C # GDI + programming 10 basic tricks two

5. Gradient Fill

You need to use two brushes:

Linear gradient Brush (LinearGradientBrush)

Path gradient Brush (Pathguadientbrush)

private void Button4_Click (Object Sender,system.eventargs e)

{

Drawing surface

Graphics g =this.pictureboxii1.creategraphics ();

G.fillrectangle (Brushes.white,this.pictureboxii1.clientrectangle);

Define a linear gradient brush

LinearGradientBrush Lgbrush =

New LinearGradientBrush (

New Point (0, 10),

New Point (150, 10),

Color.FromArgb (255, 0, 0),

Color.FromArgb (0, 255, 0));

Pen pen = new Pen (lgbrush);

Draw a straight line segment with a linear brush gradient effect pen and fill a rectangle

G.drawline (pen, 10, 130, 500, 130);

G.fillrectangle (Lgbrush, 10, 150, 370, 30);

Define a path and add an ellipse

GraphicsPath GP = new GraphicsPath ();

Gp. AddEllipse (10, 10, 200, 100);

Use this path to define the path gradient brush

PathGradientBrush brush =

New PathGradientBrush (GP);

Color array

color[] Colors = {

Color.FromArgb (255, 0, 0),

Color.FromArgb (100, 100, 100),

Color.FromArgb (0, 255, 0),

Color.FromArgb (0, 0, 255)};

Define color gradient ratios

Float[] r = {0.0f, 0.3f, 0.6f, 1.0f};

ColorBlend blend = new ColorBlend ();

Blend. Colors = Colors;

Blend. positions = R;

Brush. Interpolationcolors = blend;

Fills a rectangle outside the ellipse

G.fillrectangle (brush, 0, 0, 210, 110);

Define a second path gradient brush with a path with an ellipse added

GraphicsPath GP2 = new GraphicsPath ();

GP2. AddEllipse (300, 0, 200, 100);

PathGradientBrush brush2 = new PathGradientBrush (GP2);

Set center point position and color

Brush2. CenterPoint = new PointF (450, 50);

Brush2. Centercolor = Color.FromArgb (0, 255, 0);

Set Border color

Color[] Color2 = {Color.FromArgb (255, 0, 0)};

Brush2. Surroundcolors = Color2;

Fills the ellipse with a second gradient brush

G.fillellipse (BRUSH2, 300, 0, 200, 100);

}

6. GDI + coordinate system

Universal coordinate system-user-defined coordinate system.

Page coordinate system--virtual coordinate system.
Device coordinate system--screen coordinate system.

When the units of the page coordinate system and the device coordinate system are pixels, they are the same.

private void Button10_click (object sender, System.eventargse)

{

Graphics g = this.pictureBoxII1.CreateGraphics ();

G.clear (Color.White);

This. Draw (g);

}

private void Draw (Graphics g)

{

G.drawline (Pens.black, 10, 10, 100, 100);

G.drawellipse (Pens.black, 50, 50, 200, 100);

G.drawarc (Pens.black, 100, 10, 100, 100, 20, 160);

G.drawrectangle (Pens.green, 50, 200, 150, 100);

}

private void Button5_click (object sender, System.EventArgs e)

{

Move left

Graphics g = this.pictureBoxII1.CreateGraphics ();

G.clear (Color.White);

G.translatetransform (-50, 0);

This. Draw (g);

}

private void Button6_click (object sender, System.EventArgs e)

{

Move right

Graphics g = this.pictureBoxII1.CreateGraphics ();

G.clear (Color.White);

G.translatetransform (50, 0);

This. Draw (g);

}

private void Button7_click (object sender, System.EventArgs e)

{

Rotating

Graphics g = this.pictureBoxII1.CreateGraphics ();

G.clear (Color.White);

G.rotatetransform (-30);

This. Draw (g);

}

private void Button8_click (object sender, System.EventArgs e)

{

Amplification

Graphics g = this.pictureBoxII1.CreateGraphics ();

G.clear (Color.White);

G.scaletransform (1.2f, 1.2f);

This. Draw (g);

}

private void Button9_click (object sender, System.EventArgs e)

{

Narrow

Graphics g = this.pictureBoxII1.CreateGraphics ();

G.clear (Color.White);

G.scaletransform (0.8f, 0.8f);

This. Draw (g);

}

7. Global coordinates-transformations can have an impact on each element on the drawing surface. Typically used to set a universal coordinate system.

The next program moves the original point to the center of the control, and the y-axis is facing upward.

Draw a circle first

Graphics g = e.graphics;

G.fillrectangle (Brushes.white, this. ClientRectangle);

G.drawellipse (Pens.black,-100,-100, 200, 200);

To make the y-axis forward upward, it must be mirrored relative to the x-axis

The transformation matrix is [1,0,0,-1,0,0]

Matrix mat = new Matrix (1, 0, 0,-1, 0, 0);

G.transform = Mat;

Rectangle rect = this. ClientRectangle;

int w = rect. Width;

int h = rect. Height;

G.translatetransform (W/2,-H/2);

Make a circle with a radius of 100, centered on the origin.

