|
| conrgn |
Labels 4-connected components in a binary PGM image.
Use as:
conrgn [g|c] inputfile
If "-" (a single hyphen) is given as inputfile, input is read
from stdin. The output image (on stdout) will be black where the
input image is black. Each nonblack pixel in the input image will be
given a new grayscale output value that labels its connected
component. If the image has fewer than 256 connected components, the
program will output a grayscale PGM image, with each gray level
(except 0) representing a component. If there are more than 255
connected components, the program will output a color PPM image, with
each unique color representing a component. Giving a "g" or
"c" argument before the input filename forces the output to be
either grayscale or color. Forcing grayscale output when there are
more than 255 regions will cause some labels to be reused.
Example: conrgn c blocks_thresh.pgm > blocks_reg.ppm
|
|
| autocolor |
Recolors a grayscale PGM image to make a color PPM image.
Use as:
autocolor inputfile
If "-" (a single hyphen) is given as inputfile, input is read
from stdin. This program takes a grayscale image as input and
produces on stdout a color PPM image of the same size as output. Each
unique gray level in the input (except black) is mapped into a unique
color. Black pixels are left alone. This program is most useful for
viewing the output of conrgn.
Example: autocolor blocks_reg.pgm > blocks_reg.ppm
|
|
| makeelement |
Creates various simple binary PGM images.
Use as:
makeelement box width height
makeelement disk diameter
makeelement ring diameter
This produces (on stdout) various simple binary PGMs of various
shapes. You may find these useful as structuring elements for binary
morphology operations (which you'll have to code for assignment 1).
Example: makeelement disk 9 > disk9.pgm
|
Edge detection |
|
| canedg |
Produces an edge pixel list from a grayscale image.
| Required parameters:
| | -i input | | PGM or PPM format image
| | -o output | | edge pixel description file
| | Optional parameters:
| | -s float | | sigma value for convolution (default 0.4)
| | -m int | | size of convolution mask (default sigma*4)
| | -lt float | | low threshold value (default 1.4)
| | -ht float | | high threshold value (default 2.0)
| | -sp | | print sub-pixel localized values (default false)
|
The subroutine only looks at those pixels which gradients are
greater than the low threshold. If the gradient is greater than the high
threshold, then the pixel is placed into a linked list for later processing
(join edges). So the low threshold is used to reduce the processing time
while high threshold controls the number of edges possibly extracted.
Example: canedg -i blocks.pgm -o block_edgelist.txt
|
|
| edge_filter |
Converts an edge pixel list into a binary image.
| Required parameters:
| | -i input | | edge pixel description file
| | -o output | | PGM format binary image
| | -r int | | number of rows in output image
| | -c int | | number of columns in output image
| | Optional parameters:
| | -l int | | minimum length of edges (default 5)
|
Example: edge_filter -i block_edgelist.txt -o block_edges.pgm -r 256 -c 256
|
|
| canny |
Produces an edge image in PGM format where graylevel 0 represents
edge pixels and graylevel 255 represents background. Note that there
is no default setting for the parameters and also the name of the
output file is determined automatically (see the example below).
| Required parameters:
| | image | | An image to process. Must be in
PGM format.
| | sigma | | Standard deviation of the gaussian
smoothing filter.
| | tlow | | Specifies the low value
to use in hysteresis. This is a fraction (0.0-1.0) of the computed high
threshold edge strength value.
| | thigh | | Specifies the high value
to use in hysteresis. This fraction (0.0-1.0) specifies the percentage
point in a histogram of the gradient of the magnitude. Magnitude values
of zero are not counted in the histogram.
| | Optional parameters:
| | writedirim | | Optional argument to output
a floating point direction image.
|
Implements the following Canny edge detector steps:
1) Convolve the image with a separable gaussian filter.
2) Take the dx and dy the first derivatives using [-1,0,1] and [1,0,-1]'.
3) Compute the magnitude: sqrt(dx*dx+dy*dy).
4) Perform non-maximal suppression.
5) Perform hysteresis.
Also optionally outputs a floating point RAW headerless file of
the edge gradient "up the edge" where the angle is
defined in radians counterclockwise from the x direction.
Example: canny blocks.pgm 0.60 0.50 0.90
|
Object Recognition Toolkit |
|
| chainpix |
Produces a chained pixel list from a PGM binary image.
Takes input from stdin and writes output to stdout. See the output format here.
Example: chainpix < blocks.canny.pgm > blocks.cpx
|
|
| fex |
Segments chained pixel lists produced by chainpix into
straight-line segments and circular arcs.
Takes input from stdin and writes output to stdout. See the output format here.
Example: fex < blocks.cpx > blocks.fex
|
|
| lpeg |
Low-level straight-line grouping. Groups straight-line segments
produced by fex into parallel line pairs and various kinds of line
junctions.
Takes input from stdin and writes output to stdout. See the output format here.
| Optional parameters:
| | -r int | | minimum line length
| | -t int | | max angle between two "parallel" lines
| | -q float | | minimum acceptable quality level
|
Example: lpeg < blocks.fex > blocks.lpg
|
|
| ipeg |
Intermediate-level grouping. Groups the sets produced by lpeg
into triplets, corners, and polygons.
Takes input from stdin and writes output to stdout. See the output format here.
| Optional parameters:
| | -t | | triplets only
| | -c | | corners only
| | -p | | closed polygons only
|
Example: ipeg < blocks.lpg > blocks.ipg
|
|
| ort2image |
Takes the output of fex, lpeg, or ipeg, and draws the
straight-line and circular arc segments, producing a PGM image.
Takes input from stdin and writes output to stdout.
| Optional parameters:
| | -r int | | # of rows
| | -c int | | # of columns
| | -b int | | background intensity
| | -l int int int | | intensity, line thickness, endpoint intensity (for lines?)
| | -i int int int | | intensity, line thickness, endpoint intensity (for curves?)
| | -m int | | minimum length
| | -L | | line segments only
| | -C | | curved segments only
|
Example: ort2image < blocks.ipg > blocks_drawn.pgm
|
(May 17) imgformat.c is updated
again to fix a bug found by Ying Luo. The problem occured in read_ppm_file
while reading the image header for some images.