Re: [psychopy-users] Does PsychoPy allow image "fade in - fade out" transitions?

[Jeremy Gray]

Hi Steve,

This is certainly possible, by setting the image opacity dynamically. Start it at 0.0 and increase to 1.0 over your rise-time window, hold, then ramp it back down. In the builder you'd need to calculate an opacity value as a function of time (or visual frame) in a code component, and then set the opacity to that value on every frame.

--Jeremy

On Fri, May 10, 2013 at 8:44 PM, Steve H. <stavros.ha...@gmail.com> wrote:

Hello,

I'd like to set up an experiment in which random images will be flickered on the screen for 2 seconds and the participant will have to identify them.

Now, the issue that I try to avoid here is having the image appear immediately, that is, "flashing" on the screen. 

Ideally, I'd like to have the trial start with a black screen, then have the first stimulus appear gradually ("fade in" from black), stay on the screen for 2 seconds and then "fade out" to black.

Is this possible to do with PsychoPy? 

My apologies if I'm too vague here, let me know if you need me to explain this better and thank you in advance.

SH

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[Steve H.]

Thank you for the prompt reply Jeremy. In the builder, I would have to set 3 functions separate by commas in the opacity box?

Greatly appreciated.

Stavros

[Michael MacAskill]

On 11 May, 2013, at 14:35, Steve H. <stavros.ha...@gmail.com> wrote:

> Thank you for the prompt reply Jeremy. In the builder, I would have to set 3 functions separate by commas in the opacity box?

No: in the opacity box just put a single variable name, say, 'alpha' (without the quotes), and select "set every frame".

The value of alpha will be set by code in the "each frame" box of a Code component. e.g. if you want it to fade in and out over 0.5 s and be displayed at full opacity for 2 s in between, here is some untested code:

if t < 0.5:
alpha = t / 0.5 # ramp from 0 at the beginning, 1.0 at the end
elif t > 2.0:
alpha = 1.0 - ((t-2.5) / 0.5) # ramp down from 1 to 0
else:
alpha = 1.0 # must be in the middle 2s period

The Code component should appear above the stimulus in the Builder GUI so that the alpha value is calculated before the stimulus is drawn on each frame.


Cheers,

Michael

[Michael MacAskill]

On 11 May, 2013, at 15:45, Michael MacAskill <michael....@otago.ac.nz> wrote:

> elif t > 2.0:

Oops, that should actually be "t > 2.5" in that particular example.

[Steve H.]

Works like a charm Mike! 

Thank you both for the prompt replies. This has solved the issue and I'll post the code once the experiment has been set up.

Thanks again!

[Jeremy Gray]

In the Builder, in an image's Opacity box, put a new variable name "fader" (but without the quotes), and set it to update every frame. In the Stop (duration) box, put "$img_dur" (no quotes) Then add a new code component to the routine. In the Begin routine box, put 

fader = 0  # starting opacity, 0 = transparent

img_dur = 2  # total display time for the image

fade_over = 0.5  # how long a full fade-in/out should take

f_clock = core.Clock()

And in the Each frame box put this:

f = f_clock()

if f < fade_over:

  fader = f / fade_over

else:

  fader = min(1, (img_dur-f)/fade_over)

This will give you a linear ramp in/out. Other forms are possible, just change the math each frame.

--Jeremy

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[Jeremy Gray]

dop! now I just saw Mike's excellent answer.

[Steve H.]

Hi Jeremy, thanks for the input.

I'm getting the following error when I try to run it:

"f= f_clock()

AttributeError: Clock instance has no __call__ method"

Here's the script (created by Builder):

#!/usr/bin/env python

# -*- coding: utf-8 -*-

"""

This experiment was created using PsychoPy2 Experiment Builder (v1.76.00), May 11, 2013, at 13:32

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, 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

# Store info about the experiment session

expName = u'Blur (alternative code)'  # 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

# Setup files for saving

if not os.path.isdir('data'):

    os.makedirs('data')  # if this fails (e.g. permissions) we will get error

filename = 'data' + os.path.sep + '%s_%s' %(expInfo['participant'], expInfo['date'])

logFile = logging.LogFile(filename+'.log', level=logging.EXP)

logging.console.setLevel(logging.WARNING)  # this outputs to the screen, not a file

