mirror of
https://github.com/opencv/opencv.git
synced 2025-06-07 09:25:45 +08:00
Merge pull request #13103 from alalek:fix_doc_links_3.4
This commit is contained in:
commit
142a07cbbf
@ -69,7 +69,7 @@ to an integer format. Then we use a simple look and the upper formula to calcula
|
||||
No OpenCV specific stuff here.
|
||||
|
||||
Another issue is how do we measure time? Well OpenCV offers two simple functions to achieve this
|
||||
@ref cv::getTickCount() and @ref cv::getTickFrequency() . The first returns the number of ticks of
|
||||
cv::getTickCount() and cv::getTickFrequency() . The first returns the number of ticks of
|
||||
your systems CPU from a certain event (like since you booted your system). The second returns how
|
||||
many times your CPU emits a tick during a second. So to measure in seconds the number of time
|
||||
elapsed between two operations is easy as:
|
||||
@ -98,7 +98,7 @@ example in case of an BGR color system:
|
||||
Note that the order of the channels is inverse: BGR instead of RGB. Because in many cases the memory
|
||||
is large enough to store the rows in a successive fashion the rows may follow one after another,
|
||||
creating a single long row. Because everything is in a single place following one after another this
|
||||
may help to speed up the scanning process. We can use the @ref cv::Mat::isContinuous() function to *ask*
|
||||
may help to speed up the scanning process. We can use the cv::Mat::isContinuous() function to *ask*
|
||||
the matrix if this is the case. Continue on to the next section to find an example.
|
||||
|
||||
The efficient way
|
||||
@ -155,7 +155,7 @@ elements in the image. Its basic usage is to specify the row and column number o
|
||||
to access. During our earlier scanning methods you could already observe that is important through
|
||||
what type we are looking at the image. It's no different here as you need to manually specify what
|
||||
type to use at the automatic lookup. You can observe this in case of the gray scale images for the
|
||||
following source code (the usage of the + @ref cv::at() function):
|
||||
following source code (the usage of the + cv::Mat::at() function):
|
||||
|
||||
@snippet how_to_scan_images.cpp scan-random
|
||||
|
||||
@ -169,12 +169,12 @@ new row pointer for what we use the C operator[] to acquire the column element.
|
||||
|
||||
If you need to do multiple lookups using this method for an image it may be troublesome and time
|
||||
consuming to enter the type and the at keyword for each of the accesses. To solve this problem
|
||||
OpenCV has a @ref cv::Mat_ data type. It's the same as Mat with the extra need that at definition
|
||||
OpenCV has a cv::Mat_ data type. It's the same as Mat with the extra need that at definition
|
||||
you need to specify the data type through what to look at the data matrix, however in return you can
|
||||
use the operator() for fast access of items. To make things even better this is easily convertible
|
||||
from and to the usual @ref cv::Mat data type. A sample usage of this you can see in case of the
|
||||
from and to the usual cv::Mat data type. A sample usage of this you can see in case of the
|
||||
color images of the upper function. Nevertheless, it's important to note that the same operation
|
||||
(with the same runtime speed) could have been done with the @ref cv::at() function. It's just a less
|
||||
(with the same runtime speed) could have been done with the cv::Mat::at function. It's just a less
|
||||
to write for the lazy programmer trick.
|
||||
|
||||
The Core Function
|
||||
@ -183,7 +183,7 @@ The Core Function
|
||||
This is a bonus method of achieving lookup table modification in an image. In image
|
||||
processing it's quite common that you want to modify all of a given image values to some other value.
|
||||
OpenCV provides a function for modifying image values, without the need to write the scanning logic
|
||||
of the image. We use the @ref cv::LUT() function of the core module. First we build a Mat type of the
|
||||
of the image. We use the cv::LUT() function of the core module. First we build a Mat type of the
|
||||
lookup table:
|
||||
|
||||
@snippet how_to_scan_images.cpp table-init
|
||||
|
Loading…
Reference in New Issue
Block a user