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Leptonica 1.85.0
Image processing and image analysis suite
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Leptonica 1.85.0
Image processing and image analysis suite
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#include "allheaders.h"Go to the source code of this file.
Functions | |
| PIX * | pixSobelEdgeFilter (PIX *pixs, l_int32 orientflag) |
| PIX * | pixTwoSidedEdgeFilter (PIX *pixs, l_int32 orientflag) |
| l_ok | pixMeasureEdgeSmoothness (PIX *pixs, l_int32 side, l_int32 minjump, l_int32 minreversal, l_float32 *pjpl, l_float32 *pjspl, l_float32 *prpl, const char *debugfile) |
| NUMA * | pixGetEdgeProfile (PIX *pixs, l_int32 side, const char *debugfile) |
| l_ok | pixGetLastOffPixelInRun (PIX *pixs, l_int32 x, l_int32 y, l_int32 direction, l_int32 *ploc) |
| l_int32 | pixGetLastOnPixelInRun (PIX *pixs, l_int32 x, l_int32 y, l_int32 direction, l_int32 *ploc) |
Sobel edge detecting filter
PIX *pixSobelEdgeFilter()
Two-sided edge gradient filter
PIX *pixTwoSidedEdgeFilter()
Measurement of edge smoothness
l_int32 pixMeasureEdgeSmoothness()
NUMA *pixGetEdgeProfile()
l_int32 pixGetLastOffPixelInRun()
l_int32 pixGetLastOnPixelInRun()
The Sobel edge detector uses these two simple gradient filters.
1 2 1 1 0 -1
0 0 0 2 0 -2
-1 -2 -1 1 0 -1
(horizontal) (vertical)
To use both the vertical and horizontal filters, set the orientation
flag to L_ALL_EDGES; this sums the abs. value of their outputs,
clipped to 255.
See comments below for displaying the resulting image with
the edges dark, both for 8 bpp and 1 bpp.
Definition in file edge.c.
| [in] | pixs | 1 bpp |
| [in] | side | L_FROM_LEFT, L_FROM_RIGHT, L_FROM_TOP, L_FROM_BOT |
| [in] | debugfile | [optional] displays constructed edge; use NULL for no output |
Definition at line 383 of file edge.c.
References L_FROM_BOT, L_FROM_LEFT, L_FROM_RIGHT, and L_FROM_TOP.
Referenced by pixMeasureEdgeSmoothness().
| l_ok pixGetLastOffPixelInRun | ( | PIX * | pixs, |
| l_int32 | x, | ||
| l_int32 | y, | ||
| l_int32 | direction, | ||
| l_int32 * | ploc ) |
| l_int32 pixGetLastOnPixelInRun | ( | PIX * | pixs, |
| l_int32 | x, | ||
| l_int32 | y, | ||
| l_int32 | direction, | ||
| l_int32 * | ploc ) |
| l_ok pixMeasureEdgeSmoothness | ( | PIX * | pixs, |
| l_int32 | side, | ||
| l_int32 | minjump, | ||
| l_int32 | minreversal, | ||
| l_float32 * | pjpl, | ||
| l_float32 * | pjspl, | ||
| l_float32 * | prpl, | ||
| const char * | debugfile ) |
| [in] | pixs | 1 bpp |
| [in] | side | L_FROM_LEFT, L_FROM_RIGHT, L_FROM_TOP, L_FROM_BOT |
| [in] | minjump | minimum jump to be counted; >= 1 |
| [in] | minreversal | minimum reversal size for new peak or valley |
| [out] | pjpl | [optional] jumps/length: number of jumps, normalized to length of component side |
| [out] | pjspl | [optional] jumpsum/length: sum of all sufficiently large jumps, normalized to length of component side |
| [out] | prpl | [optional] reversals/length: number of peak-to-valley or valley-to-peak reversals, normalized to length of component side |
| [in] | debugfile | [optional] displays constructed edge; use NULL for no output |
Notes:
(1) This computes three measures of smoothness of the edge of a
connected component:
* jumps/length: (jpl) the number of jumps of size >= minjump,
normalized to the length of the side
* jump sum/length: (jspl) the sum of all jump lengths of
size >= minjump, normalized to the length of the side
* reversals/length: (rpl) the number of peak <--> valley
reversals, using minreverse as a minimum deviation of
the peak or valley from its preceding extremum,
normalized to the length of the side
(2) The input pix should be a single connected component, but
this is not required.
Definition at line 308 of file edge.c.
References L_FROM_BOT, L_FROM_LEFT, L_FROM_RIGHT, L_FROM_TOP, and pixGetEdgeProfile().
| [in] | pixs | 8 bpp; no colormap |
| [in] | orientflag | L_HORIZONTAL_EDGES, L_VERTICAL_EDGES, L_ALL_EDGES |
Notes:
(1) Invert pixd to see larger gradients as darker (grayscale).
(2) To generate a binary image of the edges, threshold
the result using pixThresholdToBinary(). If the high
edge values are to be fg (1), invert after running
pixThresholdToBinary().
(3) Label the pixels as follows:
1 4 7
2 5 8
3 6 9
Read the data incrementally across the image and unroll
the loop.
(4) This runs at about 45 Mpix/sec on a 3 GHz processor.
Definition at line 94 of file edge.c.
References GET_DATA_BYTE, L_ALL_EDGES, L_HORIZONTAL_EDGES, L_VERTICAL_EDGES, and SET_DATA_BYTE.
| [in] | pixs | 8 bpp; no colormap |
| [in] | orientflag | L_HORIZONTAL_EDGES, L_VERTICAL_EDGES |
Notes:
(1) For detecting vertical edges, this considers the
difference of the central pixel from those on the left
and right. For situations where the gradient is the same
sign on both sides, this computes and stores the minimum
(absolute value of the) difference. The reason for
checking the sign is that we are looking for pixels within
a transition. By contrast, for single pixel noise, the pixel
value is either larger than or smaller than its neighbors,
so the gradient would change direction on each side. Horizontal
edges are handled similarly, looking for vertical gradients.
(2) To generate a binary image of the edges, threshold
the result using pixThresholdToBinary(). If the high
edge values are to be fg (1), invert after running
pixThresholdToBinary().
(3) This runs at about 60 Mpix/sec on a 3 GHz processor.
It is about 30% faster than Sobel, and the results are
similar.
Definition at line 200 of file edge.c.
References GET_DATA_BYTE, L_HORIZONTAL_EDGES, L_VERTICAL_EDGES, and SET_DATA_BYTE.
1.12.0