Learning to Draw Basic Graphics

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Learning to Draw Basic Graphics
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Graphics Essentials

• Graphics Coordinate System
• Windows coordinate system origin at upper-left
  corner, x values increasing to the right and y
  values increasing down
• Drawing area client area
• Basics of Color
• RGB
• COLORREF green RGB(0, 255, 0)
• Intensities of each component range from 0 to 255
  
• Windows colors determined by the combination of
  the intensities of the RGB

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GDI (Graphics Device Interface)

• Provide an interface between drawing operation
  and graphics driver

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GDI Component Device Context

• Device Context
• A gate way to a physical graphics device
• All drawing is actually done to a device context
• Through DC, drawing can be done with GDI
• Two ways to obtain DC

• PAINTSTRUCT ps
• HDC hDC BeginPaint(hWindow, ps)
• // returns a handle to a device context
• GDI drawing operations go here
• EndPaint(hWindow, ps)
• // release the device context

• HDC hDC GetDC(hWindow)
• GDI drawing operations go here
• ReleaseDC(hWindow, hDC)

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Graphics components in GDI

• Pens
• Draw lines and curves
• Brushes
• Paint the interior of polygons, ellipses, and
  paths
• Bitmaps
• A graphical image stored as an array of pixels
• Can be 1 bit per pixel to 32 bits per pixel
• 8 bits per pixel 256 color bitmaps, 24 bits per
  pixel 224 color bitmaps
• Palettes
• A set of colors used by the GDI when rendering a
  bitmap

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Painting Windows

• In WndProc( ) function
• case WM_PAINT
• hDC hDC
• PAINTSTRUCT ps
• hDC BeginPaint(hWindow, ps)
• GamePaint(hDC) // paint the game
• EndPaint(hWindow, ps)

Void GamePaint(HDC hDC) GDI drawing
operations go here MoveToEx(hDC, 0, 0,
NULL) LineTo(hDC, 50, 50)
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Painting Windows Cont.

• Painting Text 1 approach at specified point
• Void GamePaint(HDC hDC)
• GDI drawing operations go here
• TextOut(hDC, 10, 10, TEXT(Hello World), 16)

Painting Text 2 approach within a
rectangle Void GamePaint(HDC hDC) GDI
drawing operations go here RECT
rect GetClientRect(hWindow, rect) DrawText(hD
C, TEXT(Hello World), -1, rect, DT_SINGLELINE
DT_CENTER DT_VCENTER)
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Painting Windows Cont.

• Draw line
• Void GamePaint(HDC hDC)
• MoveToEx(hDC, 10, 40, NULL)
• LineTo(hDC, 44, 10)
• LineTo(hDC, 78, 40)

Draw Rectangle Void GamePaint(HDC
hDC) Rectangle(hDC, 16, 36, 72,
70) Rectangle(hDC, 34, 50, 54, 70)
Fill Rectangle int FillRect(HDC hDC, CONST RECT
lprc, HBRUSH hbr)
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Painting Windows Cont.

• Draw Ellipse
• BOOL Ellipse(HDC hDC, int xLeft, int yTopm int
  xRight, int yBottom)

• Draw Polygon
• Void GamePaint(HDC hDC)
• POINT points3
• points0 5, 10
• points1 25, 30
• points2 15, 20
• Polygon(hDC, points, 3)

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Working with Pens and Brushes

• Creating Pens to control line
• HPEN CreatePen(int iPenStyle, int iWidth,
  COLORREF crColor)
• Ex
• HPEN hBluePen CreatePen(PS_SOLID, 1, RGB(0, 0,
  255))

• Selecting Pens
• HPEN hPen SelectObject(hDC, hBluePen)
• // do some drawing here
• SelectObject(hDC, hPen)
• DeleteObject(hBluePen)

• Creating Brushes to fill colors
• HBRUSH hPurpleBrush CreateSolidBrush(RGB(255,
  0, 255))