一个优秀的C#开源绘图软件 DrawTools

1、Extensions to DrawTools

Author

Mark Miller
I develop software for a leading healthcare system in Northern Illinois.

Download updated demo - 55.57 KB

Download (VS 2010) updated source - 889.43 KB

Introduction

Alex Fr provided an excellent set of drawing tools in his DrawTools article and these tools serve as a basis for this article, which expands on the original toolset in the following ways:

In addition to the basic Rectangle, Ellipse, Line and Scribble tools, this version adds PolyLine, Filled Ellipse, Filled Rectangle, Textand Imagetools

Multiple drawing Layers

Zooming

Panning

Rotation

In this article, I will describe how Layerswere implemented, as well as the Textand Imagetools.

Background

See the original DrawTools article for details on how the basic application is built, class structure, etc.

It is also assumed that the reader has a working understanding of GDI+ fundamentals, including Matrices. For an excellent introduction to GDI+, see www.bobpowell.net.

Implementing Layers

Adding Layersto the application involved adding two classes,

Layer

and

Layers

, where

Layer

defines a single

Layer

and

Layers

defines the collection of

Layers

in an

ArrayList

.

Each

Layer

exposes the following properties:

private string _name;
private bool _isDirty;
private bool _visible;
private bool _active;
private GraphicsList _graphicsList;

Note that the

Layer

contains the

GraphicsList

- this is the key to the whole thing - each

Layer

contains its own list of drawing objects instead of

DrawArea

.

DrawArea

is modified to declare a

Layers

collection instead of a

GraphicsList

collection:

// Define the Layerscollection
private Layers_layers;

When

DrawArea

is initialized, the

Layers

are initialized by creating the first

Layer

and setting it

Active

and

Visible

:

public DrawArea()
{
// create list of Layers, with one default active visible layer
_layers = new Layers();
_layers.CreateNewLayer("Default");
_panning = false;
_panX = 0;
_panY = 0;
// This call is required by the Windows.Forms Form Designer.
InitializeComponent();
}

In the

Layers

class, the

CreateNewLayer()

method actually creates the new

Layer

:

/// <summary>
/// Create a new layer at the head of the layers list and set it
/// to Activeand Visible.
/// </summary>
/// <param name="theName">The name to assign to the new layer</param>
public void CreateNewLayer(string theName)
{
// Deactivate the currently active Layer
if(layerList.Count > 0)
((Layer)layerList[ActiveLayerIndex]).IsActive= false;
// Create new Layer, set it visible and active
Layerl = new Layer();
l.IsVisible = true;
l.IsActive= true;
l.LayerName = theName;
// Initialize empty GraphicsList for future objects
l.Graphics = new GraphicsList();
// Add to Layerscollection
this.Add(l);
}

Note that any one or all

Layers

can be visible at the same time, but only one

Layer

may be active at any time.

You can control the

Layers

in the sample application by clicking on the Current

Layer

: name at the bottom of the application window - Click on the name ("

Default

") to open the

Layers

dialog:



From this dialog, you can Add new

Layers

, change the names of the

Layer

(s), and change the

Layer

(s) visibility and which

Layer

is

Active

. The "New Layer" column is checked whenever you click the "Add Layer" button. To delete Layer(s), simply check the "Deleted" column and close the dialog with the "Close" button. Remember only one Layermay be active at any one time. You will be reminded of this if you attempt to have more than one

Layer

active. Also note the Active

Layer

must be

Visible

.

When the application runs, each object that is drawn is added to the

GraphicsList

maintained by the active

Layer

. Note this relationship is preserved through saving and re-opening a drawing file.

Layerscome in very handy when you want to draw "on top of" another image. For example, the image at the top of this article contains two layers. The following image shows the same picture with the Background Layerturned off:



Here is the same drawing with the Drawing Layerinvisible and the Background Layervisible:



Objects on Layerswhich are visible but not active cannot be selected, moved, deleted, etc.

Each drawing object is added to the correct

Layer

by the

AddNewObject()

method in the

ToolObject

class:

protected void AddNewObject(DrawAreadrawArea, DrawObject o)
{
int al = drawArea.TheLayers.ActiveLayerIndex;
drawArea.TheLayers[al].Graphics.UnselectAll();
o.Selected = true;
o.Dirty= true;
drawArea.TheLayers[al].Graphics.Add(o);
drawArea.Capture = true;
drawArea.Refresh();
} 

Implementing Zooming, Panning, and Rotation

Zooming, Panning, and Rotation are implemented by adding a few variables and some code to the

MainForm

and

DrawArea

classes.

