1. Mouse events

Mouse events are mainly through setMouseCallback Function to bind .

void setMousecallback(const string& winname, MouseCallback onMouse, void* userdata=0)
winname： The name of the window
onMouse： Mouse response function , Callback function . Specifies when each mouse time occurs in the window , Pointer to the called function . The prototype of this function should be void onMouse(int event, int x, int y, int flags, void* param);
userdate： Parameters passed to the callback function

event：
#defineCV_EVENT_MOUSEMOVE 0 Move
#defineCV_EVENT_LBUTTONDOWN 1 Left key press
#defineCV_EVENT_RBUTTONDOWN 2 Right click to press the
#defineCV_EVENT_MBUTTONDOWN 3 Press the key
#defineCV_EVENT_LBUTTONUP 4 Left key up
#defineCV_EVENT_RBUTTONUP 5 Right click to raise
#defineCV_EVENT_MBUTTONUP 6 The middle key rises
#defineCV_EVENT_LBUTTONDBLCLK 7 Next, double-left click on
#defineCV_EVENT_RBUTTONDBLCLK 8 Right click double-click
#defineCV_EVENT_MBUTTONDBLCLK 9 Double-click the key
flag：
#defineCV_EVENT_FLAG_LBUTTON 1 Left drag
#defineCV_EVENT_FLAG_RBUTTON 2 Right click and drag
#defineCV_EVENT_FLAG_MBUTTON 4 Middle drag
#defineCV_EVENT_FLAG_CTRLKEY 8 (8~15) Press Ctrl No release event
#defineCV_EVENT_FLAG_SHIFTKEY 16 (16~31) Press Shift No release event
#defineCV_EVENT_FLAG_ALTKEY 32 (32~39) Press Alt No release event
 

Once the callback function is run, it will listen to the mouse action , It's equivalent to opening a and main Parallel processes , The process will follow main End and end . 

2. normalization

Normalization is to convert the data into an interval of 【0.1】 Data between . Use normalize function .

// Normalization function Original image Output image Maximum minimum value Algorithm
    normalize(image, dst, 1.0, 0, NORM_MINMAX);

Mat dst;
	std::cout << image.type() << std::endl;
//cv_8uc3 turn CV_32F
	image.convertTo(image, CV_32F);
	std::cout << image.type() << std::endl;
	// Normalization function 
	normalize(image, dst, 1.0, 0, NORM_MINMAX);
	std::cout << dst.type() << std::endl;
	imshow(" Image data normalization ", dst);
	// CV_8UC3, CV_32FC3

3. Shrinkage

Zoom function ：resize 

src Input diagram
dst Output chart , The shape is the same as the input diagram , When dsize It's not equal to 0, The size of the output drawing will match dsize identical , When dsize be equal to 0, The output drawing size will be determined by the input drawing size 、fx、fy Calculated
dsize Output size , When the input is 0 when ,fx、fy Nothing can be done 0,dsize =
Size(round(fxsrc.cols),round(fysrc.rows))
fx Horizontal scaling , When the input is 0 when ,fx=(double)dsize.width/src.cols
fy Vertical scaling , When the input is 0 when ,fy=(double)dsize.height/src.rows

interpolation Interpolation Interpolation methods include
CV_INTER_NEAREST Nearest interpolation point method
CV_INTER_LINEAR Bilinear interpolation
CV_INTER_AREA Neighborhood pixel resampling interpolation
CV_INTER_CUBIC Bicube interpolation ,4*4 Complementary points of size
 

4. Image reversal , rotate

function ：flip 

CV_EXPORTS_W void flip(
        InputArray src,  // The input image
        OutputArray dst, // Output graph image
        int flipCode     // <0 Turn left and right upside down ; 0 Upside down ;>0 Turn left and right
        );

Mat dst;
	// flip(image, dst, 0); //  Flip up and down 
	// flip(image, dst, 1); //  Flip left and right 
	flip(image, dst, -1); // 180° rotate 
	imshow(" Image reversal ", dst);