# 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)

# Setup the Window

win = visual.Window(size=(1920, 1080), fullscr=True, screen=0, allowGUI=False, allowStencil=False,

    monitor='testMonitor', color=[0,0,0], colorSpace='rgb')

# Initialize components for Routine "trial"

trialClock = core.Clock()

image = visual.ImageStim(win=win, name='image',

    image=u'D:\\Artist Perception\\Artist Perception\\New Stimuli\\Cropped Test Stimuli\\CroppedBat11.bmp', mask=None,

    ori=0, pos=[0, 0], size=[0.5, 0.5],

    color=[1,1,1], colorSpace=u'rgb', opacity=1.0,

    texRes=128, interpolate=False, depth=0.0)

# 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

fader = 0  # starting opacity, 0 = transparent

img_dur = 2  # total display time for the image

fade_over = 0.5  # how long a full fade-in/out should take

f_clock = core.Clock()

# keep track of which components have finished

trialComponents = []

trialComponents.append(image)

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

    

    # *image* updates

    if t >= 0.0 and image.status == NOT_STARTED:

        # keep track of start time/frame for later

        image.tStart = t  # underestimates by a little under one frame

        image.frameNStart = frameN  # exact frame index

        image.setAutoDraw(True)

    elif image.status == STARTED and t >= (0.0 + img_dur):

        image.setAutoDraw(False)

    if image.status == STARTED:  # only update if being drawn

        image.setOpacity(fader, log=False)

    f = f_clock()

    if f < fade_over:

      fader = f / fade_over

    else:

      fader = min(1, (img_dur-f)/fade_over)

    

    # check if all components have finished

    if not continueRoutine:  # a component has requested that we end

        routineTimer.reset()  # this is the new t0 for non-slip Routines

        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 event.getKeys(["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()

#-------Ending Routine "trial"-------

for thisComponent in trialComponents:

    if hasattr(thisComponent, "setAutoDraw"):

        thisComponent.setAutoDraw(False)

win.close()

core.quit()

This is the machine I use for the program:

Win 8 Pro x64

PCPartPicker part list: http://pcpartpicker.com/p/blx1

Price breakdown by merchant: http://pcpartpicker.com/p/blx1/by_merchant/

Benchmarks: http://pcpartpicker.com/p/blx1/benchmarks/

CPU: Intel Core i5-3570K 3.4GHz Quad-Core Processor  ($189.99 @ Microcenter) 

CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler  ($24.99 @ Newegg) 

Motherboard: ASRock Z68 Extreme3 Gen3 ATX  LGA1155 Motherboard 

Memory: G.Skill Ripjaws X Series 16GB (4 x 4GB) DDR3-1866 Memory  ($139.99 @ Newegg) 

Storage: Corsair Force Series GT 120GB 2.5" Solid State Disk  ($129.99 @ Newegg) 

Storage: Seagate Barracuda ES 750GB 3.5" 7200RPM Internal Hard Drive 

Video Card: EVGA GeForce GTX 670 2GB Video Card  ($369.99 @ NCIX US) 

Case: Cooler Master Storm Scout ATX Mid Tower Case  ($54.99 @ Newegg) 

Power Supply: Antec EarthWatts Green 650W 80 PLUS Bronze Certified ATX12V Power Supply  ($77.99 @ Adorama) 

Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer  ($16.99 @ Newegg) 

Total: $1004.92

(Prices include shipping, taxes, and discounts when available.)

(Generated by PCPartPicker 2013-05-11 13:35 EDT-0400)

Best,

Steven

[Jeremy Gray]

Oops typo on my part. Should be:

f=f_clock.getTime()

/* sent from a phone; pls forgive typo & brevity */ 

To view this discussion on the web visit https://groups.google.com/d/msg/psychopy-users/-/QTJWjBGUU5cJ.

[SH]

Thank you, Jeremy- confirmed, works on my end. 

Sorry to be a pest, but would it be possible to both ramp on-maintain-ramp off an image and flicker it at the same time?

Many thanks once again.

SH

[Jonas Lindeløv]

Yes, the flicker part is simply achieved by only drawing stimulus on some of the frames. But if the flicker is going to be fast, you probably want to time the presentation to monitor frames instead of continuous time as it is in Michaels example.