Zooming is controlled by buttons on the form, and also by the mouse wheel when Ctrl is held down.

Pan is controlled by the Hand button on the form, and can be cancelled by a right-click.

Rotation is controlled by buttons on the form - note Rotation affects the entire drawing.

Here is an example of all three in use:



The heart of this code is the

BackTrackMouse()

method, which takes the "apparent" mouse position and converts it to a valid point based on the current Zoom level, Pan position, and Rotation:

/// <summary>
/// Back Track the Mouse to return accurate coordinates regardless of
/// zoom or pan effects.
/// Courtesy of BobPowell.net <seealso cref="http://www.bobpowell.net/backtrack.htm"/>
/// </summary>
/// <param name="p">Point to backtrack</param>
/// <returns>Backtracked point</returns>
public Point BackTrackMouse(Point p)
{
// Backtrack the mouse...
Point[] pts = new Point[] { p };
Matrix mx = new Matrix();
mx.Translate(-this.ClientSize.Width / 2, -this.ClientSize.Height / 2,
MatrixOrder.Append);
mx.Rotate(_rotation, MatrixOrder.Append);
mx.Translate(this.ClientSize.Width / 2 + _panX, this.ClientSize.Height / 2 +
_panY, MatrixOrder.Append);
mx.Scale(_zoom, _zoom, MatrixOrder.Append);
mx.Invert();
mx.TransformPoints(pts);
return pts[0];
}

This routine comes from Bob Powell's excellent website. Through the use of the GDI+ Matrix class, the mouse point passed to this method is moved (Translate), Rotated, and Scaled based on the current PanX, PanY, Zoom, and Rotation values. The important thing to remember is that anytime you need to determine where the mouse pointer actually is in your drawing, you must call this method. You will see this method used throughout the program in the

DrawArea

class as well as others. An example of its usage is shown here:

private void DrawArea_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
lastPoint = BackTrackMouse(e.Location);
if (e.Button == MouseButtons.Left)
tools[(int)activeTool].OnMouseDown(this, e);
else if (e.Button == MouseButtons.Right)
{
if (_panning == true)
_panning = false;
ActiveTool = DrawArea.DrawToolType.Pointer;
}
//OnContextMenu(e);
}

The current zoom level is controlled by the following simple routine:

private void AdjustZoom(float _amount)
{
drawArea.Zoom += _amount;
if (drawArea.Zoom < .1f)
drawArea.Zoom = .1f;
if (drawArea.Zoom > 10)
drawArea.Zoom = 10f;
drawArea.Invalidate();
SetStateOfControls();
}

Then in the

DrawArea.Paint()

method, the zoom, pan, and rotation values are used to alter the way the canvas is painted:

private void DrawArea_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
Matrix mx = new Matrix();
mx.Translate(-this.ClientSize.Width / 2, -this.ClientSize.Height / 2,
MatrixOrder.Append);
mx.Rotate(_rotation, MatrixOrder.Append);
mx.Translate(this.ClientSize.Width / 2 + _panX, this.ClientSize.Height / 2 +
_panY, MatrixOrder.Append);
mx.Scale(_zoom, _zoom, MatrixOrder.Append);
e.Graphics.Transform = mx;

SolidBrush brush = new SolidBrush(Color.FromArgb(255, 255, 255));
e.Graphics.FillRectangle(brush,
this.ClientRectangle);
// Drawobjects on each layer, in succession so we get the correct layering.
// Only draw layers that are visible
if (_layers != null)
{
int lc = _layers.Count;
for (int i = 0; i < lc; i++)
{
if(_layers[i].IsVisible == true)
if(_layers[i].Graphics != null)
_layers[i].Graphics.Draw(e.Graphics);
}
}
DrawNetSelection(e.Graphics);
brush.Dispose();
}

Update - 8/25/2007 - Individual Object Rotation & Bug Fixes

The primary advancement in this update is the ability to rotate individual objects - when one or more objects are selected, clicking the Rotate tools will rotate those objects instead of the entire drawing surface.

There is one caveat, however - the selection rectangle for the rotated object is not rotated - if someone can help with this, I would greatly appreciate it!

This update also includes several small bug fixes reported by users - thanks to all for reporting!

