1 /*
2 * Transforming single items
3 *
4 * Authors:
5 * Lauris Kaplinski <lauris@kaplinski.com>
6 * Frank Felfe <innerspace@iname.com>
7 * bulia byak <buliabyak@gmail.com>
8 * Johan Engelen <goejendaagh@zonnet.nl>
9 * Abhishek Sharma
10 *
11 * Copyright (C) 1999-2008 authors
12 *
13 * Released under GNU GPL, read the file 'COPYING' for more information
14 */
16 #include <2geom/transforms.h>
17 #include "sp-item.h"
19 void
20 sp_item_rotate_rel(SPItem *item, Geom::Rotate const &rotation)
21 {
22 Geom::Point center = item->getCenter();
23 Geom::Translate const s(item->getCenter());
24 Geom::Matrix affine = Geom::Matrix(s).inverse() * Geom::Matrix(rotation) * Geom::Matrix(s);
26 // Rotate item.
27 item->set_i2d_affine(item->i2d_affine() * (Geom::Matrix)affine);
28 // Use each item's own transform writer, consistent with sp_selection_apply_affine()
29 item->doWriteTransform(SP_OBJECT_REPR(item), item->transform);
31 // Restore the center position (it's changed because the bbox center changed)
32 if (item->isCenterSet()) {
33 item->setCenter(center * affine);
34 item->updateRepr();
35 }
36 }
38 void
39 sp_item_scale_rel (SPItem *item, Geom::Scale const &scale)
40 {
41 Geom::OptRect bbox = item->getBboxDesktop();
42 if (bbox) {
43 Geom::Translate const s(bbox->midpoint()); // use getCenter?
44 item->set_i2d_affine(item->i2d_affine() * s.inverse() * scale * s);
45 item->doWriteTransform(SP_OBJECT_REPR(item), item->transform);
46 }
47 }
49 void
50 sp_item_skew_rel (SPItem *item, double skewX, double skewY)
51 {
52 Geom::Point center = item->getCenter();
53 Geom::Translate const s(item->getCenter());
55 Geom::Matrix const skew(1, skewY, skewX, 1, 0, 0);
56 Geom::Matrix affine = Geom::Matrix(s).inverse() * skew * Geom::Matrix(s);
58 item->set_i2d_affine(item->i2d_affine() * affine);
59 item->doWriteTransform(SP_OBJECT_REPR(item), item->transform);
61 // Restore the center position (it's changed because the bbox center changed)
62 if (item->isCenterSet()) {
63 item->setCenter(center * affine);
64 item->updateRepr();
65 }
66 }
68 void sp_item_move_rel(SPItem *item, Geom::Translate const &tr)
69 {
70 item->set_i2d_affine(item->i2d_affine() * tr);
72 item->doWriteTransform(SP_OBJECT_REPR(item), item->transform);
73 }
75 /*
76 ** Returns the matrix you need to apply to an object with given visual bbox and strokewidth to
77 scale/move it to the new visual bbox x0/y0/x1/y1. Takes into account the "scale stroke"
78 preference value passed to it. Has to solve a quadratic equation to make sure
79 the goal is met exactly and the stroke scaling is obeyed.
80 */
82 Geom::Matrix
83 get_scale_transform_with_stroke (Geom::Rect const &bbox_param, gdouble strokewidth, bool transform_stroke, gdouble x0, gdouble y0, gdouble x1, gdouble y1)
84 {
85 Geom::Rect bbox (bbox_param);
87 Geom::Matrix p2o = Geom::Translate (-bbox.min());
88 Geom::Matrix o2n = Geom::Translate (x0, y0);
90 Geom::Matrix scale = Geom::Scale (1, 1); // scale component
91 Geom::Matrix unbudge = Geom::Translate (0, 0); // move component to compensate for the drift caused by stroke width change
93 gdouble w0 = bbox[Geom::X].extent(); // will return a value >= 0, as required further down the road
94 gdouble h0 = bbox[Geom::Y].extent();
95 gdouble w1 = x1 - x0; // can have any sign
96 gdouble h1 = y1 - y0;
97 gdouble r0 = strokewidth;
99 if (bbox.hasZeroArea()) {
100 Geom::Matrix move = Geom::Translate(x0 - bbox.min()[Geom::X], y0 - bbox.min()[Geom::Y]);
101 return (move); // cannot scale from empty boxes at all, so only translate
102 }
104 Geom::Matrix direct = Geom::Scale(w1 / w0, h1 / h0);
106 if (fabs(w0 - r0) < 1e-6 || fabs(h0 - r0) < 1e-6 || (!transform_stroke && (fabs(w1 - r0) < 1e-6 || fabs(h1 - r0) < 1e-6))) {
107 return (p2o * direct * o2n); // can't solve the equation: one of the dimensions is equal to stroke width, so return the straightforward scaler
