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Check a stimulus file against stimulus PNGs

Source: R/checkStimulusPNGs2IFC.R
checkStimulusPNGs2IFC.Rd

Compares the noise a stimulus .Rdata file records with the stimulus PNGs in a folder, trial by trial. An original and an inverted stimulus hold the same base image, so their difference is the trial's noise alone: ori - inv equals the noise divided by 0.6 for ordinary interior pixels. Older PNGs can wrap a value above white into the interior; their difference is compared with the corresponding 8-bit byte-wrap offset too. The base images are therefore not needed. A wrapped pixel encoded as an endpoint is excluded.

Usage

checkStimulusPNGs2IFC(rdata, png_dir, label = NULL, seed = NULL)

Arguments

rdata

Path to the .Rdata file to check, as written by generateStimuli2IFC.

png_dir

Directory holding the stimulus PNGs. Required; there is no default.

label, seed

The label and seed the PNGs were generated with, which their names carry. When omitted: the values stored in rdata. Pass the archive's own when rdata is a candidate regenerated with other settings, so the PNGs can be found; seed = NULL for a set generated with seed = NULL.

Value

A data frame with one row per base label and trial: base, trial, share (the share of compared pixels whose ori - inv agrees with the file's noise divided by 0.6, directly or after a feasible historical 8-bit byte wrap, to within 1/255), compared (the number of pixels with both decoded PNG values strictly between 0 and 1) and missing (TRUE when either PNG is absent, with share NA). Its unchecked attribute lists PNGs in png_dir that carry label and seed but belong to no row, such as trials beyond the file's n_trials.

No verdict is returned. In the configurations measured in https://github.com/rdotsch/rcicr/blob/main/analyses/stimulus-png-residuals.md, a wrong nscales, seed, noise type, base order or use_same_parameters agreed on 2.1% to 7.4% of pixels per trial, but a Gabor sigma of 24 where the PNGs used 25 on 95% to 99.6%: compare candidates against the same PNGs. Check every base label, since with several bases a wrong use_same_parameters shows only after the first.

Warns about missing and unchecked PNGs, and stops if no PNG named for label and seed exists.

Details

Use it to confirm that a regenerated .Rdata file matches an archive of stimulus PNGs whose original file was lost; vignette("recipes", package = "rcicr"), "When the .Rdata file is lost", shows how.

See also

vignette("recipes", package = "rcicr"), "When the .Rdata file is lost".

Examples

base_face <- tempfile(fileext = ".png")
png::writePNG(matrix(runif(32 * 32), 32, 32), base_face)
stimulus_path <- tempfile("stimuli")
generateStimuli2IFC(list(face = base_face), n_trials = 3, img_size = 32,
                    stimulus_path = stimulus_path, seed = 1, ncores = 1, nscales = 2)
#> 
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rdata <- list.files(stimulus_path, pattern = "\\.Rdata$", full.names = TRUE)
checkStimulusPNGs2IFC(rdata, stimulus_path)
#>   base trial share compared missing
#> 1 face     1     1     1024   FALSE
#> 2 face     2     1     1024   FALSE
#> 3 face     3     1     1024   FALSE