TFT - Arduino Sketches: Tools and Techniques for Programming Wizardry - page 232

The xPos and yPos parameters are int values and specify the center of the
circle. The radius parameter, also an int , is the radius of the circle to print, in
pixels.
Coloring
All the graphical functions take coordinates and parameters to dei ne their size
and shape but do not take parameters for color. This is done through different
functions. The philosophy is this: you tell the controller what color you want
to use, and all subsequent drawing will use that color.
Color functions aren't used only for lines but also for any i lled spaces. A rect-
angle can have one color for the lines dei ning its boundary, while the interior
of the rectangle could be a different color. By specifying a i ll color, anything
present inside the rectangle would be erased by a solid color. The color can be
any RGB value. It's also possible to declare no color, in which case the color is
“transparent”; where any existing pixels are left untouched.
This is accomplished using two functions: stroke() and fill(). To dei ne
the color of points and lines, use stroke() :
screen.stroke(red, green, blue);
This function takes three int values; 8-bit values for the red, green, and blue
components. Again, these values are scaled down to what the TFT screen is
capable of displaying. When this function is called, no previous drawings are
modii ed; only future calls to drawing elements will be affected. This function
works only on points, lines, and outline graphics for circles and rectangles. To
specify how to i ll a circle or rectangle, use fill() :
screen.fill(red, green, blue);
Again, it takes three int values: the red, green, and blue components expressed
as 8-bit values.
To set the outline color as transparent, use the noStroke() function:
screen.noStroke();
To set the i ll color as transparent, use the noFill() function:
screen.noFill();
Graphic Images
If you were creating a weather station with graphic icons on an LCD screen,
it would be possible to create a basic geometric image representing the Sun.
Lightning would be a little more difi cult to render and clouds are quite com-
plicated. It is much easier to use a ready-made image i le to load and display
on the screen. The TFT library can do this off of an SD card.