Is it possible to create another Graphics form an existing Graphics with a different coordinate system? For example, let's say that the black rectangle is the ClipRectangle of the Graphics object I got in OnPaint(). If I only want to draw inside the blue rectangle, I would have to constantly calculate the offset. That is, to draw at the logical point (0,0) in the blue rectangle, I would have to add the x and y offsets. That makes drawing code complicated.
Is there a way to create some sort of virtual Graphics using the Graphics above but with a different coordinate system? Something like below
//not actual code
var virtualG = Graphics.FromExistingGraphics(e.Graphics, 200/*x1*/, 200/*y1*/, 1000/*x2*/, 600/*y2*/);
//Doing the same thing as e.Graphics.DrawLine(pen, 200, 200, 400, 400)
virtualG.DrawLine(pen, 0, 0, 200, 200);
//Draws nothing, NOT the same as e.Graphics.DrawLine(pen, 1100, 200, 1200, 400)
//, because its outside of the virtualG's bounds.
virtualG.DrawLine(pen, 900, 0, 1000, 200);
I thought about creating a new Graphics using bitmap, draw there and then copy the bitmap to the specified location of the Graphics from OnPaint, but that could be slow.
If you don't want any scaling, and simply want to move the origin to (200, 200), then use TranslateTransform as suggested previously. If you want to clip any drawings outside that rectangle, then use SetClip.
Here's an example, showing the same set of lines drawn before and after translating and clipping. The black lines are before, while the blue line is after (the second blue line is clipped and therefore not visible). The red rectangle shows the clipping region:
Code:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
public class Line
{
public Point ptA;
public Point ptB;
public void Draw(Graphics G, Color color)
{
using (Pen P = new Pen(color))
{
G.DrawLine(P, ptA, ptB);
}
}
}
private List<Line> Lines = new List<Line>();
private void Form1_Load(object sender, EventArgs e)
{
Lines.Add(new Line() { ptA = new Point(0,0), ptB = new Point(200, 200)});
Lines.Add(new Line() { ptA = new Point(900, 0), ptB = new Point(1000, 200) });
}
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
Graphics G = e.Graphics;
G.Clear(Color.DarkGray);
foreach(Line line in Lines)
{
line.Draw(G, Color.Black);
}
Rectangle rc = new Rectangle(new Point(200, 200), new Size(800, 400));
G.DrawRectangle(Pens.Red, rc);
G.SetClip(rc);
G.TranslateTransform(rc.Left, rc.Top); // origin is now at (200, 200)
foreach (Line line in Lines)
{
line.Draw(G, Color.Blue);
}
}
}
Related
I add a polygon to the GraphicsPath and try to check if the rectangle is positioned inside of it. When rectangle is completely outside the polygon code responds correctly. However, when inside the polygon its return value is unpredictable.
For now I only check top-left corner of the rectangle.
private void Form1_Paint(object sender, PaintEventArgs e)
{
g = e.Graphics;
rect = new Rectangle(new Point(x, y), new Size(30,30));
g.FillRectangle(Brushes.Green, rect);
Point[] points = new Point[]
{
new Point(0, 0),
new Point(50, 0),
new Point(50, 50),
new Point(0, 50),
};
graphicsPath.AddPolygon(points);
g.DrawPolygon(Pens.Black, points);
if ((graphicsPath.IsVisible(rect.Location)))
{
this.Text = "Inside " + rect.Location.ToString();
}
else
{
this.Text = "not inside " + rect.Location.ToString();
}
}
I also have some code which is used to move the rectangle using MouseDown, MouseUp and MouseMove events.
The results I receive are:
But after repainting the form (even just minimizing window) those same coordinates are responding differently and the result is:
I'm creating a program that uses the flycapture camera. I've created a class that extends the pictureBox class in order to draw a crosshair, consisting of two lines, onto the screen. I want to be able to move the crosshair from the center to any other location on the screen.
