psychopy polygon on top of image

Question

using psychopy ver 1.81.03 on a mac I want to draw a polygon (e.g. a triangle) on top of an image. So far, my image stays always on top and thus hides the polygon, no matter the order I put them in. This also stays true if I have the polygon start a frame later than the image.

e.g. see inn the code below (created with the Builder before compiling) how both a blue square and a red triangle are supposed to start at frame 0, but when you run it the blue square always covers the red triangle!?

Is there a way to have the polygon on top? Do I somehow need to merge the image and polygon before drawing them?

Thank you so much for your help!!

Sebastian

#!/usr/bin/env python2
# -*- coding: utf-8 -*-
"""
This experiment was created using PsychoPy2 Experiment Builder (v1.81.03), Sun Jan 18 20:44:26 2015
If you publish work using this script please cite the relevant PsychoPy publications
  Peirce, JW (2007) PsychoPy - Psychophysics software in Python. Journal of Neuroscience Methods, 162(1-2), 8-13.
  Peirce, JW (2009) Generating stimuli for neuroscience using PsychoPy. Frontiers in Neuroinformatics, 2:10. doi: 10.3389/neuro.11.010.2008
"""

from __future__ import division  # so that 1/3=0.333 instead of 1/3=0
from psychopy import visual, core, data, event, logging, sound, gui
from psychopy.constants import *  # things like STARTED, FINISHED
import numpy as np  # whole numpy lib is available, prepend 'np.'
from numpy import sin, cos, tan, log, log10, pi, average, sqrt, std, deg2rad, rad2deg, linspace, asarray
from numpy.random import random, randint, normal, shuffle
import os  # handy system and path functions

# Ensure that relative paths start from the same directory as this script
_thisDir = os.path.dirname(os.path.abspath(__file__))
os.chdir(_thisDir)

# Store info about the experiment session
expName = u'test_triangle_over_square'  # from the Builder filename that created this script
expInfo = {'participant':'', 'session':'001'}
dlg = gui.DlgFromDict(dictionary=expInfo, title=expName)
if dlg.OK == False: core.quit()  # user pressed cancel
expInfo['date'] = data.getDateStr()  # add a simple timestamp
expInfo['expName'] = expName

# Data file name stem = absolute path + name; later add .psyexp, .csv, .log, etc
filename = _thisDir + os.sep + 'data/%s_%s_%s' %(expInfo['participant'], expName, expInfo['date'])

# An ExperimentHandler isn't essential but helps with data saving
thisExp = data.ExperimentHandler(name=expName, version='',
    extraInfo=expInfo, runtimeInfo=None,
    originPath=None,
    savePickle=True, saveWideText=True,
    dataFileName=filename)
#save a log file for detail verbose info
logFile = logging.LogFile(filename+'.log', level=logging.EXP)
logging.console.setLevel(logging.WARNING)  # this outputs to the screen, not a file

endExpNow = False  # flag for 'escape' or other condition => quit the exp

# Start Code - component code to be run before the window creation

# Setup the Window
win = visual.Window(size=(1280, 800), fullscr=True, screen=0, allowGUI=False, allowStencil=False,
    monitor='testMonitor', color=[0,0,0], colorSpace='rgb',
    blendMode='avg', useFBO=True,
    )
# store frame rate of monitor if we can measure it successfully
expInfo['frameRate']=win.getActualFrameRate()
if expInfo['frameRate']!=None:
    frameDur = 1.0/round(expInfo['frameRate'])
else:
    frameDur = 1.0/60.0 # couldn't get a reliable measure so guess

# Initialize components for Routine "trial"
trialClock = core.Clock()
ISI = core.StaticPeriod(win=win, screenHz=expInfo['frameRate'], name='ISI')
square = visual.ImageStim(win=win, name='square',units='pix', 
    image=None, mask=None,
    ori=0, pos=[0, 0], size=[200, 200],
    color=u'blue', colorSpace='rgb', opacity=1,
    flipHoriz=False, flipVert=False,
    texRes=128, interpolate=True, depth=-1.0)
polygon = visual.ShapeStim(win=win, name='polygon',units='pix', 
    vertices = [[-[200, 300][0]/2.0,-[200, 300][1]/2.0], [+[200, 300][0]/2.0,-[200, 300][1]/2.0], [0,[200, 300][1]/2.0]],
    ori=0, pos=[0, 0],
    lineWidth=1, lineColor=[1,1,1], lineColorSpace='rgb',
    fillColor=u'red', fillColorSpace='rgb',
    opacity=1,interpolate=True)

