FBGRID(1)

NAME

fbgrid - draw a calibration grid on a frame buffer

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SYNOPSIS
DESCRIPTION
OPTIONS
EXAMPLES
SEE ALSO
AUTHOR
COPYRIGHT
BUG REPORTS

SYNOPSIS

fbgrid [-c] [-b | -d | -o] [-F framebuffer] [-s squaresize] [-w width] [-n height]

fbgrid draws a calibration grid pattern on a frame buffer. Three intensity levels of grid lines are drawn at different spacings, making it easy to count pixels and verify display geometry. The dark lines are drawn at intensity 64, the grey lines at 128, and the white lines at 255.

The default grid is decimal (-d): dark lines every 10 pixels, grey lines every 50 pixels, and white lines every 100 pixels.

The frame buffer is selected with -F or, if that option is absent, by the FB_FILE environment variable; otherwise the system default device is used (see brlcad(1)).

OPTIONS

-c: Clear the frame buffer to black before drawing the grid.
-b: Use binary spacing: dark lines every 8 pixels, grey lines every 64 pixels, and white lines every 128 pixels.
-d: Use decimal spacing (the default): dark lines every 10 pixels, grey lines every 50 pixels, and white lines every 100 pixels.
-o: Draw the old-style grid: a dotted background with white diagonals from corner to corner and red lines through the center.
-F framebuffer: Specify the frame buffer device to draw on.
-s squaresize: Set both the width and height of the frame buffer to squaresize pixels. -S is an equivalent synonym.
-w width: Set the frame buffer width to width pixels. -W is an equivalent synonym.
-n height: Set the frame buffer height to height scanlines. -N is an equivalent synonym.
-h, -?: Print usage information and exit.

EXAMPLES

Example 1. Verify the geometry of a rendered image

pix-fb -F /tmp/fb moss.pix
fbgrid -F /tmp/fb -d

Display a rendered image on a memory frame buffer and overlay a decimal grid. The grid lines at every 10, 50, and 100 pixels make it easy to measure feature positions and sizes directly off the screen.

Example 2. Calibrate a 1024x1024 display with a binary grid

fbgrid -c -b -s 1024

Clear the frame buffer and draw a binary grid (lines every 8, 64, and 128 pixels) sized to 1024x1024, useful for checking power-of-two display alignment and pixel addressing.