Ebook On Drawing Pencil Portraits
This book begins with four introductory chapters. Starting with Chapter 5 (which shows you how to draw lines and curves) and continuing through Chapter 24 (on the Windows clipboard), the chapters alternate between graphics topics (odd-numbered chapters) and user interface topics (even-numbered chapters).
Let's consider how to create this Decorator. Design Patterns suggests that Decorators should be derived from some general Visual Component class and then every message for the actual button should be forwarded from the decorator. In VB6, this is impractical, because it is not possible to create a new visual control that contains an existing one. Further, even if we derived a control from an existing one, it would not have the line drawing methods we need to carry out decoration.
Many of the drawing methods defined by the System.Drawing.Graphics object require you to specify the position or area in which you wish to render a given item. For example, the DrawString() method requires you to specify the location to render the text string on the Control-derived type. Given that DrawString() has been overloaded a number of times, this positional parameter may be specified using an (x, y) coordinate or the dimensions of a rectangle to draw within. Other GDI+ type methods may require you to specify the width and height of a given item, or the internal bounds of a geometric region.
Visual Basic 6.0 provides a number of graphics methods for drawing lines and shapes on a form. It also provides the PictureBox and Image controls, which allow you to apply drawing methods on other controls. There are several changes to how drawing operations are performed in Visual Basic .NET. The next sections describe these changes. You can replace Shape controls with drawing methods in the Paint event. This strategy can be used for any Shape control, but it is mandatory for oval and circle Shape controls. The following code example demonstrates how to draw a circle in Visual Basic .NET.
Because we'll need to hide and redraw the block every time these methods are called, we can reduce the calling overhead by creating a new shared property on the GameField class, the winHandle used in the preceding code , and the handle of the pictureBox used as the game field on the form. With this approach, we can set this poopeoty in the New method and use it for every drawing operation, instead of passing the handle as a parameter to the drawing methods every time its called.
You'll find that Microsoft spent a lot more time working on the Direct3D library than the DirectDraw library in DirectX 8.1 for good reason. Most, if not all, game programming now uses 3D drawing techniques. CAD and other engineering and scientific disciplines also rely on 3D drawing techniques. About the only area where 2D still reigns supreme is business graphics and only because many business graphics still have to appear in print. Eventually, business graphics will also use 3D drawing techniques. The following list provides a quick overview of some of the 3D drawing additions for DirectX 8
With the System.Drawing namespace, you can manipulate bitmaps and use various structures for dealing with graphics such as Point, Size, Color, and Rectangle. Also included are numerous classes for use in drawing logic. The first three such classes you need to understand represent the surface on which drawing takes place, and the objects used to draw lines and fill shapes
After creating a Graphics object, you can use it to draw lines, fill shapes, draw text, and so on. The major objects that you use in association with the Graphics object are the following. Pen Used to draw lines and polygons, including rectangles, arcs, and pies. Font Used to describe the font used to render text.
Readable by programs that know only the ANSI character set. There's even another text encoding known as OEM text that dates back to the character-mode environment of MS-DOS. OEM stands for original equipment manufacturer, but in the United States, it really refers to the 8-bit character set IBM used in the original PC. (You may remember the line-drawing characters used by character-mode programs.) ANSI text and OEM text differ in the upper 128 characters.
Pens are used to draw lines when you use the shape or curve drawing methods from the Graphics class. You can retrieve a standard pen using one of the static properties from the System.Drawing.Pens class, as shown below. These pens all have a width of 1 they differ only in their color.
Notice how the structure of the code has changed and how the quantity of drawing methods has increased. The .NET Framework provides more control and power over the drawing operations, but from the upgrade point of view, it has a learning curve, and the manual reimplementation of all the printing functionality can consume extensive resources. The second upgrade approach involves the creation of your own Printer class. This allows you to consolidate several drawing methods and collections of graphical objects (such as Circle or Line) and to store the coordinates that will be used to print these objects when the Print method or the EndDoc method is called. When the Print method of the PrintDocument class is called, the PrintPage event is raised. This event can be used to signal the application to draw all the objects and text stored in the collections of your PrinterClass. The following Visual Basic .NET code provides a small demonstration of how this Printer class can be developed.
The CreateRegion method in Example 5-7 creates a region in the shape of an ellipse sized to fill the client area of the control. To create nonrectangular regions, you must instantiate a GraphicsPath object, use the drawing methods of the GraphicsPath class to define a complex shape within the GraphicsPath object, and then instantiate a Region object, initializing it from the GraphicsPath object. Example 5-7 calls the GraphicsPath class's AddEllipse method to create an ellipse within the GraphicsPath object. Additional methods could be called to add more shapes (including line-drawn shapes) to the GraphicsPath object. The OnResize method in Example 5-7 ensures that the control's Region property is reset every time the control is resized. Figure 5-35 shows the control after it has been placed on a form in design mode in the Windows Forms Designer. Note that the grid dots now show through the corners of the control. This clipped area is no longer considered part of the control. If the...
Chapter 6, Create Graphics and Multimedia, shows you how to add graphics commands to your application. This chapter shows you how to draw lines, shapes, and text, in various fills and patterns. This chapter shows you how to build a custom shape and apply it to the form to make a custom-shaped form of any dimension or shape. Chapters 7, Work with Classes, and 8, Using Advanced OPP Techniques illustrate how to build and use classes
String comparisons are based on the Unicode values of the characters in the string. As discussed in Module 4 , for the English language, the character set adopted by ANSI (American National Standards Institute) and ASCII (American Standards Committee for Information Interchange) use the numbers 0-255 to cover all alphabetical characters (upper- and lowercase), digits and punctuation marks, and even characters used in graphics and line drawing. Since 255 characters is not sufficient for all of the different alphabets used in this wide world, the Unicode standard was adopted, permitting (in Visual Basic .NET) potentially 65,536 different characters. However, the values of commonly used characters are the same in ASCII and Unicode. Table 6-2 lists the ASCII values of commonly used characters.