# Create some handy timers
globalClock = core.Clock()  # to track the time since experiment started
routineTimer = core.CountdownTimer()  # to track time remaining of each (non-slip) routine 

#------Prepare to start Routine "trial"-------
t = 0
trialClock.reset()  # clock 
frameN = -1
# update component parameters for each repeat
# keep track of which components have finished
trialComponents = []
trialComponents.append(ISI)
trialComponents.append(square)
trialComponents.append(polygon)
for thisComponent in trialComponents:
    if hasattr(thisComponent, 'status'):
        thisComponent.status = NOT_STARTED

#-------Start Routine "trial"-------
continueRoutine = True
while continueRoutine:
    # get current time
    t = trialClock.getTime()
    frameN = frameN + 1  # number of completed frames (so 0 is the first frame)
    # update/draw components on each frame

    # *square* updates
    if frameN >= 0 and square.status == NOT_STARTED:
        # keep track of start time/frame for later
        square.tStart = t  # underestimates by a little under one frame
        square.frameNStart = frameN  # exact frame index
        square.setAutoDraw(True)

    # *polygon* updates
    if frameN >= 0 and polygon.status == NOT_STARTED:
        # keep track of start time/frame for later
        polygon.tStart = t  # underestimates by a little under one frame
        polygon.frameNStart = frameN  # exact frame index
        polygon.setAutoDraw(True)
    # *ISI* period
    if t >= 0.0 and ISI.status == NOT_STARTED:
        # keep track of start time/frame for later
        ISI.tStart = t  # underestimates by a little under one frame
        ISI.frameNStart = frameN  # exact frame index
        ISI.start(0.5)
    elif ISI.status == STARTED: #one frame should pass before updating params and completing
        ISI.complete() #finish the static period

    # check if all components have finished
    if not continueRoutine:  # a component has requested a forced-end of Routine
        routineTimer.reset()  # if we abort early the non-slip timer needs reset
        break
    continueRoutine = False  # will revert to True if at least one component still running
    for thisComponent in trialComponents:
        if hasattr(thisComponent, "status") and thisComponent.status != FINISHED:
            continueRoutine = True
            break  # at least one component has not yet finished

    # check for quit (the Esc key)
    if endExpNow or event.getKeys(keyList=["escape"]):
        core.quit()

    # refresh the screen
    if continueRoutine:  # don't flip if this routine is over or we'll get a blank screen
        win.flip()
    else:  # this Routine was not non-slip safe so reset non-slip timer
        routineTimer.reset()

#-------Ending Routine "trial"-------
for thisComponent in trialComponents:
    if hasattr(thisComponent, "setAutoDraw"):
        thisComponent.setAutoDraw(False)
win.close()
core.quit()

Michael MacAskill · Accepted Answer

As per Jonas' comment above, PsychoPy uses a layering system in which subsequent stimuli are drawn on top of previous stimuli (as in his code examples).

In the graphical Builder environment, drawing order is represented by the vertical order of stimulus components: stimuli at the top are drawn first, and ones lower down are progressively layered upon them.

You can change the order of stimulus components by right-clicking on them and selecting "Move up", "move down", etc as required.

Sebastian, has, however, identified a bug here, in that the intended drawing order is not honoured between ImageStim and ShapeStim components. As a work-around, you might be able to replace your ShapeStim with a bitmap representation, displayed using an ImageStim. Multiple ImageStims should draw correctly (as do multiple ShapeStims). To get it to draw correctly on top of another image, be sure to save it as a .png file, which supports transparency. That way, only the actual shape will be drawn on top, as its background pixels can be set to be transparent and will not mask the the underlying image.

For a long-term solution, I've added your issue as a bug report to the PsychoPy GitHub project here: https://github.com/psychopy/psychopy/issues/795

psychopy polygon on top of image

Answers (2)

Related Questions