大约有 47,000 项符合查询结果（耗时：0.0306秒） [XML]
How to check if hex color is “too black”?
...rceived brightness.
Assuming a six character colour:
var c = c.substring(1); // strip #
var rgb = parseInt(c, 16); // convert rrggbb to decimal
var r = (rgb >> 16) & 0xff; // extract red
var g = (rgb >> 8) & 0xff; // extract green
var b = (rgb >> 0) & 0xff;...
How do I efficiently iterate over each entry in a Java Map?
...
1
2
Next
5153
...
Position of least significant bit that is set
...
170
Bit Twiddling Hacks offers an excellent collection of, er, bit twiddling hacks, with performan...
Fast way to get image dimensions (not filesize)
...
195
The file command prints the dimensions for several image formats (e.g. PNG, GIF, JPEG; recent...
Java - get pixel array from image
...
182
I was just playing around with this same subject, which is the fastest way to access the pixel...
How do I get indices of N maximum values in a NumPy array?
...
16 Answers
16
Active
...
How many double numbers are there between 0.0 and 1.0?
...or example, that's the number of distinct doubles between 0.5 included and 1.0 excluded, and exactly that many also lie between 1.0 included and 2.0 excluded, and so forth.
Counting the doubles between 0.0 and 1.0 is harder than doing so between powers of two, because there are many powers of two i...
How do I cast a string to integer and have 0 in case of error in the cast with PostgreSQL?
...
13 Answers
13
Active
...
pyplot scatter plot marker size
...d the output they produce.
# doubling the width of markers
x = [0,2,4,6,8,10]
y = [0]*len(x)
s = [20*4**n for n in range(len(x))]
plt.scatter(x,y,s=s)
plt.show()
gives
Notice how the size increases very quickly. If instead we have
# doubling the area of markers
x = [0,2,4,6,8,10]
y = [0]*len(...
From ND to 1D arrays
...
Use np.ravel (for a 1D view) or np.ndarray.flatten (for a 1D copy) or np.ndarray.flat (for an 1D iterator):
In [12]: a = np.array([[1,2,3], [4,5,6]])
In [13]: b = a.ravel()
In [14]: b
Out[14]: array([1, 2, 3, 4, 5, 6])
Note that ravel() ret...