Getting started with data visualization

This is a Earth salt   Of the 174 Original articles

1

Hello everyone , I am earth salt .

In today's qml The function of displaying and hiding historical curves and only adding data is realized in the .

And the examples of multiple axes and crosshairs are run through .

Further understanding of data visualization .

2

Today, I have a new understanding of macro definitions .

（‘a’ <= s[++i] && s[++i] <= 'z' ? (c) - 'a' + 'A' : s[++i]）

You can see , The macro runs two ++i, In addition, when there is no macro, there is a ++i.

therefore , The result is D, instead of B.

Allied ：

such as #define MAX(a,b) ((a)>(b)?(a):(b))

Then MAX(1+2,value) It will be replaced by ：

((1+2)>(value)?(1+2):(value))

3

Mr. Liu led the students in their study OpenCV.

Once across the wilderness , Fly over the mountains at once , Traverse the Westward Journey , Ride the wind and waves , Wonderful .

Come and experience ：

Isn't it ？ Still traversing OpenCV Images , Try to accelerate with the pointer ！

https://mp.weixin.qq.com/s/-4u02x9S7yI3xKm0FBs_dA

Click on the original link , You can see .

Since this formula is to calculate the data address , We know that the pointer points to the data address , As it should be, we can pass data Pointer to access elements .

for (int row = 0; row < h; row++) {
        uchar* uc_pixel = src.data + row*src.step;
        for (int col = 0; col < w; col++) {
            uc_pixel[0] = 255 - uc_pixel[0];
            uc_pixel[1] = 255 - uc_pixel[1];
            uc_pixel[2] = 255 - uc_pixel[2];
            uc_pixel += 3;
        }
    }

4

After work , evening 7 spot , Experienced the new taikoori square with male compatriots , It's delicious .

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