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gimp/plug-ins/gfig/gfig-grid.c

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/*
* Copyright (C) 1995 Spencer Kimball and Peter Mattis
*
* This is a plug-in for GIMP.
*
* Generates images containing vector type drawings.
*
* Copyright (C) 1997 Andy Thomas alt@picnic.demon.co.uk
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include "config.h"
#include <math.h>
#include <stdlib.h>
#include <libgimp/gimp.h>
#include <libgimp/gimpui.h>
#include "gfig.h"
#include "gfig-grid.h"
#include "libgimp/stdplugins-intl.h"
/* For the isometric grid */
#define SQRT3 1.73205080756887729353 /* Square root of 3 */
#define SIN_1o6PI_RAD 0.5 /* Sine 1/6 Pi Radians */
#define COS_1o6PI_RAD SQRT3 / 2 /* Cosine 1/6 Pi Radians */
#define TAN_1o6PI_RAD 1 / SQRT3 /* Tangent 1/6 Pi Radians == SIN / COS */
#define RECIP_TAN_1o6PI_RAD SQRT3 /* Reciprocal of Tangent 1/6 Pi Radians */
gint grid_gc_type = GFIG_NORMAL_GC;
static void draw_grid_polar (cairo_t *drawgc);
static void draw_grid_sq (cairo_t *drawgc);
static void draw_grid_iso (cairo_t *drawgc);
static cairo_t * gfig_get_grid_gc (cairo_t *cr,
GtkWidget *widget,
gint gctype);
static void find_grid_pos_polar (GdkPoint *p,
GdkPoint *gp);
/********** PrimeFactors for Shaneyfelt-style Polar Grid **********
* Quickly factor any number up to 17160
* Correctly factors numbers up to 131 * 131 - 1
*/
typedef struct
{
gint product;
gint remaining;
gint current;
gint next;
gint index;
} PrimeFactors;
static gchar primes[] = { 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,
59,61,67,71,73,79,83,89,97,101,103,107,109,113,127 };
#define PRIMES_MAX_INDEX 30
static gint
prime_factors_get (PrimeFactors *this)
{
this->current = this->next;
while (this->index <= PRIMES_MAX_INDEX)
{
if (this->remaining % primes[this->index] == 0) /* divisible */
{
this->remaining /= primes[this->index];
this->next = primes[this->index];
return this->current;
}
this->index++;
}
this->next = this->remaining;
this->remaining = 1;
return this->current;
}
static gint
prime_factors_lookahead (PrimeFactors *this)
{
return this->next;
}
static void
prime_factors_reset (PrimeFactors *this)
{
this->remaining = this->product;
this->index = 0;
prime_factors_get (this);
}
static PrimeFactors *
prime_factors_new (gint n)
{
PrimeFactors *this = g_new (PrimeFactors, 1);
this->product = n;
prime_factors_reset (this);
return this;
}
static void
prime_factors_delete (PrimeFactors* this)
{
g_free (this);
}
/********** ********** **********/
static gdouble
sector_size_at_radius (gdouble inner_radius)
{
PrimeFactors *factors = prime_factors_new (selvals.opts.grid_sectors_desired);
gint current_sectors = 1;
gdouble sector_size = 2 * G_PI / current_sectors;
while ((current_sectors < selvals.opts.grid_sectors_desired)
&& (inner_radius*sector_size
> (prime_factors_lookahead (factors) *
selvals.opts.grid_granularity)))
{
current_sectors *= prime_factors_get (factors);
sector_size = 2 * G_PI / current_sectors;
}
prime_factors_delete(factors);
return sector_size;
}
static void
find_grid_pos_polar (GdkPoint *p,
GdkPoint *gp)
{
gdouble cx = preview_width / 2.0;
gdouble cy = preview_height / 2.0;
gdouble px = p->x - cx;
gdouble py = p->y - cy;
