1. Ch 8 2D Graphics Author: Tony

2. QPainter

Point

drawPoint

3. drawPoints Line

drawLine

4. drawLines PolyLine

drawPolyLine

5. QPainter (cont.)

drawPolygon

6. drawRect 7. drawRoundRect 8. drawEllipse 9. QPainter (cont.)

drawArc

10. drawChord 11. drawPie 12. QPainter (cont.)

DrawText

13. DrawPixmap 14. DrawPath 15. Three Main Painter Setting

pen

Drawing lines and shape outlines

brush

Filling geometric shape

font

Drawing text

16. QPainterPath

Specify the arbitrary vector shapes

17. Workflow of Painting Path

Create Painter object and PainterPath object

18. Set render hint 19. Set painter path 20. Set painter setting for Painter object 21. Draw the path 22. Pen Style 23. Cap Style 24. Join Style 25. Brush Style 26. Gradient Fills

Linear

27. Radial 28. Conical 29. 30. Antialiasing 31. Antialiasing (cont.) 32. Window-Viewport Mechanism

Make the drawing code independent of the size or resolution of the paint device

33. Convert the logical coordinates into physical coordinates

painter.setWindow(-50, -50, 100, 100)

34. World Transformation

Multiple transformation

Applied in the order in which they are given

How many transformations?

Translate

35. Scale 36. Rotate 37. Shear (ref. to Affine Transformations) 38. World Transformation (cont.) 39. Reuse the Transformation

QTransform

40. QTimer Class

Provide repetitive and single-shot timers

41. How to use it?

Create

42. Connect its timeout() signal to the slots 43. Callstart() Result

Emit thetimeout()signal at constant intervals

44. QTimer Class (cont.)

An example,

45. QDateTime Class

Provides date and time functions

46. For example,

date()

47. time() 48. currentDateTime() Use of Gregorian and Julian Calendars 49. Rendering with QImage

Rely on platform's native paint engine

50. Accuracy is more important than efficiency

QImage

51. How to paint by Qt's platform-independent graphics engine?

Step by step

Create a QPainter to draw on the image

52. Perform the drawing using the QPainter 53. QPainter object (image) -> widget Exception

Font rendering

54. How to paint by Qt's platform-independent graphics engine? (cont.) Initializes the painter's pen, background, and font 55. Composition Mode

Default

CompositionMode_SourceOver

56. Graphics View

QGraphicsScene

Provides a surface for managing a large number of 2D graphical items

QGraphicsItem

The base class for all graphical items in a QGraphicsScene

QGraphicsView

provides a widget for displaying the contents of a QGraphicsScene

57. Graphics View (cont.) 58.

QGraphicsScene

Three layers

Background, Item, Foreground

QBrushes

Background, Foreground

59. Grouping Items

Two ways

Make an item a child of another item

60. QGraphicsItemGroup 61. QGraphicsView 62. QgraphicsView's Render Engine

Default

Qt's build-in 2D paint engine

Optional

setViewport (OpenGL)

63. Coordinate System

Viewport

Inside the QGraphicsView

Scene

Logical coordinate (positioning top-level items on the scene)

Item

Specific to each item

64. Coordinate System (cont.)

In practice, we only care about the scene coordinates and item coordinates

65. QGraphicsItem

Every item has an(x,y)position and azvalue

66. Q_DECLARE_TR_FUNCTIONS

A class is not a QObject subclass

67. Want to use thetrfunction 68. itemChange

ItemChange : Qvariant

GraphicsItemChange change

69. const QVariant &value A handler for updating the item's change 70. Callupdate()to schedule a repaint 71. prepareGeometrychange()

Call it before doing anything will affect the item's bounding rectangle

72. Ex:setText() 73. ItemChange (cont.) 74. QGraphicsItem::boundingRect()

boundingRect () : const QrectF

pure virtual

Called by QGraphicsView 75. whether the item needs to be re-drawn 76. QGraphicsItem::shape ()

shape() : QPainterPath

virtual

Called by QGraphicsView 77. Used to

Collision detection

78. Hit test 79. Select the Multiple Items

Use thectrl+click

80. QGraphicsView::RubberBandDrag

Dragging a rubber band over all items you want to select

81. Z-order of Views

sendToBack()

82. bringToFront() 83. Change the Color

Qt's build-in dialog

QColorDialog::getcolor()

When the link is changed, callupdate() 84. QColor::name()

Get the color string in#RRGGBBformat

85. Zoom Factor

QstyleOptionGraphicsItem class

A floating-point value represents as zoom factor

86. Describe the parameters needed to draw a QGraphicsItem 87. Animation Effect

QGraphicsItemAnimations

88. QTimeLine

Reimplement theQObject::timeEvent()

89. Printing

QPrinter::setPrintProgram()

90. PDF format

setOutputFormat(QPrinter::PdfFormat)

Print the entire scene

QGraphicsView::render()

Multiple pages printing

Paint one page

91. callnewPage()to advance to the next page Print the range

fromPage()-toPage()

92. Printing (cont.)