G.drawellipse (pens.red,-100,-100, 200, 200);
G.translatetransform (100, 100);

G.drawellipse (Pens.green,-100,-100, 200, 200);

G.scaletransform (2, 2);

G.drawellipse (Pens.blue,-100,-100, 200, 200);

8, local coordinate system--only some graphics are transformed, while other graphic elements are unchanged.

protected override void OnPaint (PaintEventArgs e)

{

Graphics g = e.graphics;

Customer area set to White

G.fillrectangle (Brushes.white, this. ClientRectangle);

Y-axis facing up

Matrix mat = new Matrix (1, 0, 0,-1, 0, 0);

G.transform = Mat;

Move coordinate origin to form center

Rectangle rect = this. ClientRectangle;

int w = rect. Width;

int h = rect. Height;

G.translatetransform (W/2,-H/2);

Draw an ellipse under global coordinates

G.drawellipse (pens.red,-100,-100, 200, 200);

G.fillrectangle (Brushes.black,-108, 0, 8, 8);

G.fillrectangle (brushes.black, 100, 0, 8, 8);

G.fillrectangle (brushes.black, 0, 100, 8, 8);

G.fillrectangle (brushes.black, 0,-108, 8, 8);

Create an ellipse and transform it in a local coordinate system

GraphicsPath GP = new GraphicsPath ();

Gp. AddEllipse (-100,-100, 200, 200);

Matrix MAT2 = new Matrix ();

Translation

Mat2. Translate (150, 150);

Rotating

Mat2. Rotate (30);

Gp. Transform (MAT2);

G.drawpath (Pens.blue, GP);

Pointf[] p = GP. pathpoints;

G.fillrectangle (Brushes.black, p[0]. X-2, P[0]. Y+2, 4, 4);

G.fillrectangle (Brushes.black, p[3]. X-2, P[3]. Y+2, 4, 4);

G.fillrectangle (Brushes.black, p[6]. X-4, P[6]. Y-4, 4, 4);

G.fillrectangle (Brushes.black, p[9]. X-4, P[9]. Y-4, 4, 4);
Gp. Dispose ();
Base. OnPaint (e);

}

9. Alpha Blending

A of Color.FromArgb () is Alpha. The alpha value ranges from 0 to 255. 0 means full transparency and 255 is completely opaque.

Current color = foreground color xalpha/255+ background x (255-alpha)/255

protected override void OnPaint (PaintEventArgs e)

{

Graphics g = e.graphics;

Create a fill Rectangle

SolidBrush brush = new SolidBrush (color.blueviolet);

G.fillrectangle (Brush, 180, 70, 200, 150);

Creates a bitmap with a transparency effect between two bitmaps

Bitmap bm1 = new Bitmap (200, 100);

Graphics bg1 = Graphics.fromimage (BM1);

SolidBrush Redbrush =

New SolidBrush (Color.FromArgb (210, 255, 0, 0));

SolidBrush Greenbrush =

New SolidBrush (Color.FromArgb (210, 0, 255, 0));

Bg1. FillRectangle (redbrush, 0, 0, 150, 70);

Bg1. FillRectangle (Greenbrush, 30, 30, 150, 70);

G.drawimage (BM1, 100, 100);

Creates a bitmap where there are no transparency effects between two bitmaps

Bitmap bm2 = new Bitmap (200, 100);

Graphics Bg2 = Graphics.fromimage (BM2);

Bg2.compositingmode = compositingmode.sourcecopy;

Bg2. FillRectangle (redbrush, 0, 0, 150, 170);

Bg2. FillRectangle (Greenbrush, 30, 30, 150, 70);

g.compositingquality = compositingquality.gammacorrected;

G.drawimage (BM2, 300, 200);
Base. OnPaint (e);

}

10. Anti-aliasing

protected override void OnPaint (PaintEventArgs e)

{

Graphics g = e.graphics;

Zoom in 8 times times

G.scaletransform (8, 8);

No anti-aliasing graphics and text

Draw (g);

Set anti-aliasing

G.smoothingmode = Smoothingmode.antialias;

Move Right 40

G.translatetransform (40, 0);

That's after the anti-aliasing.

Draw (g);
Base. OnPaint (e);

}
private void Draw (Graphics g)

{

Draw graphics and text

G.drawline (Pens.gray, 10, 10, 40, 20);

G.drawellipse (Pens.gray, 20, 20, 30, 10);

string s = "anti-aliasing test";

Font font = new Font ("Arial", 5);

SolidBrush brush = new SolidBrush (Color.gray);

g.DrawString (S, font, brush, 10, 40);

}