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Visual Basic Graphics

Visual Basic Graphics. Warning: The way I am using Visual Basic graphics is somewhat different (and much simpler!) to that of the book. Use these slides as you main reference. picturebox. We will change color to white. EamonnsPicBox. Note size 696 , 224.

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Visual Basic Graphics

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  1. Visual Basic Graphics Warning: The way I am using Visual Basic graphics is somewhat different (and much simpler!) to that of the book. Use these slides as you main reference.

  2. picturebox We will change color to white EamonnsPicBox Note size 696 , 224

  3. Assume that all code you see today is written here.

  4. When we run our program, we see this form, with a blank picturebox control 224 696 Almost all computer graphic systems (including VB) use an “upside down” Cartesian coordinate system…

  5. (0,0) (696,224) (102,112) 0 112 224 0 348 696 Any point in the Cartesian coordinate system is specified by a pair of numbers X and Y.

  6. (0,0) (696,224) Let us draw the line above in VB

  7. There is a built-in function that will draw a line… EamonnsPicBox.CreateGraphics.DrawLine(Pens.Blue, 0, 0, 696, 224) • The parameter list is: • The Pen object (more later) • The first points X coordinate • The first points Y coordinate • The second points X coordinate • The second points Y coordinate Note: You must click on the control to make the line appear

  8. We can draw multiple lines… EamonnsPicBox.CreateGraphics.DrawLine(Pens.Blue, 0, 0, 696, 224) EamonnsPicBox.CreateGraphics.DrawLine(Pens.Red, 0, 224, 696, 0)

  9. We can use all the VB tools we have previously learned in conjunction with the graphics tools! Dim shtLoopCounter As Short For shtLoopCounter = 0 To 224 Step 20 EamonnsPicBox.CreateGraphics.DrawLine(Pens.Blue, 0, 0, 696, shtLoopCounter) Next shtLoopCounter

  10. There is a function Rnd which produces random numbers Function Description: Returns a pseudo random decimal number that is greater than or equal to 0 and less than 1. By passing Rnd an optional numeric parameter, you can further control the type of random number you generate. Common Uses: Random numbers are required for a great many reasons. By combining the output of the Rnd function with some basic mathematics, random numbers can be generated within a given range. Review Syntax:Single = Rnd() To produce random numbers in a range, from lowerbound to upperbound… Int((upperbound - lowerbound + 1) * Rnd + lowerbound)

  11. Dim shtLoopCounter, shtX, shtY As Short For shtLoopCounter = 0 To 100 shtX = Int((696 - 0 + 1) * Rnd() + 0) shtY = Int((224 - 0 + 1) * Rnd() + 0) EamonnsPicBox.CreateGraphics.DrawLine(Pens.Blue, 348, 112, shtX, shtY) Next shtLoopCounter Note, this example suffers from “magic numbers”, we will learn to fix this latter

  12. There is a built-in function that will draw (axis parallel) rectangles … EamonnsPicBox.CreateGraphics.DrawRectangle(Pens.Black, 100, 100, 10, 90) EamonnsPicBox.CreateGraphics.DrawRectangle(Pens.Red, 200, 100, 10, 80) EamonnsPicBox.CreateGraphics.DrawRectangle(Pens.Blue, 300, 100, 50, 50) • The parameter list is: • The Pen • The top left corner X’s coordinate • The top left corner Y’s coordinate • The width of the rectangle • The height of the rectangle

  13. It is legal (and sometimes useful) to draw objects that do not fit on the screen (even if this means giving a negative value for a coordinate ) EamonnsPicBox.CreateGraphics.DrawRectangle(Pens.Black, -20, 10, 100, 90)

  14. There is a built-in function that will draw (axis parallel) ellipses… EamonnsPicBox.CreateGraphics.DrawEllipse(Pens.Black, 100, 100, 90, 60) EamonnsPicBox.CreateGraphics.DrawEllipse(Pens.Red, 300, 100, 30, 80) EamonnsPicBox.CreateGraphics.DrawEllipse(Pens.Blue, 500, 100, 50, 50) The parameter list is the same as for drawing rectangles, except we imagine the smallest rectangle that the ellipses we want could fit into…

  15. There is a built-in function that will draw arcs… EamonnsPicBox.CreateGraphics.DrawArc(Pens.Blue, 100, 20, 350, 150, 0, 160) The parameter list is the same as for drawing ellipses, except we also specify the start and sweep of the arc

  16. EamonnsPicBox.CreateGraphics.DrawArc(Pens.Blue, 100, 20, 350, 150, 0, 160) start sweep

  17. There is a built-in function that will draw pie segments… EamonnsPicBox.CreateGraphics.DrawPie(Pens.Blue, 100, 20, 350, 150, 0, 160) The parameter list is the same as for drawing arcs.

  18. The Pen revisited A Pen is an object. We are not going to study objects in VB too much. For now lets think of it like this… We know that a variable, like shtAge has exactly one property, its value, for example 24 or 58. We can think of an object, as having more than one property. What properties do real pens have? They have color, and width We can declare and use a new pen like this.. Dim MyPen As New Pen(Color.Purple, 5) EamonnsPicBox.CreateGraphics.DrawPie(MyPen, 100, 20, 350, 150, 0, 160)

  19. Dim MyPen As New Pen(Color.Purple, 5) EamonnsPicBox.CreateGraphics.DrawPie(MyPen, 100, 20, 350, 150, 0, 160)

  20. Dim MyPen As New Pen(Color.Black, 3) EamonnsPicBox.CreateGraphics.DrawEllipse(MyPen, 100, 100, 90, 60) MyPen.Color = Color.Red MyPen.Width = 15 EamonnsPicBox.CreateGraphics.DrawEllipse(MyPen, 300, 100, 90, 60) Once we have created a pen, we can change its properties and reuse it again and again

  21. The SolidBrush Object I All the functions we have seen thus far have solid versions Dim MyBrush As New SolidBrush(Color.Blue) EamonnsPicBox.CreateGraphics.FillRectangle(MyBrush, 100, 100, 100, 90) EamonnsPicBox.CreateGraphics.FillEllipse(MyBrush, 200, 100, 100, 90) MyBrush.Color = Color.Red EamonnsPicBox.CreateGraphics.FillPie(MyBrush, 300, 20, 350, 150, 0, 160)

  22. The SolidBrush Object II A SolidBrush is an object. What properties do real SolidBrushes have? They have color… We can declare and use a new SolidBrush like this.. Dim MyBrush As New SolidBrush(Color.Blue) EamonnsPicBox.CreateGraphics.FillRectangle(MyBrush, 100, 100, 300, 90)

  23. The Font Object A Font is an object. What properties do real Fonts have? They have typeface and size We can declare and use a new Font like this.. Dim MyFont = New Font("Arial", 46) eamonnsPicBox.CreateGraphics.DrawString("Pan is Dead", MyFont, MyBrush, 100, 100)

  24. Homework/Lab Due on Friday 19th of November (Thursday the 11th is a holiday) at the beginning of class. Use the tools you have learned today (and a few more we will see next time) to create an image of one of the Simpson's characters (I would especially prefer a minor character). You need to first sketch it out on graph paper, and have myself or Eric sign off on it before you proceed. The graph paper drawing should include the locations of some of the major features. Hand in a screen dump, the graph paper, and a printout of the code Do a good job! Because the final project in the class will extend your work here.

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