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function SimpleHDRDemo(imfilename)
% SimpleHDRDemo([imfilename]) - Load and show a high dynamic range (HDR) image
% on a compatible HDR display setup.
%
% Press any key to terminate the demo.
%
% 'imfilename' - Optional filename of the HDR image to load. This will load
% a standard HDR demo image bundled with Matlab, if omitted, or abort if
% the default demo image is missing. Currently only '.hdr' RGBE images are
% supported.
%
% See "help PsychHDR" for system requirements and setup instructions for HDR
% display. Once these are satisfied, converting a standard Psychtoolbox visual
% stimulation script into a HDR script is straightforward, as shown in this simple
% demo. Modify your scripts in the following manner:
%
% 1. Use (as most minimal setup) the sequence ...
%
% PsychImaging('PrepareConfiguration');
% PsychImaging('AddTask', 'General', 'EnableHDR');
% win = PsychImaging('OpenWindow', screenid);
%
% ... instead of ...
%
% win = Screen('OpenWindow', screenid);
%
% ... to open a fullscreen onscreen window on a HDR capable display device,
% which is attached to a HDR capable graphics card.
%
% 2. Use HDRRead(imfilename) instead of imread(imfilename) to load HDR
% image files as double() precision matrices.
%
% 3. Optional: Set the optional 'floatprecision' flag of Screen('MakeTexture', ...)
% to 1 or 2 to enforce creation of floating point precision HDR textures
% of a specific precision from your image matrix.
%
% By default, 'floatprecision' will be selected as 2 for single
% precision float fp32 format, which is the maximum precision for
% processing and displaying HDR images.
%
%
% See the section 'EnableHDR' of "help PsychImaging" for more optional parameters
% to pass to PsychImaging('AddTask', 'General', 'EnableHDR'); for customizing the
% HDR display mode. See "help PsychHDR" for more helper subfunctions to customize
% HDR display further at runtime, once the fullscreen onscreen HDR display window
% has been opened and initially set up by PsychImaging('AddTask', 'General', 'EnableHDR').
%
% History:
%
% 21-Jul-2020 mk Written.
% Make sure we run on Psychtoolbox-3. Abort otherwise. Use unified key names for
% keyboard input across all supported operating systems. Use normalized color range,
% not the old 0-255 8 bit color convention:
PsychDefaultSetup(2);
% imfilename provided?
if nargin < 1 || isempty(imfilename)
% No: Try some default file from our bundled OpenEXR sample images:
imfilename = [PsychtoolboxRoot 'PsychDemos/OpenEXRImages/Desk.exr'];
end
% Does imfilename exist?
if ~exist(imfilename, 'file')
error('Specified HDR image file does not exist under path %s.', imfilename);
end
% Read HDR file, abort on error. Must be in a file format recognized by HDRRead:
[img, info] = HDRRead(imfilename);
% Show metadata:
disp(info);
% Find screen to display on: We choose the one with the highest number,
% assuming this is the HDR display:
screenid = max(Screen('Screens'));
% Set a cleanup function: If the variable 'canary' goes out of scope due to
% script termination (error or user abort), call "sca" which will close the display:
canary = onCleanup(@sca);
% Open a double-buffered fullscreen onscreen window in HDR mode on the HDR
% display, with black background color. Color values will be specified in
% units of nits, the display is done according to HDR10 standard, ie.
% Color space is BT2020, SMPTE ST-2084 PQ encoding is used to drive the
% display, output color signals have 10 bpc precision.
PsychImaging('PrepareConfiguration');
PsychImaging('AddTask', 'General', 'EnableHDR', 'Nits', 'HDR10');
% Note: This would also work, as above settings are used by default:
% PsychImaging('AddTask', 'General', 'EnableHDR');
win = PsychImaging('OpenWindow', screenid, 0);
HideCursor(win);
% Convert img from its source colorspace to the display colorspace of the
% HDR onscreen window. info.ColorGamut is the color gamut parsed from the
% image file, or a default color gamut as mandated by the image file format
% spec for the image file. win is the onscreen window handle, and the
% function will query win for the color gamut of its associated colorspace:
[~, img] = ConvertRGBSourceToRGBTargetColorSpace(info.ColorGamut, win, img);
switch info.format
case 'rgbe'
% HACK: Multiply by 179.0 as a crude approximation of Radiance
% units to nits: This is not strictly correct, but will do to get a
% nice enough picture for demo purpose. See 'help HDRRead' for the
% motivation for the 179 multiplicator for Radiance images:
% This is always RGB, no alpha channel to deal with.
img = img * 179;
case 'openexr'
% Known scaling factor for scaling pixel values into units of nits?
% Otherwise it is best to just leave it as is:
if info.sampleToNits > 0
% Only scale RGB channels, not the alpha channel.
img(:,:,1:3) = img(:,:,1:3) * info.sampleToNits;
end
otherwise
error('Unknown image format. Do not know how to convert into units of Nits.');
end
% Compute maximum and max mean luminance of the image:
[maxFALL, maxCLL] = ComputeHDRStaticMetadataType1ContentLightLevels(img);
% Tell the HDR display about maximum frame average light level and maximum
% content light level of the image:
PsychHDR('HDRMetadata', win, 0, maxFALL, maxCLL);
% Build a 32 bpc single-precision float texture from the image
% array by setting the (optional) 'floatprecision' flag to 2.
% texid = Screen('MakeTexture', win, img, [], [], 2);
%
% Or simply don't, because the 'floatprecision' flag defaults to 2
% in HDR display mode anyway if omitted, for your convenience:
texid = Screen('MakeTexture', win, img);
% Some variable rotation angle for the image, for some simplistic animation:
rotAngle = 0;
% Some framecounter for stats:
framecounter = 0;
% Initial Flip to sync us to retrace:
vbl = Screen('Flip', win);
tstart = vbl;
% Animation loop: Show a rotating HDR image, until key press:
while ~KbCheck
% Draw our HDR texture at specified rotation angle, centered in the window:
Screen('DrawTexture', win, texid, [], [], rotAngle);
% Draw some 2D filled oval, with a bounding box of [left,top,right,bottom]
% = [500 500 600 600], and a color value of [R, G, B] = [300 nits, 300 nits, 0 nits],
% ie. a yellow oval with 300 nits:
Screen('FillOval', win, [300 300 0], [500 500 600 600]);
% And some text, 30 pixels high, centered, in a 200 nits green:
Screen('TextSize', win, 30);
DrawFormattedText(win, 'If it works, it works.\nIf it doesn''t, it doesn''t.\n(Quoc Vuong, 2006)', 'center', 'center', [0 200 0]);
% Show updated HDR framebuffer at next vertical retrace:
vbl = Screen('Flip', win);
% Increase rotation angle to make it a bit more interesting:
rotAngle = rotAngle + 0.1;
% Count our frames:
framecounter = framecounter + 1;
end
% We are done. Release all textures, close all windows, shutdown:
sca;
% Print the stats:
duration = vbl - tstart;
averagefps = framecounter / duration;
fprintf('Displayed %i frames in %f seconds, for an average framerate of %f fps.\n', framecounter, duration, averagefps);
fprintf('Bye bye!\n');
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