then 0-column
m[::2,0] = 1 #
輸出：
[[ 1 1]
[10 1]
[ 1 2]
[10 2]
[ 1 3]
[ 2 3]
[ 1 4]
[ 2 4]
[ 1 5]
[ 2 5]
[ 6 5]
[ 7 5]
[ 1 6]
[ 2 6]
[ 6 6]
[ 7 6]
[ 1 7]
[ 2 7]
[ 6 7]
[ 7 7]
[ 6 8]
[ 7 8]]
水平線：
m = np.diff(gray_img, 1, 1, append=np.zeros((gray_img.shape[0], 1)))
m = np.argwhere(m != 0)
m[::2,1] = 1
輸出：
[[ 1 1]
[ 1 7]
[ 2 1]
[ 2 7]
[ 3 1]
[ 3 2]
[ 4 1]
[ 4 2]
[ 5 1]
[ 5 2]
[ 6 1]
[ 6 2]
[ 6 5]
[ 6 8]
[ 7 1]
[ 7 2]
[ 7 5]
[ 7 8]
[ 8 1]
[ 8 2]
[ 9 1]
[ 9 2]
[10 1]
[10 2]]
uj5u.com熱心網友回復：
這是基于前綴和的水平線演算法：
# Do a prefix sum to get the lengths of each line.
gray_cumsum = np.cumsum(gray_img / 255, axis=1)
gray_cumsum[:, 1:] = gray_cumsum[:, 1:] * (gray_cumsum[:, 1:] != gray_cumsum[:, :-1])
# Reindex all the points so each line starts at 1.
start_num = gray_cumsum.copy()
a = start_num[:,1:-1] != 0
b = start_num[:,:-2] == 0
c = start_num[:,2:] != 0
start_num[:,1:-1] = start_num[:,1:-1] * np.logical_and(np.logical_and(a, b), c)
start_num[:, -1] = 0
start_num = np.maximum.accumulate(start_num, axis=1)
gray_cumsum = np.maximum(gray_cumsum - start_num, 0)
# Detect only the ends of each line.
gray_cumsum[:,:-1] = gray_cumsum[:,:-1] * (gray_cumsum[:,1:] == 0)
# Get the starting and endings points of each line.
end_points = np.stack(gray_cumsum.nonzero(), axis=-1)
lengths = gray_cumsum[gray_cumsum.nonzero()]
start_points = end_points.copy()
start_points[:, 1] = start_points[:, 1] - lengths
print(start_points)
print(end_points)
只需更改索引即可獲得垂直線。您可以使用長度陣列來過濾掉您想要的行。
uj5u.com熱心網友回復：
編輯：收集水平線和垂直線，我還減少了我在初稿中使用的一些多余的比較：掃描時有一個方向，因此只需要更新右/下端坐標，而左/上是??恒定的，等于開始掃描當前線段。還有一些多余的代碼可以壓縮。
EDIT2：添加了問題中串列的最終格式。
它首先查找并列出水平線，如果在您的示例輸出中必須首先出現垂直線，那么只需將第二個遍歷放在頂部。
import numpy as np
gray_img = np.array([[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 255, 255, 255, 255, 255, 0],
[0, 255, 255, 255, 255, 255, 255, 255, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 255, 255, 255, 255],
[0, 255, 255, 0, 0, 255, 255, 255, 255],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0]])
bounds = []
a = gray_img
#SCANNING HORIZONTAL LINES
for y in range(0,a.shape[0]):
print("\nY=",y)
found = False #set to True when scanning a line
left_x, right_x = 0,0
top_y = y; bottom_y = y
if a[y,0]==255:
top_y = min(top_y, y)
bottom_y = max(bottom_y,y)
found = True
for x in range(0,a.shape[1]): #
#while x < len(a[1]) or x!==0 #...
