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better smoothing for perlin

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This commit is contained in:
John Cupitt 2016-07-24 12:58:45 +01:00
parent c469bb3983
commit 6db9a2fdf9
2 changed files with 38 additions and 7 deletions
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2
TODO
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@ -1,5 +1,3 @@
- need better interpolation in the perlin generator?
- add tests for perlin and worley noise generators
- add more webp tests to py suite

43
libvips/create/perlin.c
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@ -54,6 +54,7 @@ typedef struct _VipsPerlin {
int width;
int height;
int cell_size;
gboolean uchar;
int cells_across;
int cells_down;
@ -182,6 +183,16 @@ vips_perlin_start( VipsImage *out, void *a, void *b )
return( seq );
}
/* Smooth linear interpolation, 0 <= x <= 1.
*
* https://en.wikipedia.org/wiki/Smoothstep
*/
static float
smootherstep( float x )
{
return( x * x * x * (x * (x * 6 - 15) + 10) );
}
static int
vips_perlin_gen( VipsRegion *or, void *vseq, void *a, void *b,
gboolean *stop )
@ -193,7 +204,9 @@ vips_perlin_gen( VipsRegion *or, void *vseq, void *a, void *b,
int x, y;
for( y = 0; y < r->height; y++ ) {
float *q = (float *) VIPS_REGION_ADDR( or, r->left, r->top + y );
float *fq = (float *)
VIPS_REGION_ADDR( or, r->left, r->top + y );
VipsPel *q = (VipsPel *) fq;
for( x = 0; x < r->width; x++ ) {
int cs = perlin->cell_size;
@ -201,9 +214,12 @@ vips_perlin_gen( VipsRegion *or, void *vseq, void *a, void *b,
int cell_y = (r->top + y) / cs;
float dx = (x + r->left - cell_x * cs) / (float) cs;
float dy = (y + r->top - cell_y * cs) / (float) cs;
float sx = smootherstep( dx );
float sy = smootherstep( dy );
float n0, n1;
float ix0, ix1;
float p;
if( cell_x != seq->cell_x ||
cell_y != seq->cell_y ) {
@ -215,13 +231,18 @@ vips_perlin_gen( VipsRegion *or, void *vseq, void *a, void *b,
n0 = -dx * seq->gx[0] + -dy * seq->gy[0];
n1 = (1 - dx) * seq->gx[1] + -dy * seq->gy[1];
ix0 = (1 - dx) * n0 + dx * n1;
ix0 = n0 + sx * (n1 - n0);
n0 = -dx * seq->gx[2] + (1 - dy) * seq->gy[2];
n1 = (1 - dx) * seq->gx[3] + (1 - dy) * seq->gy[3];
ix1 = (1 - dx) * n0 + dx * n1;
ix1 = n0 + sx * (n1 - n0);
q[x] = (1 - dy) * ix0 + dy * ix1;
p = ix0 + sy * (ix1 - ix0);
if( perlin->uchar )
q[x] = 128 * p + 128;
else
fq[x] = p;
}
}
@ -248,7 +269,8 @@ vips_perlin_build( VipsObject *object )
vips_image_init_fields( create->out,
perlin->width, perlin->height, 1,
VIPS_FORMAT_FLOAT, VIPS_CODING_NONE, VIPS_INTERPRETATION_B_W,
perlin->uchar ? VIPS_FORMAT_UCHAR : VIPS_FORMAT_FLOAT,
VIPS_CODING_NONE, VIPS_INTERPRETATION_B_W,
1.0, 1.0 );
vips_image_pipelinev( create->out,
VIPS_DEMAND_STYLE_ANY, NULL );
@ -313,6 +335,13 @@ vips_perlin_class_init( VipsPerlinClass *class )
G_STRUCT_OFFSET( VipsPerlin, cell_size ),
1, VIPS_MAX_COORD, 256 );
VIPS_ARG_BOOL( class, "uchar", 4,
_( "Uchar" ),
_( "Output an unsigned char image" ),
VIPS_ARGUMENT_OPTIONAL_INPUT,
G_STRUCT_OFFSET( VipsPerlin, uchar ),
FALSE );
}
static void
@ -331,6 +360,7 @@ vips_perlin_init( VipsPerlin *perlin )
* Optional arguments:
*
* * @cell_size: %gint, size of Perlin cells
* * @uchar: output a uchar image
*
* Create a one-band float image of Perlin noise. See:
*
@ -341,6 +371,9 @@ vips_perlin_init( VipsPerlin *perlin )
*
* If @width and @height are multiples of @cell_size, the image will tessellate.
*
* Normally, output pixels are #VIPS_FORMAT_FLOAT in the range [-1, +1]. Set
* @uchar to output a uchar image with pixels in [0, 255].
*
* See also: vips_worley(), vips_fractsurf(), vips_gaussnoise().
*
* Returns: 0 on success, -1 on error