C # Getting started learning ----- simple drawing program

This example shows how to draw various shapes on a form, such as a rectangle, an ellipse, a line, or a text. The running effect is as follows:

 

Implementation process:

(1) create a form application

(2) Add a MenuScrip control and a ToolScrip control.

Change the DisplayStyle attribute to Text for each cell in the ToolScrip control.

 

(3) program code.

1. When creating a menu event, the background of the form is cleared in white to implement the "File Creation" function.

[Csharp]
Private void create ToolStripMenuItem_Click (object sender, EventArgs e)
{
Graphics g = this. CreateGraphics ();
G. Clear (backColor );
ToolStrip1.Enabled = true;
// Create a Bitmap
TheImage = new Bitmap (this. ClientRectangle. Width, this. ClientRectangle. Height );
EditFileName = "new file ";
// Modify the window title
This. Text = "MyDraw \ t" + editFileName;
Ig = Graphics. FromImage (theImage );
Ig. Clear (backColor );
}

 

2. Open the event to open the "open file" dialog box, select the corresponding image, and draw the image to the form.

 

 

[Csharp]
Private void open ToolStripMenuItem_Click (object sender, EventArgs e)
{
OpenFileDialog1.Multiselect = false;
If (openFileDialog1.ShowDialog () = DialogResult. OK)
{
// Modify the window title
This. Text = "MyDraw \ t" + openFileDialog1.FileName;
EditFileName = openFileDialog1.FileName;
TheImage = Image. FromFile (openFileDialog1.FileName );
Graphics g = this. CreateGraphics ();
G. DrawImage (theImage, this. ClientRectangle );
Ig = Graphics. FromImage (theImage );
Ig. DrawImage (theImage, this. ClientRectangle );
// ToolBar can be used
ToolStrip1.Enabled = true;
}
}

(3) Save the Click Event of the menu item to save the image in BMP format as the background of the form.

[Csharp]
Private void save ToolStripMenuItem_Click (object sender, EventArgs e)
{
SaveFileDialog1.Filter = "image (*. bmp) | *. bmp ";
SaveFileDialog1.FileName = editFileName;
If (saveFileDialog1.ShowDialog () = DialogResult. OK)
{
TheImage. Save (saveFileDialog1.FileName, ImageFormat. Bmp );
This. Text = "MyDraw \ t" + saveFileDialog1.FileName;
EditFileName = saveFileDialog1.FileName;
}
}

(4) In the Paint event, draw the Image saved in the Image.

[Csharp]
Private void Form1_Paint (object sender, PaintEventArgs e)
{
// Draw the Image saved in the Image
Graphics g = this. CreateGraphics ();
If (theImage! = Null)
{
G. Clear (Color. White );
G. DrawImage (theImage, this. ClientRectangle );
}
}

(5) Add the Frm_Text.cs text input box.

Add a Window form named Frm_Text and modify the properties of the form:

Change the FormBorderStyle attribute to None;

 

Change the Modifiers attribute to Public.

 

(6) In the form MouseDown event, if the string is currently drawn, the text box is displayed at the current position of the mouse; if the drawing is open, set the starting position of the image.

[Cpp]
Private void Frm_Main_MouseDown (object sender, MouseEventArgs e)
{
If (e. Button = MouseButtons. Left)
{
// If you select text input, the strInput form is opened.
If (drawTool = drawTools. String)
{
Frm_Text inputBox = new Frm_Text ();
InputBox. StartPosition = FormStartPosition. CenterParent;
If (inputBox. ShowDialog () = DialogResult. OK)
{
Graphics g = this. CreateGraphics ();
Font theFont = this. Font;
G. DrawString (inputBox. textBox1.Text, theFont, new SolidBrush (foreColor), e. X, e. Y );
Ig. DrawString (inputBox. textBox1.Text, theFont, new SolidBrush (foreColor), e. X, e. Y );
}
}
// If you start to draw, record the mouse position
Else if (isDrawing =! IsDrawing) = true)
{
StartPoint = new Point (e. X, e. Y );
OldPoint = new Point (e. X, e. Y );
}
}
}
 

(7) In the form MouseMove event, draw the specified image based on the size of the mouse movement.