gdouble x = 0;
gdouble y = 0;
gdouble r = sqrt (SQR (px) + SQR (py));
if (r >= selvals.opts.grid_radius_min * 0.5)
{
gdouble t;
gdouble sectorSize;
r = selvals.opts.grid_radius_interval
* (gint) (0.5 + ((r - selvals.opts.grid_radius_min) /
selvals.opts.grid_radius_interval))
+ selvals.opts.grid_radius_min;
t = atan2 (py, px) + 2 * G_PI;
sectorSize = sector_size_at_radius (r);
t = selvals.opts.grid_rotation
+ (gint) (0.5 + ((t - selvals.opts.grid_rotation) / sectorSize))
* sectorSize;
x = r * cos (t);
y = r * sin (t);
}
gp->x = x + cx;
gp->y = y + cy;
}
/* find_grid_pos - Given an x, y point return the grid position of it */
/* return the new position in the passed point */
void
gfig_grid_colors (GtkWidget *widget)
{
}
void
find_grid_pos (GdkPoint *p,
GdkPoint *gp,
guint is_butt3)
{
gint16 x = p->x;
gint16 y = p->y;
static GdkPoint cons_pnt;
if (selvals.opts.gridtype == RECT_GRID)
{
if (p->x % selvals.opts.gridspacing > selvals.opts.gridspacing/2)
x += selvals.opts.gridspacing;
if (p->y % selvals.opts.gridspacing > selvals.opts.gridspacing/2)
y += selvals.opts.gridspacing;
gp->x = (x/selvals.opts.gridspacing)*selvals.opts.gridspacing;
gp->y = (y/selvals.opts.gridspacing)*selvals.opts.gridspacing;
if (is_butt3)
{
if (abs (gp->x - cons_pnt.x) < abs (gp->y - cons_pnt.y))
gp->x = cons_pnt.x;
else
gp->y = cons_pnt.y;
}
else
{
/* Store the point since might be used later */
cons_pnt = *gp; /* Structure copy */
}
}
else if (selvals.opts.gridtype == POLAR_GRID)
{
find_grid_pos_polar (p,gp);
}
else if (selvals.opts.gridtype == ISO_GRID)
{
/*
* This really needs a picture to show the math...
*
* Consider an isometric grid with one of the sets of lines
* parallel to the y axis (vertical alignment). Further define
* that the origin of a Cartesian grid is at a isometric vertex.
* For simplicity consider the first quadrant only.
*
* - Let one line segment between vertices be r
* - Define the value of r as the grid spacing
* - Assign an integer n identifier to each vertical grid line
* along the x axis. with n=0 being the y axis. n can be any
* integer
* - Let m to be any integer
* - Let h be the spacing between vertical grid lines measured
* along the x axis. It follows from the isometric grid that
* h has a value of r * COS(1/6 Pi Rad)
*
* Consider a Vertex V at the Cartesian location [Xv, Yv]
*
* It follows that vertices belong to the set...
* V[Xv, Yv] = [ [ n * h ] ,
* [ m * r + ( 0.5 * r (n % 2) ) ] ]
* for all integers n and m
*
* Who cares? Me. It's useful in solving this problem:
* Consider an arbitrary point P[Xp,Yp], find the closest vertex
* in the set V.
*
* Restated this problem is "find values for m and n that are
* drive V closest to P"
*
* A Solution method (there may be a better one?):
*
* Step 1) bound n to the two closest values for Xp
* n_lo = (int) (Xp / h)
* n_hi = n_lo + 1
*
* Step 2) Consider the two closes vertices for each n_lo and
* n_hi. The further of the vertices in each pair can
* readily be discarded.
*
* m_lo_n_lo = (int) ( (Yp / r) - 0.5 (n_lo % 2) )
* m_hi_n_lo = m_lo_n_lo + 1
*
* m_lo_n_hi = (int) ( (Yp / r) - 0.5 (n_hi % 2) )
* m_hi_n_hi = m_hi_n_hi
*
* Step 3) compute the distance from P to V1 and V2. Snap to the
* closer point.
