>Psychtoolbox>PsychDemos

HDRDebugViewer([imfilepattern][, scalefactor=autoselect][gpudebug=1]) – Load and show high
dynamic range images on a compatible HDR display setup.

See “help PsychHDR” for system requirements and setup instructions for HDR
display. See “help HDRRead” for supported HDR image file formats, ie. the
formats that HDRRead() can load.

The viewer allows to cycle through a sequence of images in the given
folder, matching the given filename pattern. It allows to adjust the
intensity online, as well as to zoom into regions of the image. A simple
“color picker” displays the RGB color values in units of nits under the cursor
position.

‘imfilepattern’ - Filename search pattern of the HDR images to load,
e.g., ‘myimages*.hdr’ would load all images in the current folder that
are starting with ‘myimages’ and ending with extension ‘.hdr’.

If ‘imfilepattern’ is omitted or empty then image files bundled with
Psychtoolbox and Matlab are loaded. Additionally the viewer will offer to
download some freely useable sample files from the MPI for Informatics in
Saarbruecken, Germany. Another bunch of OpenEXR sample images can be found
on the OpenEXR website under:

https://www.openexr.com/downloads.html

Limitations:

The viewers formulas for converting pixel color values from the units in the
image file to the required linear unit in Nits are not neccessarily correct, as
there seems to be not much agreement about what the units in the image files are
supposed to reflect. In case of Radiance files (.hdr) we multiply by some fixed
number, when we should actually convert from units of Radiance to units of
Luminance. For the OpenEXR format and others, we just use values as they are,
assuming they are already in Nits. This seems to be the case for some, but not all,
sample images.

Similarly the formula for computing frame average light level and max content
light level may or may not be 100% according to spec. At least they give reasonable
results…

Control keys:

You can cycle through all images by pressing the space-bar. You can change
image intensity scaling by pressing the cursor up- and down-keys. You can
exit the viewer by pressing ESCape. By pressing the ‘q’ key, you can
toggle between float precision HDR and 256 level 8 bit quantized output.

Zoom mode:

Pressing the left mouse button will enable zoom mode. Dragging the mouse
while the button is depressed allows to change the region which should be
zoomed. Releasing the mouse button will show the selected region zoomed
up to fullscreen. A single mouse click will reset to the full image.

This is an extension of SimpleHDRDemo.m, see that file for the most basic usage
of HDR displays with Psychtoolbox.