The problem is when the form is resized, the crosshair moves to a different location as shown here. I want the crosshair to be pointing at the same part of the image as before it was resized (in the example it is no longer pointing at the grey mesh). I'm drawing the crosshair in relation to the height and width of the pictureBox. I want to be able to draw the lines on the image but the image height and width are always the same regardless of the image's size.
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace FlyCapture2SimpleGUI_CSharp
{
class IMSPictureBox : PictureBox
{
private Color colorSetting = Color.Black;
private float width = 1.0f;
public IMSPictureBox()
{
this.Paint += IMSPictureBox_Paint;
}
private void IMSPictureBox_Paint(object sender, PaintEventArgs e)
{
//Draw if image has loaded
if (this.Image != null)
{
//Draw horizontal line
e.Graphics.DrawLine(
new Pen(this.colorSetting, this.width),
new Point(0, this.Size.Height / 2 + 100),
new Point(this.Size.Width, this.Size.Height / 2 + 100));
//Draw vertical line
e.Graphics.DrawLine(
new Pen(this.colorSetting, this.width),
new Point(this.Size.Width / 2 + 100, 0),
new Point(this.Size.Width / 2 + 100, this.Size.Height));
}
}
}
}
Edit:
As DiskJunky suggested, I'm now drawing on the image itself and not using the Paint function above.
Here is the image getting set:
private void UpdateUI(object sender, ProgressChangedEventArgs e)
{
UpdateStatusBar();
pictureBox1.SetImage = m_processedImage.bitmap;
pictureBox1.Invalidate();
}
Here are the lines drawing on the image:
public System.Drawing.Image SetImage
{
set
{
using (Graphics g = Graphics.FromImage(value))
{
g.DrawLine(new Pen(Color.Red, 3.0f), new Point(0, 0), new Point(value.Width, value.Height));
g.Dispose();
}
this.Image = value;
}
get
{
return this.Image;
}
}
I now have a line that scales with the image, but now it's constantly flickering.
This isn't exact but modifying to something like the following will keep the position static as the picture box resizes;
class IMSPictureBox : PictureBox
{
private Color colorSetting = Color.Black;
private float width = 1.0f;
private Tuple<Point, Point> _verticalLine;
private Tuple<Point, Point> _horizontalLine;
public IMSPictureBox()
{
this.Paint += IMSPictureBox_Paint;
}
private void IMSPictureBox_Paint(object sender, PaintEventArgs e)
{
//Draw if image has loaded
if (this.Image != null)
{
//Draw vertical line
if (_verticalLine == null)
{
_verticalLine = new Tuple<Point, Point>(new Point(100, 0), new Point(100, this.Size.Height);
}
e.Graphics.DrawLine(
new Pen(this.colorSetting, this.width),
_verticalLine.Item1,
_verticalLine.Item2);
//Draw horizontal line
if (_horizontalLine == null)
{
_horizontalLine = new Tuple<Point, Point>(new Point(0, 100), new Point(this.Size.Width, 100);
}
e.Graphics.DrawLine(
new Pen(this.colorSetting, this.width),
_horizontalLine.Item1,
_horizontalLine.Item2);
}
}
}
Edit
The above solution outlines the concept of preserving the line position. As per discussion in comments below, this developed into a more involved solution for the OP as additional requirements came out of investigating and testing the solution above for the original intent - to cleanly draw a a coordinate marker on an image.
To that end a manual double buffering mechanism is recommended in that scenario as the PictureBox control supports limited drawing capability itself. An example of manually implementing a double buffering solution can be found here; https://learn.microsoft.com/en-us/dotnet/framework/winforms/advanced/how-to-manually-render-buffered-graphics
Rather than calling DrawEllipse() there'll be calls to DrawLine() to display the coordinate marker. One caveat is that if the image is still being displayed in the PictureBox then the PictureBoxSizeMode.Zoom value may still have to be accounted for.