if a[y,x]==255 and not found: #first item
found = True
right_x = x
left_x = x
#right_x = max(right_x, x)
#left_x = x # min(left_x, x)
print("START",top_y, bottom_y, left_x, right_x)
else:
if a[y,x]==255 and found: #running line
right_x = max(right_x, x)
#left_x = min(left_x, x)
#print(top_y, bottom_y, left_x, right_x)
if a[y,x]==0 and found: #end of a running line
bounds.append([top_y, left_x, bottom_y, right_x])
print(a[y,x],end=",")
found = False
if found: #end of a running line matches the end of the dimension/line
bounds.append([top_y, left_x, bottom_y, right_x])
print(a[y,x],end=",")
found = False
print("\n")
print(bounds)
print(a.shape)
#print(f"LEN= {a.shape[0])}, {a.shape[1])}")
#SCANNING VERTICAL LINES
for x in range(0,a.shape[1]):
print("\nY=",y)
found = False #set to True when scanning a line
left_x, right_x = x,x
top_y = 0; bottom_y = 0
if a[0,x]==255:
top_y = min(top_y, y)
bottom_y = max(bottom_y,y)
found = True
for y in range(0,a.shape[0]): #
#while x < len(a[1]) or x!==0 #...
if a[y,x]==255 and not found: #first item
found = True
#right_x = max(right_x, x)
bottom_y = y
top_y = y
left_x = x # min(left_x, x)
print("START",top_y, bottom_y, left_x, right_x)
else:
if a[y,x]==255 and found: #running line
bottom_y = y #max(right_x, x)
#top_y = min(left_x, x)
#print(top_y, bottom_y, left_x, right_x)
if a[y,x]==0 and found: #end of a running line
bounds.append([top_y, left_x, bottom_y, right_x])
print(a[y,x],end=",")
found = False
if found: #end of a running line matches the end of the dimension/line
bounds.append([top_y, left_x, bottom_y, right_x])
print(a[y,x],end=",")
found = False
print("\n")
print(bounds)
print(a.shape)
# [[1, 1, 1, 7], [2, 1, 2, 7], [3, 1, 3, 2], [4, 1, 4, 2], [5, 1, 5, 2], [6, 1, 6, 2], [6, 5, 6, 8], [7, 1, 7, 2], [7, 5, 7, 8], [8, 1, 8, 2], [9, 1, 9, 2], [10, 1, 10, 2], [1, 1, 10, 1], [1, 2, 10, 2], [1, 3, 2, 3], [1, 4, 2, 4], [1, 5, 2, 5], [6, 5, 7, 5], [1, 6, 2, 6], [6, 6, 7, 6], [1, 7, 2, 7], [6, 7, 7, 7], [6, 8, 7, 8]]
#(15, 9)
#This list has to be additionally traversed in order to form [ [[1,1][1,7]], [...]] e.g.:
fm = []
for i in bounds:
#i=[1,1,1,7] etc.
f = [[i[0],i[1]],[i[2],i[3]]]
fm.append(f)
print(fm)
[[[1, 1], [1, 7]], [[2, 1], [2, 7]], [[3, 1], [3, 2]], [[4, 1], [4, 2]], [[5, 1], [5, 2]], [[6, 1], [6, 2]], [[6, 5], [6, 8]], [[7, 1], [7, 2]], [[7, 5], [7, 8]], [[8, 1], [8, 2]], [[9, 1], [9, 2]], [[10, 1], [10, 2]], [[1, 1], [10, 1]], [[1, 2], [10, 2]], [[1, 3], [2, 3]], [[1, 4], [2, 4]], [[1, 5], [2, 5]], [[6, 5], [7, 5]], [[1, 6], [2, 6]], [[6, 6], [7, 6]], [[1, 7], [2, 7]], [[6, 7], [7, 7]], [[6, 8], [7, 8]]]
然后您可以遍歷結果串列并計算該距離（或者您的意思是線的長度）并僅將較長的線傳輸到另一個串列。
uj5u.com熱心網友回復：
這是你想要的嗎？
import pandas as pd
import numpy as np
a = np.array([[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 255, 255, 255, 255, 255, 0],
[0, 255, 255, 255, 255, 255, 255, 255, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 255, 255, 255, 255],
[0, 255, 255, 0, 0, 255, 255, 255, 255],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 255, 255, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0]])
a = a[a != 0]
list = a.tolist()
print(list)
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