So if you want, say, 3 frames (50 ms on a 60 Hz monitor) stimulus and 3 frames black, you would do something like:

# Initiate stimuli etc.

from __future__ import division

from psychopy import visual

win = visual.Window()

stim = visual.TextStim(win)

# General version

fadeIn = 30  # Duration of fadein in frames

fadeOut = 30  # Duration of fadeout in frames

maintain = 120  # Duration of maintenance in frames

flickerInterval = 3  # Duration of on and off duration (3 --> 6 frames per cycle)

for frame in range(fadeIn + fadeOut + maintain):

    if frame < fadeIn:

        alpha = frame / fadeIn  # ramp up

    if frame > fadeIn + maintain:

        alpha = 1.0 - ((frame - fadeIn - maintain) / fadeOut)  # ramp down

    else:

        alpha = 1.0  # Maintain

    

    # Draw only on certain frames

    if frame / flickerInterval % 2 < 1:

        stim.setOpacity(alpha)

        stim.draw()

    win.flip()

If the variables are confusing, here is the same code with fewer variables:

# .... or version with numbers instead of variables

for frame in range(180):

    if frame < 30:

        alpha = frame / 30  # ramp up

    if frame > 150:

        alpha = 1.0 - ((frame - 150) / 30)  # ramp down

    else:

        alpha = 1.0  # Maintain

    

    # Draw only on certain frames

    if frame / 3 % 2 < 1:

        stim.setOpacity(alpha)

        stim.draw()

    win.flip()

The flicker-line with the % might be a bit confusing. It uses modulus and the output is like this for flickerInterval = 3:

for frame in range(20):

   print frame, frame / flickerInterval % 2 < 1 

0 True

1 True

2 True

3 False

4 False

5 False

6 True

7 True

8 True

9 False

10 False

11 False

12 True

13 True

14 True

15 False

16 False

17 False

18 True

19 True

... meaning "three frames on, then three frames off, then three frames on" etc.

Best,

Jonas

[SH]

Hi Jonas, thank you for your contribution.

I'm testing your code now and I get this error with either 'numbers' or 'variables' versions:

image.setOpacity(alpha, log=False)

NameError = 'alpha' is not defined

I pasted the code exactly as is here.

All the best,

SH

[Michael MacAskill]

On 13 May, 2013, at 05:17, SH <stavros.ha...@gmail.com> wrote:

> Hi Jonas, thank you for your contribution.
>
> I'm testing your code now and I get this error with either 'numbers' or 'variables' versions:
>
> image.setOpacity(alpha, log=False)
> NameError = 'alpha' is not defined
>
> I pasted the code exactly as is here.

Jonas' code is written as an example for the Coder view: it contains the entire drawing loop. It would take some modification to work within a Code component of the Builder (which I think you are using?) as Builder maintains its own drawing loop.

Mike

[SH]

Hello once again. I've been trying to get flicker to work in builder using different types of script based on Jonas's but I can't seem to get it right. The code that I'm attaching here does exactly what I want in terms of stimuli presentation except from lack of flickering. 

I have tried googling flickering in python but haven't found a source of information yet. What would be the best way to start learning on how to add flickering to a script in Builder?

Thank you,

SH

[Andrew Poppe]

Hi SH,

attached are a builder script that produces flickering on my machine and the picture I was using. 

Hope that helps.

Andrew

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[SH]

Hi Andrew,

Thank you, greatly appreciated. I'm working on this right now.

Firstly, this is what the presentation looks like:

Ramp On -> Hold - Ramp Off

just by copying the following lines to enable flickering, this is what happens 

Flicker Ramp On -> Hold (no flickering) -> Flicker Ramp Off

Code:

if (frameN//3) % 2 == 0:

    image.draw()

I'm working on this part now to allow flickering to occur during the whole presentation.

All the best,

SH 

[Jonathan Peirce]

You can set the contrast and/or opacity to any value you like at any time. But psychopy doesn't have built-in methods to control these - you'd have to write your own code to handle custom on/off transitions.

Jon

To view this discussion on the web visit https://groups.google.com/d/msgid/psychopy-users/4004272d-7811-48e7-a7a7-9b2dfefc0e2e%40googlegroups.com?hl=en.

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-- 
Jonathan Peirce
Nottingham Visual Neuroscience

http://www.peirce.org.uk

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[SH]

Hi Jon,

Yes, I've been studying Python on the side ("A byte of Python") so I can write my own code for this. 

So far I had no luck with what I want to do though. It seems the "hold" command for opacity is not allowing to have flickering taking place at the same time.

Will keep at it.

Best,

SH