Using Processing PGraphics in Python Mode?

Question

In Processing\'s Java Mode, you use PGraphics objects by declaring them globally, setting them up with createGraphics() in setup() and then referring to them in draw().

Answer 1

It can be fixed using global. Be sure to use global where you initialise the canvas too, otherwise it's a local variable and your global canvas reference may still be None

Here's a basic example:

# global reference
canvas = None

def setup():
    size(300, 300)
    # setup global canvas
    global canvas
    canvas = createGraphics(300, 300)

    canvas.beginDraw()
    canvas.background(0);
    canvas.noStroke()
    canvas.blendMode(DIFFERENCE)
    canvas.ellipse(150,150,150,150)
    canvas.endDraw()

def draw():
    # reference global canvas to draw
    global canvas
    image(canvas,0,0)

def mouseDragged():
    diameter = dist(mouseX,mouseY,pmouseX,pmouseY)
    # reference global canvas to update graphics
    global canvas
    canvas.beginDraw()
    canvas.ellipse(mouseX,mouseY,diameter,diameter)
    canvas.endDraw()