*/
gint n_lo;
gint n_hi;
gint m_lo_n_lo;
gint m_hi_n_lo;
gint m_lo_n_hi;
gint m_hi_n_hi;
gint m_n_lo;
gint m_n_hi;
gdouble r;
gdouble h;
gint x1;
gint x2;
gint y1;
gint y2;
r = selvals.opts.gridspacing;
h = COS_1o6PI_RAD * r;
n_lo = (gint) x / h;
n_hi = n_lo + 1;
/* evaluate m candidates for n_lo */
m_lo_n_lo = (gint) ((y / r) - 0.5 * (n_lo % 2));
m_hi_n_lo = m_lo_n_lo + 1;
/* figure out which is the better candidate */
if (fabs ((m_lo_n_lo * r + (0.5 * r * (n_lo % 2))) - y) <
fabs ((m_hi_n_lo * r + (0.5 * r * (n_lo % 2))) - y))
{
m_n_lo = m_lo_n_lo;
}
else
{
m_n_lo = m_hi_n_lo;
}
/* evaluate m candidates for n_hi */
m_lo_n_hi = (gint) ( (y / r) - 0.5 * (n_hi % 2) );
m_hi_n_hi = m_lo_n_hi + 1;
/* figure out which is the better candidate */
if (fabs((m_lo_n_hi * r + (0.5 * r * (n_hi % 2))) - y) <
fabs((m_hi_n_hi * r + (0.5 * r * (n_hi % 2))) - y))
{
m_n_hi = m_lo_n_hi;
}
else
{
m_n_hi = m_hi_n_hi;
}
/* Now, which is closer to [x,y]? we can use a somewhat
* abbreviated form of the distance formula since we only care
* about relative values.
*/
x1 = (gint) (n_lo * h);
y1 = (gint) (m_n_lo * r + (0.5 * r * (n_lo % 2)));
x2 = (gint) (n_hi * h);
y2 = (gint) (m_n_hi * r + (0.5 * r * (n_hi % 2)));
if (((x - x1) * (x - x1) + (y - y1) * (y - y1)) <
((x - x2) * (x - x2) + (y - y2) * (y - y2)))
{
gp->x = x1;
gp->y = y1;
}
else
{
gp->x = x2;
gp->y = y2;
}
}
}
static void
draw_grid_polar (cairo_t *cr)
{
gdouble inner_radius;
gdouble outer_radius;
gdouble max_radius = sqrt (SQR (preview_width) + SQR (preview_height));
gint current_sectors = 1;
PrimeFactors *factors = prime_factors_new (selvals.opts.grid_sectors_desired);
for (inner_radius = 0, outer_radius = selvals.opts.grid_radius_min;
outer_radius <= max_radius;
inner_radius = outer_radius, outer_radius += selvals.opts.grid_radius_interval)
{
gdouble t;
gdouble sector_size = 2 * G_PI / current_sectors;
cairo_arc (cr,
0.5 + preview_width / 2.0,
0.5 + preview_height / 2.0,
outer_radius, 0, 2 * G_PI);
cairo_stroke (cr);
while ((current_sectors < selvals.opts.grid_sectors_desired)
&& (inner_radius * sector_size
> prime_factors_lookahead (factors) * selvals.opts.grid_granularity ))
{
current_sectors *= prime_factors_get (factors);
sector_size = 2 * G_PI / current_sectors;
}
for (t = 0 ; t < 2 * G_PI ; t += sector_size)
{
gdouble normal_x = cos (selvals.opts.grid_rotation+t);
gdouble normal_y = sin (selvals.opts.grid_rotation+t);
cairo_move_to (cr,
0.5 + (preview_width / 2.0 + inner_radius * normal_x),
0.5 + (preview_height / 2.0 - inner_radius * normal_y));
cairo_line_to (cr,
0.5 + (preview_width / 2.0 + outer_radius * normal_x),
0.5 + (preview_height / 2.0 - outer_radius * normal_y));
cairo_stroke (cr);
}
}
prime_factors_delete (factors);
}
static void
draw_grid_sq (cairo_t *cr)
{
gint step;
gint loop;
/* Draw the horizontal lines */
