问题
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().
In the Python mode, what to do is not so clear and doesn't seem to be explained by the documentation. You can't declare variables in Python and variables are not automatically global, i.e. if I just say in setup() c = createGraphics(400,400)
and then in draw() say c.beginDraw()
I get a NameError: global name 'c' is not defined
and this can't simply be fixed by saying global c
in the line above.
So how is it done?
回答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()
来源:https://stackoverflow.com/questions/61139974/using-processing-pgraphics-in-python-mode