Graphics in HiC

C++ Notes: Graphics in HiC

Computer Graphics

Goal: draw rectangles, circles, other shapes
Basic graphic element: pixel - smallest dot that can be drawn
Graphics output window:
- This window was created by running graphics_101.cpp
- Enabling graphics
  - include library for graphics:
```
        #include <graphics.h>
```
  - Setting things up at runtime; call
```
        SetupGraphics();
```
  - call just once at start of program, typically at start of main
coordinates of upper left corner: (0,0)
y coordinates increase as go down: (0, 350) is the lower left corner (unless the window gets resized)
width: 500 pixels [[what is lower right corner?]]

Drawing a line: move to where line starts, draw line to where it ends

moving to start: MoveTo(X, Y);
line to next point: LineTo(X, Y);

Line from lower left to upper right:

        MoveTo(0, 350);
        LineTo(500, 0);

Triangle:

        MoveTo(200, 100); // top corner
        LineTo(250, 150); // go down right side
        LineTo(150, 150); // across the bottom
        LineTo(200, 100); // back to top corner

A couple of predefined shapes:
- rectangle: Rectangle(X1, Y1, X2, Y2);
```
        Rectangle(200, 200, 250, 250); // gives a square!
```
- circle: Circle(X, Y, radius);
```
        Circle(450, 250, 75);
```
  - note circle extends off edge of drawing; can resize to see rest

Adding Color

Color represented in the computer as red, green, and blue components
- typically: 0-255 on each one for a total of 256 * 256 * 256 = 16,777,216 colors
- a number of common colors have names; use these: Red, Blue, Green, Yellow, Brown, Black, White, Purple, Teal, etc.
  - see HiC help for list of colors: Help|View Library Source|winbase.h

Two items controlling color used: pen and brush

Pen: color of lines drawn:

        SetPenColor(Green);
        // rectangle from (20, 20) to (150, 50) with rounded corners
        //   rounding is controlled by the 10, 5
        RoundRect(20, 20, 150, 50, 10, 5);

Brush: color used to fill in

have both style and color; just setting color has no effect:

        SetBrushColor(Red);
        Circle(400, 50, 35);

default style: Clear; change to Solid to see the paint:

        SetBrushColor(Red);
        SetBrushStyle(Solid);
        Circle(400, 50, 35);

If want shapes with no outlines, set the pen style to ClearPen:

        SetPenStyle(ClearPen);
        SetBrushColor(Orange);
        SetBrushStyle(Cross); // cross-hatch pattern
        Circle(375, 150, 40);

More information:
- graphics_101.cpp: a program illustrating the basics boxes.cpp: nested, colored boxes
- Help|View Library Headers|graphics.h: all operations
  - note this is the library headers, not the library source - see the library source if you want to see the implementations as well
- Help|View Library Source|winbase.h: list of colors (see the bottom of the file)
  - actually, the whole graphics system is object-oriented, so if you dig into winbase.h you'll find you can have multiple graphics windows

Review

#include <graphics.h>
SetupGraphics();
upper left corner: (0, 0); lower right: (500, 350)
MoveTo, LineTo
Rectangle, Circle, RoundRect - many others available
Pen, Brush: control colors/style of drawing