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more canny cleanups

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This commit is contained in:
John Cupitt 2018-03-17 22:42:40 +00:00
parent b4181054b2
commit 6d570ef0ff
1 changed files with 5 additions and 38 deletions
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43
libvips/convolution/canny.c
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@ -101,8 +101,7 @@ vips_canny_gradient( VipsImage *in, VipsImage **Gx, VipsImage **Gy )
static VipsPel vips_canny_polar_atan2[256];
/* For the uchar path, gx/gy are -128 to +127, and we need -8 to +7 for the
* atan2 LUT. Try "256 * (VIPS_DEG( atan2( gx, gy ) ) + 360) / 360;" to test
* the LUT.
* atan2 LUT.
*
* For G, we should calculate sqrt( gx * gx + gy * gy ), however we are only
* interested in relative magnitude (max of sqrt), so we can skip the sqrt
@ -141,7 +140,7 @@ static VipsPel vips_canny_polar_atan2[256];
double gy = tp2[band]; \
double theta = VIPS_DEG( atan2( gx, gy ) ); \
\
tq[0] = (gx * gx + gy * gy) / 512.0; \
tq[0] = (gx * gx + gy * gy + 256.0) / 512.0; \
tq[1] = 256.0 * fmod( theta + 360.0, 360.0 ) / 360.0; \
\
tq += 2; \
@ -241,38 +240,6 @@ vips_canny_polar( VipsImage **args, VipsImage **out )
return( 0 );
}
/* Set G to 0 if it's not the local maxima in the direction of the gradient.
*/
#define THIN_UCHAR { \
for( x = 0; x < r->width; x++ ) { \
for( band = 0; band < out_bands; band++ ) { \
int G = p[lsk + psk]; \
int theta = p[lsk + psk + 1]; \
int low_theta = (theta / 32) & 0x7; \
int high_theta = (low_theta + 1) & 0x7; \
int residual = theta - low_theta * 32; \
int lowa = p[offset[low_theta]]; \
int lowb = p[offset[high_theta]]; \
int low = (lowa * (32 - residual) + \
lowb * residual) / 32; \
int higha = p[offset[(low_theta + 4) & 0x7]]; \
int highb = p[offset[(high_theta + 4) & 0x7]]; \
int high = (higha * (32 - residual) + \
highb * residual) / 32; \
\
if( G <= low || \
G < high ) \
G = 0; \
\
q[band] = G; \
\
p += 2; \
} \
\
q += out_bands; \
} \
}
#define THIN( TYPE ) { \
TYPE *tp = (TYPE *) p; \
TYPE *tq = (TYPE *) q; \
@ -359,7 +326,6 @@ vips_canny_thin_generate( VipsRegion *or,
switch( im->BandFmt ) {
case VIPS_FORMAT_UCHAR:
//THIN_UCHAR;
THIN( unsigned char );
break;
@ -507,8 +473,9 @@ vips_canny_init( VipsCanny *canny )
* * @sigma: %gdouble, sigma for gaussian blur
*
* Find edges by Canny's method: The maximum of the derivative of the gradient
* in the direction of the gradient. This operation will only work well on
* 8-bit luminance images.
* in the direction of the gradient. Output is float, except for uchar input,
* where output is uchar, and double input, where output is double. Non-complex
* images only.
*
* Use @sigma to control the scale over which gradient is measured. 1.4 is
* usually a good value.