I've an oval picturebox (Code below). I want to add a border around the picturebox. I allready tried to add a second rect but this only made my region smaller. Is there any way to make a border?
using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;
class OvalPictureBox : PictureBox
{
public OvalPictureBox()
{
}
protected override void OnResize(EventArgs e)
{
base.OnResize(e);
using (var gp = new GraphicsPath())
{
gp.AddEllipse(new Rectangle(0, 0, this.Width - 1, this.Height - 1));
this.Region = new Region(gp);
}
}
private void InitializeComponent()
{
((System.ComponentModel.ISupportInitialize)(this)).BeginInit();
this.SuspendLayout();
//
// OvalPictureBox
//
((System.ComponentModel.ISupportInitialize)(this)).EndInit();
this.ResumeLayout(false);
}
}
EDIT
I figured it out. I just draw an ellipse in the picturebox.
float penWidth = 5F;
Pen myPen = new Pen(Color.FromArgb(242, 141, 1), penWidth);
e.Graphics.DrawEllipse(myPen, new RectangleF(new PointF(0, 0), new
SizeF((float)(portraitPicture.Width - 1), portraitPicture.Height - 1)));
myPen.Dispose();
Is there a cleaner or better way? Or is this the best way?
Just draw ellipse that is bigger than the one you already have. But this ellipse should be drawn first, otherwise it would cover the other ellipse.
How much should it be bigger? Border width :)
I'm just starting to learn the GDI+ system for drawing lines, circles etc. I've created a component (scanner) that inherits a Panel to draw on (not sure if panel or picture box is best).
On the "Scanner" Im currently drawing a circle on it. the component can be added to a winform and using docking will resize when the winform resizes. At the moment I'm getting the size of the component to calculate the size of the circle but what I want to do is basically say no matter what size the component is the "canvas" is always 300 x 300 wide, so I can say the circle should be positioned at 25,25 with a size of 250x250.
As you might guess from the name "Scanner" I want to plot points on it, but these will be calculated from the center (150,150) location.
Below is the code I have that basically draws the circle.
Many thanks for any help on this.
public partial class Scanner : Panel
{
public Scanner() {
InitializeComponent();
this.DoubleBuffered = true;
}
protected override void OnPaint(PaintEventArgs e) {
Graphics g = e.Graphics;
Draw(g);
base.OnPaint(e);
}
protected override void OnResize(EventArgs e) {
Graphics g = this.CreateGraphics();
Draw(g);
base.OnResize(e);
}
private void Draw(Graphics g) {
g.Clear(Color.Black);
g.PageUnit = GraphicsUnit.Pixel;
Pen green = new Pen(Color.Green);
Font fnt = new Font("Arial", 10);
SolidBrush sb = new SolidBrush(Color.Red);
int pos = (this.Width < this.Height ? this.Width : this.Height) / 2;
int size = (int)(pos * 1.9);
pos -= ((int)size / 2);
g.DrawEllipse(green, pos, pos, size, size);
g.DrawString(this.Width.ToString(), fnt, sb, new Point(0, 0));
}
}
Based on your recent comment, I understand you want to do your drawing on a fixed-size canvas, and plot this canvas inside the control, as large as will fit in the control.
Try the code below:
public class Scanner : Panel
{
private Image _scanner;
public Scanner()
{
this.SetStyle(ControlStyles.ResizeRedraw, true);
CreateScanner();
}
private void CreateScanner()
{
Bitmap scanner = new Bitmap(300, 300);
Graphics g = Graphics.FromImage(scanner);
g.DrawEllipse(Pens.Green, 25, 25, 250, 250);
g.Dispose();
_scanner = scanner;
}
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
int shortestSide = Math.Min(this.Width, this.Height);
if (null != _scanner)
e.Graphics.DrawImage(_scanner, 0, 0, shortestSide, shortestSide);
}
}
I have this code that draws a Rectangle ( Im trying to remake the MS Paint )
case "Rectangle":
if (tempDraw != null)
{
tempDraw = (Bitmap)snapshot.Clone();
Graphics g = Graphics.FromImage(tempDraw);
Pen myPen = new Pen(foreColor, lineWidth);
g.DrawRectangle(myPen, x1, y1, x2-x1, y2-y1);
myPen.Dispose();
e.Graphics.DrawImageUnscaled(tempDraw, 0, 0);
g.Dispose();
}
But what if I want to draw a circle, what will change?