108 }
110 int flip_x = (w1 > 0) ? 1 : -1;
111 int flip_y = (h1 > 0) ? 1 : -1;
113 // w1 and h1 will be negative when mirroring, but if so then e.g. w1-r0 won't make sense
114 // Therefore we will use the absolute values from this point on
115 w1 = fabs(w1);
116 h1 = fabs(h1);
117 r0 = fabs(r0);
118 // w0 and h0 will always be positive due to the definition extent()
120 gdouble ratio_x = (w1 - r0) / (w0 - r0);
121 gdouble ratio_y = (h1 - r0) / (h0 - r0);
123 Geom::Matrix direct_constant_r = Geom::Scale(flip_x * ratio_x, flip_y * ratio_y);
125 if (transform_stroke && r0 != 0 && r0 != NR_HUGE) { // there's stroke, and we need to scale it
126 // These coefficients are obtained from the assumption that scaling applies to the
127 // non-stroked "shape proper" and that stroke scale is scaled by the expansion of that
128 // matrix. We're trying to solve this equation:
129 // r1 = r0 * sqrt (((w1-r0)/(w0-r0))*((h1-r0)/(h0-r0)))
130 // The operant of the sqrt() must be positive, which is ensured by the fabs() a few lines above
131 gdouble A = -w0*h0 + r0*(w0 + h0);
132 gdouble B = -(w1 + h1) * r0*r0;
133 gdouble C = w1 * h1 * r0*r0;
134 if (B*B - 4*A*C > 0) {
135 gdouble r1 = fabs((-B - sqrt(B*B - 4*A*C))/(2*A));
136 //gdouble r2 = (-B + sqrt (B*B - 4*A*C))/(2*A);
137 //std::cout << "r0" << r0 << " r1" << r1 << " r2" << r2 << "\n";
138 //
139 // If w1 < 0 then the scale will be wrong if we just do
140 // gdouble scale_x = (w1 - r1)/(w0 - r0);
141 // Here we also need the absolute values of w0, w1, h0, h1, and r1
142 gdouble scale_x = (w1 - r1)/(w0 - r0);
143 gdouble scale_y = (h1 - r1)/(h0 - r0);
144 scale *= Geom::Scale(flip_x * scale_x, flip_y * scale_y);
145 unbudge *= Geom::Translate (-flip_x * 0.5 * (r0 * scale_x - r1), -flip_y * 0.5 * (r0 * scale_y - r1));
146 } else {
147 scale *= direct;
148 }
149 } else {
150 if (r0 == 0 || r0 == NR_HUGE) { // no stroke to scale
151 scale *= direct;
152 } else {// nonscaling strokewidth
153 scale *= direct_constant_r;
154 unbudge *= Geom::Translate (flip_x * 0.5 * r0 * (1 - ratio_x), flip_y * 0.5 * r0 * (1 - ratio_y));
155 }
156 }
158 return (p2o * scale * unbudge * o2n);
159 }
161 Geom::Rect
162 get_visual_bbox (Geom::OptRect const &initial_geom_bbox, Geom::Matrix const &abs_affine, gdouble const initial_strokewidth, bool const transform_stroke)
163 {
165 g_assert(initial_geom_bbox);
167 // Find the new geometric bounding box; Do this by transforming each corner of
168 // the initial geometric bounding box individually and fitting a new boundingbox
169 // around the transformerd corners
170 Geom::Point const p0 = Geom::Point(initial_geom_bbox->corner(0)) * abs_affine;
171 Geom::Rect new_geom_bbox(p0, p0);
172 for (unsigned i = 1 ; i < 4 ; i++) {
173 new_geom_bbox.expandTo(Geom::Point(initial_geom_bbox->corner(i)) * abs_affine);
174 }
176 Geom::Rect new_visual_bbox = new_geom_bbox;
177 if (initial_strokewidth > 0 && initial_strokewidth < NR_HUGE) {
178 if (transform_stroke) {
179 // scale stroke by: sqrt (((w1-r0)/(w0-r0))*((h1-r0)/(h0-r0))) (for visual bboxes, see get_scale_transform_with_stroke)
180 // equals scaling by: sqrt ((w1/w0)*(h1/h0)) for geometrical bboxes
181 // equals scaling by: sqrt (area1/area0) for geometrical bboxes
182 gdouble const new_strokewidth = initial_strokewidth * sqrt (new_geom_bbox.area() / initial_geom_bbox->area());
183 new_visual_bbox.expandBy(0.5 * new_strokewidth);
184 } else {
185 // Do not transform the stroke
186 new_visual_bbox.expandBy(0.5 * initial_strokewidth);
187 }
188 }
190 return new_visual_bbox;
191 }
193 /*
194 Local Variables:
195 mode:c++
196 c-file-style:"stroustrup"
197 c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
198 indent-tabs-mode:nil
199 fill-column:99
200 End:
201 */
202 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :