X - axis left:0 right:width
Y - axis top:0 bottom:height

point(X,Y);

line(X1,Y1,X2,Y2);

ellipseMode(CENTER);
ellipse(CENTERx,CENTERy,WIDTH,HEIGHT);
ellipseMode(CORNER);default!!!
ellipse(TOP,LEFT,WIDTH,HEIGHT);default!!!
ellipseMode(CORNERS);
ellipse(TOP,LEFT,RIGHT,BOTTOM)

rectMode(CENTER);
rect(CENTERx,CENTERy,WIDTH,HEIGHT);
rectMode(CORNER);default!!!
rect(TOP,LEFT,WIDTH,HEIGHT);default!!!
rectMode(CORNERS);
rect(TOP,LEFT,RIGHT,BOTTOM)

0－255代表256种switch
8bit - gray mode
24bit - color mode
红绿蓝alpha各8bit

default:
stroke(0);
fill(255);

hide:
nostroke();
nofill();

前包含后，后包含于前

Exercise 1-4: Try to guess what the instructions would be for the following screenshot.

stroke(0);
  fill(255);
    rect(width/2-1,0,(width-1)/2,(height-1)/2);
  fill(10);
    rect(0,0,(width-1)/2,(height-1)/2);
  fill(100);
    rect(width/2-1,height/2-1,(width-1)/2,(height-1)/2);
  fill(255);
    rect(0,height/2-1,(width-1)/2,(height-1)/2);

Exercise 1-5: Complete the following program. Guess what RGB values to use (you will be

able to check your results in Processing after reading the next chapter). You could also use the

color selector