History

3/6/2007

Original article uploaded to The Code Project

3/6/2007

Updated to include more information on zoom/pan/rotation

8/25/2007

Updated Individual Object Rotation

9/27/2007

Added the missing links to the new source code

12/23/2009

Added Tooltip control which appears when mouse is over an object. Tooltip displays the Center coordinates of the object for

Rectangle

,

Ellipse

and

Image

objects. For other objects, Tooltip displays starting and ending coordinates.

Text

objects do not display Tooltip.
This was implemented adding the Tooltip control to the

ToolPointer

class. Each

Draw

Object fills the

TipText

property and the

MouseMove

event in

ToolPointer

controls
when the Tooltip is displayed and removed from the canvas. This
implementation is not perfect, as the Tooltip flashes when displayed so
is meant as an example of one way information about the object can be
displayed.
Perhaps a better way to do this would be to display
information about the object in a separate "Information Window" and then
only when the object is selected.

See the new source code for details.

6/23/2010

Updated project to include object ordering fix that corrects the way objects are stacked when a file is opened

Updated project to Visual Studio 2010

See the new source code for details

10/4/2011

Corrected several issues with Layersand layering

2、DrawTools 2014

Author

Arnault Bonafos, 16 Jan 2014

Download source - 85 KB

Download binaries - 37.9 KB

Introduction

Current alternative is based on the CodeProject DrawTools 2005, built under Visual Studio C# 2010.

The main goal of this tip is to post and save the DrawTools project back to the community after some enhancements. The tip is short, as the improvements are minor.

A few improvements have been made, as follows:

Add scroll bars to the draw area

Handling of

AutoScrollPosition

in the different tools provided by the original project

Export of the drawing with jpeg format

Background

Knowledge of C# is required, but this project shows the basics of UI programming under '.NET'.

Architecture

Dynamic handling for showing scroll bars

A dirty boolean is handled in

GraphicsList

, the canvas document, where it should be. To this

Dirty

property is associated a

DocumentDirtyObserver

interface.

Hide Copy Code

public interface DocumentDirtyObserver
{
void IsDirty(GraphicsList gList);
}

Every time the document is modified, look with the different draw tools, its

Dirty

property is set to

true

and any

DocumentDirtyObserver

is fired.

Hide Copy Code

public bool Dirty
{
get
{
return this.dirty;
}
set
{
this.dirty = value;
if (this.dirty)
{
NotifyDirty();
}
}
}

The class

DrawArea

implements the

DocumentDirtyObserver

, and every time the document is '

dirty

', it calls

AdjustRendering

, which in turn computes the bounding box of the canvas document (

GraphicsList

).

Hide Copy Code

void AdjustRendering()
{
Size docSize;

if (this.GraphicsList != null)
{
docSize = this.GraphicsList.GetSize();
docSize.Width += 20;
docSize.Height += 20;
AutoScrollMinSize = docSize;
}
else
{
AutoScrollMinSize = new Size(0, 0);
}
Invalidate();
}

This way, it implements the Mode/View/Controller design pattern, the

GraphicsList

being the model,

DrawArea

being the View and the draw

Tools

being the controller.

In the future,

Dirty

property should be handled in only one place (it is also handled in the

DrawArea

class).

Export the graph to JPEG format

The DrawTools 2014 architecture is good enough to be followed to implement a new menu strip option.

Add a menu item to the menu bar

Simply open the MainFormdesigner and add the option

Link the

MenuItem

to a

MainForm

method to trigger the

CommandExportToJpg

Hide Copy Code

private void CommandExportToJpg()
{
docManager.ExportToJpg();
}

Implement the user interface logic in the

DocManagerExportToJpg

I let you look at the

DocManager.ExportToJpg

Subscribe

MainFormExportEvent

method implementation to

DocManager

event.

Hide Copy Code

docManager.ExportEvent += docManager_ExportEvent;

Implement

MainForm

logic to actually transform image bitmap into JPEG file.
All is in the source code, I don't copy it here as it is essentially technical stuff.

Result

The result is best shown by the following graph, obtained with a customized version of the DrawTools.

Points of Interest

Architecture is already well thought in the original project, please read the original document for insight about it.

DrawTools 2005

There was a bug where the status bar was hiding the horizontal scroll bar, but after some thorough inspection of the code, it has been fixed.

Issue on Stackoverflow

History

Added scroll bars to the draw area

Added a status bar

Fixed a bug on the context menu when the scroll bar position is not 0

Export of the drawing with jpeg format

Fixed an

OutOfMemoryException

with JPEG format export

Special thank you to Alex, who originally posted the DrawTools project on CodeProject.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)