step = selvals.opts.gridspacing;
for (loop = 0 ; loop < preview_height ; loop += step)
{
cairo_move_to (cr, 0 + .5, loop + .5);
cairo_line_to (cr, preview_width + .5, loop + .5);
}
/* Draw the vertical lines */
for (loop = 0 ; loop < preview_width ; loop += step)
{
cairo_move_to (cr, loop + .5, 0 + .5);
cairo_line_to (cr, loop + .5, preview_height + .5);
}
cairo_stroke (cr);
}
static void
draw_grid_iso (cairo_t *cr)
{
/* vstep is an int since it's defined from grid size */
gint vstep;
gdouble loop;
gdouble hstep;
gdouble diagonal_start;
gdouble diagonal_end;
gdouble diagonal_width;
gdouble diagonal_height;
vstep = selvals.opts.gridspacing;
hstep = selvals.opts.gridspacing * COS_1o6PI_RAD;
/* Draw the vertical lines - These are easy */
for (loop = 0 ; loop < preview_width ; loop += hstep)
{
cairo_move_to (cr, loop, 0);
cairo_line_to (cr, loop, preview_height);
}
cairo_stroke (cr);
/* draw diag lines at a Theta of +/- 1/6 Pi Rad */
diagonal_start = -(((int)preview_width * TAN_1o6PI_RAD) - (((int)(preview_width * TAN_1o6PI_RAD)) % vstep));
diagonal_end = preview_height + (preview_width * TAN_1o6PI_RAD);
diagonal_end -= ((int)diagonal_end) % vstep;
diagonal_width = preview_width;
diagonal_height = preview_width * TAN_1o6PI_RAD;
/* Draw diag lines */
for (loop = diagonal_start ; loop < diagonal_end ; loop += vstep)
{
cairo_move_to (cr, 0, loop);
cairo_line_to (cr, diagonal_width, loop + diagonal_height);
cairo_move_to (cr, 0, loop);
cairo_line_to (cr, diagonal_width, loop - diagonal_height);
}
cairo_stroke (cr);
}
static cairo_t *
gfig_get_grid_gc (cairo_t *cr, GtkWidget *w, gint gctype)
{
switch (gctype)
{
default:
case GFIG_NORMAL_GC:
cairo_set_source_rgb (cr, .92, .92, .92);
break;
case GFIG_BLACK_GC:
cairo_set_source_rgb (cr, 0., 0., 0.);
break;
case GFIG_WHITE_GC:
cairo_set_source_rgb (cr, 1., 1., 1.);
break;
case GFIG_GREY_GC:
cairo_set_source_rgb (cr, .5, .5, .5);
break;
case GFIG_DARKER_GC:
cairo_set_source_rgb (cr, .25, .25, .25);
break;
case GFIG_LIGHTER_GC:
cairo_set_source_rgb (cr, .75, .75, .75);
break;
case GFIG_VERY_DARK_GC:
cairo_set_source_rgb (cr, .125, .125, .125);
break;
}
return cr;
}
void
draw_grid (cairo_t *cr)
{
/* Get the size of the preview and calc where the lines go */
/* Draw in prelight to start with... */
/* Always start in the upper left corner for rect.
*/
if ((preview_width < selvals.opts.gridspacing &&
preview_height < selvals.opts.gridspacing))
{
/* Don't draw if they don't fit */
return;
}
if (selvals.opts.drawgrid)
gfig_get_grid_gc (cr, gfig_context->preview, grid_gc_type);
else
return;
cairo_set_line_width (cr, 1.);
if (selvals.opts.gridtype == RECT_GRID)
draw_grid_sq (cr);
else if (selvals.opts.gridtype == POLAR_GRID)
draw_grid_polar (cr);
else if (selvals.opts.gridtype == ISO_GRID)
draw_grid_iso (cr);
}
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