C # drawing on controls by using GDI,

C # drawing on controls by using GDI,

 

This document uses the chart control and the form to draw a rectangle as an example.

The code is very simple.

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Using System; using System. collections. generic; using System. componentModel; using System. data; using System. drawing; using System. linq; using System. text; using System. windows. forms; using System. IO; using System. configuration; namespace WFApp2 {public partial class data: Form {public data () {InitializeComponent (); // Form g = this. createGraphics (); // chart control g2 = this. chart1.CreateGraphics ();} public Point firstPoint = new Point (0, 0); // the first Point of the mouse is public Point secondPoint = new Point (0, 0 ); // The second point of the mouse is public bool begin = false; // do you want to start drawing a rectangle? // <summary> // draw a rectangle from /// </summary> Graphics g; /// <summary> /// draw a rectangle on the chart1 control /// </summary> Graphics g2; /// <summary> /// press the mouse event on the form /// </summary> /// <param name = "sender"> </param> /// <param name = "e"> </param> private void data_MouseDown (object sender, mouseEventArgs e) {begin = true; firstPoint = new Point (e. x, e. Y );} /// <summary> /// move the mouse over the form to start drawing // </summary> /// <param name = "sender"> </param> // /<param name = "e"> </param> private void data_MouseMove (object sender, mouseEventArgs e) {if (begin) {// clear the form drawing surface, which is equivalent to refreshing the form interface and re-drawing g. clear (this. backColor); // obtain the coordinates secondPoint = new Point (e. x, e. y); // obtain the big or small int minX = Math. min (firstPoint. x, secondPoint. x); int minY = Math. min (firstPoint. y, secondPoint. y); int maxX = Math. max (firstPoint. x, secondPoint. x); int maxY = Math. max (firstPoint. y, secondPoint. y); // frame g. drawRectangle (new Pen (Color. red), minX, minY, maxX-minX, maxY-minY); // ControlPaint. drawReversibleFrame (new Rectangle (minX, minY, maxX-minX, maxY-minY), this. backColor, FrameStyle. dashed );}} /// <summary> /// release the mouse to stop the drawing /// </summary> /// <param name = "sender"> </param> // <param name = "e"> </param> private void data_MouseUp (object sender, mouseEventArgs e) {begin = false ;} /// <summary> /// move the mouse over the chart control /// </summary> /// <param name = "sender"> </param> // /<param name = "e"> </param> private void chart1_MouseMove (object sender, mouseEventArgs e) {if (begin) {// drawing on the chart again. The clear method cannot be used here. clear clears the chart control of the entire drawing interface and clears this. refresh (); // obtain the coordinates secondPoint = new Point (e. x, e. y); int minX = Math. min (firstPoint. x, secondPoint. x); int minY = Math. min (firstPoint. y, secondPoint. y); int maxX = Math. max (firstPoint. x, secondPoint. x); int maxY = Math. max (firstPoint. y, secondPoint. y); // draw a rectangle g2.DrawRectangle (new Pen (Color. red), minX, minY, maxX-minX, maxY-minY );}} /// <summary> /// release the mouse to stop the drawing /// </summary> /// <param name = "sender"> </param> // <param name = "e"> </param> private void chart1_MouseUp (object sender, mouseEventArgs e) {begin = false ;} /// <summary> /// press the mouse on the chart control /// </summary> /// <param name = "sender"> </param> /// <param name = "e"> </param> private void chart1_MouseDown (object sender, mouseEventArgs e) {begin = true; firstPoint = new Point (e. x, e. Y );}}}

C Language & |! What are

& Is the address fetch operator used to extract the address of a variable.
For example, if you define a variable, the system will allocate a space in the memory during compilation.
The location of the space in the memory is its address. & Extract its address.
E. g int a; assign an address to it during compilation, for example, 2000; & a is 2000.
If an integer pointer Variable p, p = & a; is defined, the address 2000 of a is assigned to p. P = 2000 after running.
Another example is scanf ("% d", & a). When you enter 3, it first knows the address of a according to & a, and finds the space of a in the memory by the address, write 3 to this space.
* Is a pointer operator, which is opposite to &. It extracts the value of a Variable Based on the address of the variable.
For example, * the value of a is 3 of variable.
The following is a summary of the pointer used in the definition and description.
Int * p; defines a pointer to integer data.
Int * p [n]; defines the pointer array p, which consists of n pointer elements pointing to integer data.
Int (* p) [n]; p is the pointer variable pointing to a one-dimensional array containing n elements.
Int * p (); p is the function that returns a pointer pointing to integer data.
Int (* p) (); p is the pointer to the function. This function returns an integer value.
Int ** p; p is a pointer variable that points to an integer Data Pointer variable.
If you want to learn more about the system, you can refer to tan haoqiang's c Programming (the third edition), which is easy to understand. Is a good C language learning material.

C Language & |! What are

& Is the address fetch operator used to extract the address of a variable.
For example, if you define a variable, the system will allocate a space in the memory during compilation.
The location of the space in the memory is its address. & Extract its address.
E. g int a; assign an address to it during compilation, for example, 2000; & a is 2000.
If an integer pointer Variable p, p = & a; is defined, the address 2000 of a is assigned to p. P = 2000 after running.
Another example is scanf ("% d", & a). When you enter 3, it first knows the address of a according to & a, and finds the space of a in the memory by the address, write 3 to this space.
* Is a pointer operator, which is opposite to &. It extracts the value of a Variable Based on the address of the variable.
For example, * the value of a is 3 of variable.
The following is a summary of the pointer used in the definition and description.
Int * p; defines a pointer to integer data.
Int * p [n]; defines the pointer array p, which consists of n pointer elements pointing to integer data.
Int (* p) [n]; p is the pointer variable pointing to a one-dimensional array containing n elements.
Int * p (); p is the function that returns a pointer pointing to integer data.
Int (* p) (); p is the pointer to the function. This function returns an integer value.
Int ** p; p is a pointer variable that points to an integer Data Pointer variable.
If you want to learn more about the system, you can refer to tan haoqiang's c Programming (the third edition), which is easy to understand. Is a good C language learning material.