SYNOPSIS

pfsview [--window_min <log_lum>] [--window_max <log_lum>]

DESCRIPTION

pfsview is a QT application for viewing high-dynamic range images. It expects pfs stream on the standard input and displays the frames in that stream one by one.

pfsv script can be more convienent to use if hdr images are to be displayed without any prior processing.

DYNAMIC RANGE WINDOW

To show high-dynamic range data on a low-dynamic range monitor, pfsview uses concept of a dynamic range window. The dynamic range window is the highest and lowest value that should be mapped to black and white pixel. Values above or below the window are clipped (see clipping methods below). The dynamic range window is displayed in pfsview as a blue area on the dynamic range scale (second toolbox from the top). The window can be moved, shrunk and expended using a mouse or a keyboard.

CLIPPING METHODS

Currently, two clipping methods are available (see View menu):

Simple clipping

The values above and below the dynamic range window are displayed as black or white.

Color-coded clipping

The values above the dynamic range window are displayed as yellow and below the window as green. This is helpful to see which parts of the image do not fit into the selected dynamic range.

Keep brightness and hue

This method tries to preserve brightness and hue while sacrificing color saturation when the colors exceed the RGB color gamut. Colors are desaturated in the RGB color space towards the neutral color (D65) of the corresponding luminance.

MAPPING METHODS

High-dynamic range data are usually better visualized using non-linear scale, for example a logarithmic or a power function. pfsview offers several such scales, shown in View menu. Gray-scale values for each mapping method are computed by the formulas:

LINEAR: y = (x-min)/(max-min)

GAMMA: y = [ (x-min)/(max-min) ]^gamma

LOGARITHMIC: y = (log10(x)-log10(min))/(log10(max)-log10(min))

where y is the gray-scale value after mapping, x is an input HDR value, min and max are lower and upper bounds of the dynamic range window.

REPRODUCING MAPPING WITH PFSGAMMA

To reproduce the displayed image and save it to LDR image using pfs commands, you can use the following commands:

pfsin image.hdr | pfsgamma -g 2.2 -m 0.01 | pfsout image.png

where "2.2" is the gamma value from the "Mapping" combo box, and 0.01 is the exposure value. The exposure is shown as the right-most number in the window status bar of pfsview.

OPTIONS

--window_min <log_lum>

Lower bound of the values that should be displayed or minimum value of the dynamic range window. The value should be given in log_10 units, for example -1 if the lower bound should be 0.1 (10^-1).

--window_max <log_lum>

Upper bound of the values that should be displayed or minimum value of the dynamic range window. The value should be given in log_10 units, for example -1 if the upper bound should be 0.1 (10^-1).

EXAMPLES

pfsin memorial.hdr | pfsview

See the memorial image.

pfsv memorial.hdr

The same as above, but using the utility script 'pv'.