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much better accuracy for small masks

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This commit is contained in:
John Cupitt 2011-06-04 12:39:54 +01:00
parent 56d8f75500
commit 70dc170d97
1 changed files with 13 additions and 38 deletions
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51
libvips/convolution/im_aconv.c
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@ -52,30 +52,6 @@
- are we handling mask offset correctly?
- relatively large error for small int masks, can we tune for this
vips im_gauss_imask_sep x.con 4.5 0.1
21 1 222 0
2 3 4 6 8 11 13 16 18 20 20 20 18 16 13 11 8 6 4 3 2
graphs as:
depth = 2, n_layers = 10
lines:
0 - 1 x ######## 9 .. 12
1 - 1 x ############## 8 .. 13
2 - 2 x ################## 7 .. 14
3 - 1 x ######################## 6 .. 15
4 - 1 x ############################ 5 .. 16
5 - 1 x ################################## 4 .. 17
6 - 1 x ######################################## 3 .. 18
7 - 1 x ############################################ 2 .. 19
8 - 1 x ##################################################### 0 .. 20
why so lop-sided?
*/
/* Show sample pixels as they are transformed.
@ -153,12 +129,12 @@ static int
line_end( Lines *lines, int x )
{
lines->end[lines->n_lines] = x;
lines->n_lines += 1;
if( lines->n_lines >= MAX_LINES ) {
if( lines->n_lines >= MAX_LINES - 1 ) {
vips_error( "im_aconv", "%s", _( "mask too complex" ) );
return( -1 );
}
lines->n_lines += 1;
return( 0 );
}
@ -228,6 +204,10 @@ lines_new( IMAGE *in, IMAGE *out, DOUBLEMASK *mask, int n_layers )
for( z = 0; z < n_layers; z++ ) {
double y = max - (1 + z) * depth;
/* y plus half depth ... ie. the layer midpoint.
*/
double y_ph = y + depth / 2;
/* Odd, but we must avoid rounding errors that make us miss 0
* in the line above.
*/
@ -243,29 +223,24 @@ lines_new( IMAGE *in, IMAGE *out, DOUBLEMASK *mask, int n_layers )
/* The vertical line from mask[z] to 0 is inside. Is
* our current square (x, y) part of that line?
*/
if( (y_positive && mask->coeff[x] > y + depth / 2) ||
(!y_positive && mask->coeff[x] < y + depth / 2) ) {
/* (x, y) is inside.
*/
if( (y_positive && mask->coeff[x] >= y_ph) ||
(!y_positive && mask->coeff[x] <= y_ph) ) {
if( !inside ) {
line_start( lines,
x, y_positive ? 1 : -1 );
line_start( lines, x,
y_positive ? 1 : -1 );
inside = 1;
}
}
else {
/* (x, y) is outside.
*/
if( inside ) {
if( line_end( lines, x ) )
return( NULL );
line_end( lines, x );
inside = 0;
}
}
}
if( inside &&
line_end( lines, mask->xsize - 1 ) )
line_end( lines, width ) )
return( NULL );
}
@ -331,7 +306,7 @@ lines_new( IMAGE *in, IMAGE *out, DOUBLEMASK *mask, int n_layers )
for( z = 0; z < lines->n_lines; z++ ) {
printf( "%3d - %2d x ", z, lines->factor[z] );
for( x = 0; x < 55; x++ ) {
int rx = x * width / 55;
int rx = x * (width + 1) / 55;
if( rx >= lines->start[z] && rx < lines->end[z] )
printf( "#" );