Where color is an object of type Color. You can also take advantage of the Pens class, which contains 141 static read-only properties that return Pen objects. Pens.HotPink is thus an acceptable first argument to line-drawing methods (although appropriate only when used in moderation). A complete list of these color names is available on the inside back cover of this book.
The coordinates you pass to the various drawing methods implemented in the Graphics class are said to be world coordinates. World coordinates are first subjected to the world transform, which is the thing we've been playing around with by calling TranslateTransform, ScaleTransform, and RotateTransform. I'll formalize the world transform shortly.
WPF's composition model supports elements of any shape, and allows them to overlap. It also allows elements to have any mixture of partially and completely transparent areas. This means that any given pixel on-screen may have multiple contributing visible elements. Moreover, WPF uses anti-aliasing around the edges of all shapes. This reduces the jagged appearance that simpler drawing techniques can produce on-screen, resulting in a smooth-looking image. Finally, the composition engine allows any element to have a transformation applied before composition.
All the classes of GDI are contained in the System.Drawing namespace class. The methods to draw lines, rectangles, ellipses, arcs, and text are defined in the System.Drawing.Graphics class. Some of the important methods used in the Graphics class are as follows All of these methods use a System.Drawing.Pen object to draw on the screen. You use the pen object to draw lines and curves, but the Pen class cannot be inherited. You can use any of the colors defined in the System.Drawing.Color class to specify colors while specifying a Pen object. Alternatively, you can also use an overloaded constructor that accepts a System.Drawing.Brush object. To specify the coordinates and the bounding rectangle, you can use the System. Drawing.RectangleF structure. All the coordinate points are specified as Single.
GDI+ Pen types are used to draw lines between two end points. However, a Pen in and of itself is of little value. When you need to render a geometric shape onto a Control-derived type, you send a valid Pen type to any number of render methods defined by the Graphics class. In general, the DrawXXX() methods are used to render some set of lines to a graphics surface and are typically used with Pen objects.
So you have your drawing surface, now you need an instrument or two to draw with. If you want to draw lines and curves, the first class with which you'll need to become familiar is the Pen class. A Pen object contains all of the properties necessary to draw a line in a certain width, color, and style (dotted, dashed, and so on). There are two ways to instantiate a Pen object. The first is to use the New operator as you would for any other object, passing the desired color of the pen in as the first parameter
On line 15, the entire image is painted white using the FillRectangle method of the Graphics class. Keep in mind that the Graphics class contains the various functions to draw lines, rectangles, ellipses, and other geometric shapes. All these functions require either a Pen or Brush instance, depending on whether a line or filled image is being drawn. On line 17 another rectangle is drawn with the FillRectangle method, this one serving as the backdrop for the graphed data. For more information on the FillRectangle method (or for information on the Brush and SolidBrush classes), be sure to refer to the .NET Framework Documentation.
The Pen class enables you to draw lines and curves on a graphics surface. The namespace that contains the features used by the Pen and Brush classes is the System.Drawing.Drawing2D namespace, so be sure to add this with the using statement in your class files. By setting various properties on an instance of a Pen, you can alter the outcome of the pen display. By calling methods in the Graphics class, you can dictate the type of shape you want to output.
Coordinates you pass to the Graphics drawing methods are page coordinates. (This assumption isn't quite true, as you'll see later in this chapter, but it is true if you're setting only the PageScale and PageUnit properties.) You can represent a point in page units as (xpage, page).
It's also worth noting that you can create a pen that draws using the fill style of a brush. This technique allows you to draw lines that are filled with gradients and textures. To do so, begin by creating the appropriate brush, and then create a new pen. One of the overloaded pen constructor methods accepts a reference to a brush that's the one you need to use for a brush-based pen. The rendering quality for international text has been improved regularly. As a result, GDI draws better quality text than GDI+ when using these complex scripts. Similarly, if the Windows operating system is updated to support new languages, the GDI drawing methods will draw these scripts correctly while GDI+ likely will not, even with the correct font.
The dimensions of a form's client area are available from the ClientSize property. These dimensions are always in units of pixels. If you set a new page transform, you probably want the dimensions of the client area not in units of pixels but in units corresponding to what you're now using in the drawing methods.
The Graphics class also provides several methods for drawing specific shapes, images, or text. Most of these methods begin with the word Draw. All shape-drawing methods draw outlines using a given pen you need to use the corresponding Fill method to paint an interior fill region with a brush. Table 7-3 lists both types of methods. Keep in mind that many of these methods provide multiple overrides that accept different combinations of information.
Represents an object used to draw lines and curves. A pen can draw a line in any color and specify various styles such as line widths, dash styles, and ending shapes (such as arrows). For example, the Graphics.DrawRectangle method uses a pen to draw the outline of a rectangular area on a drawing surface.
FlatStyle allows you to choose between standard button rendering and two more unusual modes. If FlatStyle is set to FlatStyle.Popup, the button is given a thin etched border that appears to become raised when the mouse moves over the button. If FlatStyle is set to FlatStyle.Flat, the FlatAppearance settings take over. They specify the width of the border, its color, and the background color that should be employed when the user moves the mouse over the button and presses it. Overall, the results are far from impressive, and a better choice is to use the custom button-drawing techniques covered in Chapter 23.
Most of the other Graphics drawing methods don't involve Color arguments. When you draw lines or curves (which you'll start doing in Chapter 5), you use an object of type Pen, and when you draw filled areas and text, you specify an object of type Brush. Of course, pens and brushes themselves are specified using color, but other characteristics are often involved as well.
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