Can't save current frame as SVG

Processing.py
1

I have tried to find a solution to my issue, but couldn’t. I am using Processing 4 with Python Mode.
I am trying to save the current frame as SVG and exit by pressing the “s” key. However, I am getting the following error:

ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoaders$AppClassLoader and java.net.URLClassLoader are in module java.base of loader 'bootstrap')
	at jycessing.LibraryImporter.addJarToClassLoader(LibraryImporter.java:315)
	at jycessing.LibraryImporter.recursivelyAddJarsToClasspath(LibraryImporter.java:164)
	at jycessing.LibraryImporter.addLibrary(LibraryImporter.java:140)
	at jycessing.LibraryImporter$1.__call__(LibraryImporter.java:82)
	at org.python.core.PyObject.__call__(PyObject.java:480)
	at org.python.core.PyObject.__call__(PyObject.java:484)
	at org.python.pycode._pyx38.f$0(sketch_220501a.pyde:1)
	at org.python.pycode._pyx38.call_function(sketch_220501a.pyde)
	at org.python.core.PyTableCode.call(PyTableCode.java:171)
	at org.python.core.PyCode.call(PyCode.java:18)
	at org.python.core.Py.runCode(Py.java:1614)
	at org.python.core.Py.exec(Py.java:1658)
	at org.python.pycode._pyx37.f$0(C:/Users/user/AppData/Local/Temp/sketch_220501a16544851592084895088/sketch_220501a.pyde:96)
	at org.python.pycode._pyx37.call_function(C:/Users/user/AppData/Local/Temp/sketch_220501a16544851592084895088/sketch_220501a.pyde)
	at org.python.core.PyTableCode.call(PyTableCode.java:171)
	at org.python.core.PyCode.call(PyCode.java:18)
	at org.python.core.Py.runCode(Py.java:1614)
	at org.python.core.Py.exec(Py.java:1658)
	at org.python.util.PythonInterpreter.exec(PythonInterpreter.java:276)
	at jycessing.PAppletJythonDriver.processSketch(PAppletJythonDriver.java:233)
	at jycessing.PAppletJythonDriver.findSketchMethods(PAppletJythonDriver.java:613)
	at jycessing.Runner.runSketchBlocking(Runner.java:399)
	at jycessing.mode.run.SketchRunner.lambda$2(SketchRunner.java:112)
	at java.base/java.lang.Thread.run(Thread.java:833)

Here is my full code:

add_library("svg")
save_frame = False
total_degrees = 360
radius = 0
center_x = 0
center_y = 0
frames = 0

def setup():
    global radius, center_x, center_y, svg_output
    size(1600, 1000)
    background(255)
    stroke(0)
    strokeWeight(1)
    noFill()
    svg_output = createGraphics(width, height, SVG, "file_01.svg")
    radius = height * 0.6
    center_x = width * 0.25
    center_y = height / 2

def draw():    
    global total_degrees, radius, center_x, center_y, frames
    if save_frame:
        beginRecord(svg_output)
        
    translate(frames * 3, 0)
    beginShape()
    for i in range(total_degrees):
        noiseFactor = noise(i * 0.0130, float(frameCount) * 0.0115)
        x = center_x + radius * cos(radians(i)) * noiseFactor
        y = center_y + radius * sin(radians(i)) * noiseFactor
        curveVertex(x, y)
    endShape(CLOSE)

    frames += 1
    radius -= 2
    if radius < 20:
        noLoop()
        
    if save_frame:
        endRecord()
        exit()
 
def keyPressed():
    global save_frame
    if key == "s":
        save_frame = True

I found this solution on the forum and tried to implement, but can’t debug the issue. Any advice is appreciated!

Edit: deleted parts of the code that were not relevant to the issue

2

Perhaps try Processing 3.5.4 instead. Processing 4 is still in beta, so there are issues. I tested the following code in Processing 3.5.4, and I can confirm it works fine –

add_library('svg')
save_frame = False

def setup():
    size(400, 400)

def draw():
    if save_frame:
        beginRecord(SVG, 'file_01.svg')
    square(200, 200, 100)
    if save_frame:
        endRecord()
        exit()
    
def keyPressed():
    global save_frame
    if key == 's':
        save_frame = True
3

Hi there,
Thanks for the prompt reply, I have now gone back to 3.5.4 until version 4 gets more reliable.

Your example seems to work, but the issue is that it only exports the current frame. For example, if I have a loop of translated circles, the “save_frame” wouldn’t export the view with all 300 of them, but only the 300th circle itself. How can I capture everything that has been drawn on my screen up until that moment?

Screenshot_1
Screenshot_11129×979 447 KB

4

It sounds like you don’t actually need the keyPressed() part? Like, you already know how many frames you’d like? So maybe change out the approach for something that employs a loop, which also means you don’t have to wait for the draw() to run 300 times –

add_library('svg')

def setup():
    size(400, 400, SVG, 'output.svg')
    noFill()

def draw():    
    for i in range(300):
        circle(random(width), random(height), 30) 
    exit()

No display window appears, but you’ll see the SVG file pop-out next to your sketch file.

5

This didn’t work for me either. I need to keep the option to stop the draw() at any point when I am satisfied with the result. Therefore a keypressed() is preferred option. It’s just that I can’t seem to find a way to export the full sketch and not only the last frame. Any ideas how to do that and keep the keyPressed() setup?

6

Here’s a hacky solution –

Maybe you use two sketches? One sketch to grab the noise-seed and frame-count values. Then another sketch that renders, which employs a loop and exits after a single draw() (like the example I suggested above).

Sketch 1 looks something like this –

r = int(random(10000))
print('noise seed: ' + str(r))
noiseSeed(r)

def setup():
    size(400, 400)
    noFill()

def draw():
    nx = noise(1, frameCount) * width
    ny = noise(2, frameCount) * height
    circle(nx, ny, 30)

def keyPressed():
    print('stop frame: ' + str(frameCount))
    noLoop()

Let’s say you stop on frame 75 with a noise-seed of 1316. You insert those values into a second sketch (to render the SVG) that looks like this –

add_library('svg')
noiseSeed(1316)  # noise seed value
stop_frame = 75  # stop frame value

def setup():
    size(400, 400, SVG, 'output.svg')
    noFill()

def draw():    
    for i in range(stop_frame):
        nx = noise(1, i) * width
        ny = noise(2, i) * height
        circle(nx, ny, 30)
    exit()

You might combine these two sketches into a single program, somehow. But this two-step process should work fine.