PNG-FB(1)

NAME

png-fb - display a PNG image file on a framebuffer

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SYNOPSIS
DESCRIPTION
OPTIONS
EXAMPLES
SEE ALSO
AUTHOR
COPYRIGHT
BUG REPORTS

SYNOPSIS

png-fb [-H] [-i] [-c] [-v] [-z] [-1] [-m _#lines_] [-F _framebuffer_] [-g _screen_gamma_] [-S _squarescrsize_] [-W _scr_width_] [-N _scr_height_] [-x _file_xoff_] [-y _file_yoff_] [-X _scr_xoff_] [-Y _scr_yoff_] [_file.png_]

png-fb reads a Portable Network Graphics (PNG) format image from the named file, or from standard input if no file is given, and displays it on the currently selected framebuffer. The environment variable FB_FILE selects the default framebuffer (see brlcad(1)); the -F option overrides it.

If no screen size is requested, the framebuffer is opened to match the size of the input image. Grayscale and palette-based images are expanded to RGB, and 16-bit samples are reduced to 8 bits. The reverse conversion, writing a framebuffer image to a PNG file, is performed by fb-png(1).

OPTIONS

-H: Print a single line on standard output giving the image dimensions in a form usable in shell scripts (e.g. WIDTH=42 HEIGHT=17) and exit without displaying the image.
-i: Invert the image, drawing it upside-down.
-c: Clear the framebuffer to black before displaying. By default the new image is written over whatever is already on the screen.
-v: Be verbose, reporting the color type, bit depth, image size, gamma, interlace status, and any embedded text or modification-time chunks.
-z: Zoom and center the image so it fills the display area, using the framebuffer fb_view() routine. Only integer zoom factors are available, so non-square displays may find this of limited use.
-1: Force the image to be written one scanline at a time with fb_write(3). This is the default and overrides -m.
-m #lines: Write the image in rectangular blocks of #lines scanlines using fb_writerect(3) rather than one line at a time. This can be significantly faster on some framebuffers. Block writes are only used when the image is not inverted or zoomed and is no wider than the screen; otherwise display falls back to single-line writes.
-F framebuffer: Display on the explicitly named framebuffer instead of the one named by FB_FILE.
-g screen_gamma: Additional gamma correction to apply for the display screen (default 1.0, i.e. none). Larger values produce a lighter image.
-S squarescrsize: Set both the framebuffer width and height to squarescrsize pixels.
-W scr_width: Set the framebuffer width, in pixels.
-N scr_height: Set the framebuffer height, in scanlines.
-x file_xoff: Skip file_xoff pixels into the image horizontally before displaying.
-y file_yoff: Skip file_yoff pixels into the image vertically before displaying.
-X scr_xoff: Offset the displayed image scr_xoff pixels horizontally on the screen.
-Y scr_yoff: Offset the displayed image scr_yoff pixels vertically on the screen.

The coordinate system for the offsets is first quadrant, with the origin at the lower left corner of the image.

EXAMPLES

Example 1. Render a model and display the result

rt -o render.png -w 1024 -n 1024 havoc.g havoc
png-fb -c render.png

Ray-traces a geometry database to a 1024x1024 PNG file with rt(1), then clears the framebuffer and displays the rendered image.

Example 2. Probe an image size from a script

eval $(png-fb -H earth.png)
echo "image is ${WIDTH} by ${HEIGHT}"

Uses -H to read back the dimensions of a PNG without displaying it, capturing them as shell variables for further processing.