g.DrawRectangle(myPen, x1, y1, x2-x1, y2-y1);
There is no DrawCircle method; use DrawEllipse instead. I have a static class with handy graphics extension methods. The following ones draw and fill circles. They are wrappers around DrawEllipse and FillEllipse:
public static class GraphicsExtensions
{
public static void DrawCircle(this Graphics g, Pen pen,
float centerX, float centerY, float radius)
{
g.DrawEllipse(pen, centerX - radius, centerY - radius,
radius + radius, radius + radius);
}
public static void FillCircle(this Graphics g, Brush brush,
float centerX, float centerY, float radius)
{
g.FillEllipse(brush, centerX - radius, centerY - radius,
radius + radius, radius + radius);
}
}
You can call them like this:
g.FillCircle(myBrush, centerX, centerY, radius);
g.DrawCircle(myPen, centerX, centerY, radius);
Try the DrawEllipse method instead.
You'll need to use DrawEllipse if you want to draw a circle using GDI+.
An example is here: http://www.websupergoo.com/helpig6net/source/3-examples/9-drawgdi.htm
You should use DrawEllipse:
//
// Summary:
// Draws an ellipse defined by a bounding rectangle specified by coordinates
// for the upper-left corner of the rectangle, a height, and a width.
//
// Parameters:
// pen:
// System.Drawing.Pen that determines the color, width,
// and style of the ellipse.
//
// x:
// The x-coordinate of the upper-left corner of the bounding rectangle that
// defines the ellipse.
//
// y:
// The y-coordinate of the upper-left corner of the bounding rectangle that
// defines the ellipse.
//
// width:
// Width of the bounding rectangle that defines the ellipse.
//
// height:
// Height of the bounding rectangle that defines the ellipse.
//
// Exceptions:
// System.ArgumentNullException:
// pen is null.
public void DrawEllipse(Pen pen, int x, int y, int width, int height);
if you want to draw circle on button then this code might be use full.
else if you want to draw a circle on other control just change the name of control and also event. like here event button is called. if you want to draw this circle in group box call the Groupbox event.
regards
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
this.button1.Location = new Point(108, 12);
// this.Paint += new PaintEventHandler(Form1_Paint);
this.button1.Paint += new PaintEventHandler(button1_Paint);
}
void button1_Paint(object sender, PaintEventArgs e)
{
Graphics g = this.button1.CreateGraphics();
Pen pen = new Pen(Color.Red);
g.DrawEllipse(pen, 10, 10, 20, 20);
}
}
With this code you can easily draw a circle...
C# is great and easy my friend
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Graphics myGraphics = base.CreateGraphics();
Pen myPen = new Pen(Color.Red);
SolidBrush mySolidBrush = new SolidBrush(Color.Red);
myGraphics.DrawEllipse(myPen, 50, 50, 150, 150);
}
}
private void DrawEllipseRectangle(PaintEventArgs e)
{
Pen p = new Pen(Color.Black, 3);
Rectangle r = new Rectangle(100, 100, 100, 100);
e.Graphics.DrawEllipse(p, r);
}
private void Form1_Paint(object sender, PaintEventArgs e)
{
DrawEllipseRectangle(e);
}
PictureBox circle = new PictureBox();
circle.Paint += new PaintEventHandler(circle_Paint);
void circle_Paint(object sender, PaintEventArgs e)
{
e.Graphics.DrawEllipse(Pens.Red, 0, 0, 30, 30);
}