[Cpp]
Private void form=mousemove (object sender, MouseEventArgs e)
{
Graphics g;
G = this. CreateGraphics ();
 
If (isDrawing)
{
Switch (drawTool)
{
Case drawTools. None:
Break;
Case drawTools. Pen:
// Draw a line segment from the previous point to the current point
G. DrawLine (new Pen (foreColor, 1), oldPoint, new Point (e. X, e. Y ));
Ig. DrawLine (new Pen (foreColor, 1), oldPoint, new Point (e. X, e. Y ));
OldPoint. X = e. X;
OldPoint. Y = e. Y;
Break;
Case drawTools. Line:
// Restore the image before this operation, and then add Line
This. Frm_Main_Paint (this, new PaintEventArgs (this. CreateGraphics (), this. ClientRectangle ));
G. DrawLine (new Pen (foreColor, 1), startPoint, new Point (e. X, e. Y ));
Break;
Case drawTools. Ellipse:
// Restore the image before this operation, and then add Ellipse
This. Frm_Main_Paint (this, new PaintEventArgs (this. CreateGraphics (), this. ClientRectangle ));
G. DrawEllipse (new Pen (foreColor, 1), startPoint. X, startPoint. Y, e. X-startPoint. X, e. Y-startPoint. Y );
Break;
Case drawTools. Rectangle:
// Restore the image before this operation, and then add the Rectangle
This. Frm_Main_Paint (this, new PaintEventArgs (this. CreateGraphics (), this. ClientRectangle ));
G. DrawRectangle (new Pen (foreColor, 1), startPoint. X, startPoint. Y, e. X-startPoint. X, e. Y-startPoint. Y );
Break;
Case drawTools. String:
Break;
Case drawTools. Rubber:
// Draw a wide line segment with the background color
G. DrawLine (new Pen (backColor, 20), oldPoint, new Point (e. X, e. Y ));
Ig. DrawLine (new Pen (backColor, 20), oldPoint, new Point (e. X, e. Y ));
OldPoint. X = e. X;
OldPoint. Y = e. Y;
Break;
}
}
}

(8) In the form MouseUp event, draw a straight line, an ellipse, or a rectangle Based on the selected paint brush.

[Csharp]
Private void form=mouseup (object sender, MouseEventArgs e)
{
IsDrawing = false;
Switch (drawTool)
{
Case drawTools. Line:
Ig. DrawLine (new Pen (foreColor, 1), startPoint, new Point (e. X, e. Y ));
Break;
Case drawTools. Ellipse:
Ig. DrawEllipse (new Pen (foreColor, 1), startPoint. X, startPoint. Y, e. X-startPoint. X, e. Y-startPoint. Y );
Break;
Case drawTools. Rectangle:
Ig. DrawRectangle (new Pen (foreColor, 1), startPoint. X, startPoint. Y, e. X-startPoint. X, e. Y-startPoint. Y );
Break;
}
}

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The following explains why the line moves with the mouse when a straight line is pulled, and when you select a paint brush, move the mouse to draw a line.

There are two Graphics:

(1) Real Scenario graphics. Just the picture above is what I see.

Eg:

Private void Form1_Paint (object sender, PaintEventArgs e)
{
// Draw the Image saved in the Image
Graphics g = this. CreateGraphics ();

(2) Graphic used for temporary storage.

It is created when it is created:

[Csharp]
// Create a Bitmap
TheImage = new Bitmap (this. ClientRectangle. Width, this. ClientRectangle. Height );
EditFileName = "new file ";
// Modify the window title
This. Text = "MyDraw \ t" + editFileName;
Ig = Graphics. FromImage (theImage );
Ig. Clear (backColor );

Display: Display theImage to display the previously saved items in ig.

[Csharp]
Private void Frm_Main_Paint (object sender, PaintEventArgs e)
{
// Draw the Image saved in the Image
Graphics g = this. CreateGraphics ();
If (theImage! = Null)
{
G. Clear (Color. White );
G. DrawImage (theImage, this. ClientRectangle );
}
}

In Form1_MouseMove

If it is a paint brush, save the image to two graphic, so that we can see the moving painting, and finally show all the painting.

If it is a straight line or rectangle, it is first drawn to the first graphics, and only to the second graphic when the mouse is opened.

 

 

From the column chenyujing1234