Friday, February 22, 2013

Graphical Device Interface (GDI)

GDI (Graphical Device Interface):
It contains several functions, data type, structure and macro. GDI provide function to draw line rectangle, image, GDI also supports colour capability.
The GDI functions:
                                                        i.            Functions that get (create) and release (destroy) a device context.
                                                      ii.            Functions that obtain information about the device context.
                                                    iii.            Function that draw something.
                                                   iv.            Function that work with GDI Object.

TextOut:
TextOut(hdc,x,y,string,iLength);

To point client area of window, we use windows “Graphical Device Interface” (GDI) functions for writing text string, rectangle, ellipse, begin point & end point to the client area of window.
For e.g.:
TextOut(hdc,x,y,PSText,iLength);
                                                       I.            PSText:
The PSText argument is a pointer to the character string.
                                                     II.            iLength:
The length is a length of the string in character.
                                                  III.            x,y:
The x and y define the starting position of the character string in the client area.
                                                  IV.            hdc:
The hdc argument is a “handle to a device context”.




The GDI Primitive:
1.     Line & Curve:
To draw any shape in the system area, we use line and curve for rectangle, arc, ellipse these are the examples.
2.     Filled area:
Whenever a series of line or curve enclose an area, we can fill it with current GDI Brush Object.
3.     Bitmap:
A bitmap is a rectangular array of bits.
4.     Text:
This is not very easy to draw a text in graphics. Windows 3.1 GDI began supporting fonts.


Some other GDI functions:
Rectangle(hdc,x,y,x1,y1)
Ellipse(hdc,left,iTop,Right,Bottom)
RoundRect(hdc,left,top,right,bottom,width,height)
SetTextColor(hdc,RGB(0,0,0))
SetBkColor(hdc,RGB(0,0,0))


Device Context:
The GDI function always contains the handle to the device context. The device context is also referred as DC. The device context is a data structure associated with particular window.
The window application generally use two method for getting a device context handle for painting screen –
1.     Case WM_PAINT:
      hdc=BeginPaint(hwnd, &PS);
                  [Use GDI Function]
                  EndPoint(hwnd, &PS);
      break;
2.     Case WM_PAINT:
      hdc=GetDC(hwnd);
                  [Use GDI Function]
                  ReleaseDC(hwnd,hdc);
      break;


Child Window Control:
When one window has control in the form child window, these components of the windows are called as child window control. The various control can be placed on the main window, these control build user friendliness in the program. These child window control respond to mouse & keyboard events.

0 comments:

Post a Comment

Powered by Blogger.