Issue solved! Unfortunately, it appears that options.interpolate in PsychoJS ImageStim doesn’t function as expected (images are always interpolates linearly, regardless of setting options.interpolate to true or false). However, I found a workaround which serves my purposes - since the rendering of ImageStim is based on PixiJs, I directly edited the PixiJs interpolation setting by inserting
PIXI.settings.SCALE_MODE = PIXI.SCALE_MODES.NEAREST;
via the code component.
Note that this workaround works great for me since I want all my stimuli to not be linearly interpolated. It wouldn’t work if you wanted to simultaneously present one image with applied linear interpolation, the other without. To go back to linear interpolation, inserting
PIXI.settings.SCALE_MODE = PIXI.SCALE_MODES.LINEAR;
in the code component does the trick!