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/*
* This program source code file is part of KICAD, a free EDA CAD application.
*
* Copyright (C) 2021 Jan Sebastian Götte <kicad@jaseg.de>
* Copyright (C) 2021 KiCad Developers, see AUTHORS.txt for contributors.
*
* 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 2
* 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, you may find one here:
* http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
* or you may search the http://www.gnu.org website for the version 2 license,
* or you may write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
*/
#include <cmath>
#include <string>
#include <iostream>
#include <vector>
#include <opencv2/opencv.hpp>
#include "svg_import_util.h"
#include "vec_core.h"
#include "svg_import_defs.h"
#include "jc_voronoi.h"
using namespace svg_plugin;
using namespace std;
/* debug function */
static void dbg_show_cv_image(cv::Mat &img) {
string windowName = "Debug image";
cv::namedWindow(windowName);
cv::imshow(windowName, img);
cv::waitKey(0);
cv::destroyWindow(windowName);
}
/* From jcv voronoi README */
static void voronoi_relax_points(const jcv_diagram* diagram, jcv_point* points) {
const jcv_site* sites = jcv_diagram_get_sites(diagram);
for (int i=0; i<diagram->numsites; i++) {
const jcv_site* site = &sites[i];
jcv_point sum = site->p;
int count = 1;
const jcv_graphedge* edge = site->edges;
while (edge) {
sum.x += edge->pos[0].x;
sum.y += edge->pos[0].y;
count++;
edge = edge->next;
}
points[site->index].x = sum.x / count;
points[site->index].y = sum.y / count;
}
}
/* Render image into gerber file.
*
* This function renders an image into a number of vector primitives emulating the images grayscale brightness by
* differently sized vector shaped giving an effect similar to halftone printing used in newspapers.
*
* On a high level, this function does this in four steps:
* 1. It preprocesses the source image at the pixel level. This involves several tasks:
* 1.1. It converts the image to grayscale.
* 1.2. It scales the image up or down to match the given minimum feature size.
* 1.3. It applies a blur depending on the given minimum feature size to prevent aliasing artifacts.
* 2. It randomly spread points across the image using poisson disc sampling. This yields points that have a fairly even
* average distance to each other across the image, and that have a guaranteed minimum distance that depends on
* minimum feature size.
* 3. It calculates a voronoi map based on this set of points and it calculats the polygon shape of each cell of the
* voronoi map.
* 4. It scales each of these voronoi cell polygons to match the input images brightness at the spot covered by this
* cell.
*/
void vectorizer::vectorize_image(cairo_t *cr, const pugi::xml_node &node, double min_feature_size_px, ClipperLib::Paths &clip_path, cairo_matrix_t &viewport_matrix) {
/* Read XML node attributes */
auto x = usvg_double_attr(node, "x", 0.0);
auto y = usvg_double_attr(node, "y", 0.0);
auto width = usvg_double_attr(node, "width", 0.0);
auto height = usvg_double_attr(node, "height", 0.0);
assert (width > 0 && height > 0);
cerr << "image elem: w="<<width<<", h="<<height<<endl;
/* Read image from data:base64... URL */
string img_data = parse_data_iri(node.attribute("xlink:href").value());
if (img_data.empty()) {
cerr << "Warning: Empty or invalid image element with id \"" << node.attribute("id").value() << "\"" << endl;
return;
}
/* slightly annoying round-trip through the std:: and cv:: APIs */
vector<unsigned char> img_vec(img_data.begin(), img_data.end());
cv::Mat data_mat(img_vec, true);
cv::Mat img = cv::imdecode(data_mat, cv::ImreadModes::IMREAD_GRAYSCALE | cv::ImreadModes::IMREAD_ANYDEPTH);
data_mat.release();
if (img.empty()) {
cerr << "Warning: Could not decode content of image element with id \"" << node.attribute("id").value() << "\"" << endl;
return;
}
/* Set up target transform using SVG transform and x/y attributes */
cairo_save(cr);
apply_cairo_transform_from_svg(cr, node.attribute("transform").value());
cairo_translate(cr, x, y);
/* Adjust minimum feature size given in mm and translate into px document units in our local coordinate system. */
double f_x = min_feature_size_px, f_y = 0;
cairo_device_to_user_distance(cr, &f_x, &f_y);
min_feature_size_px = sqrt(f_x*f_x + f_y*f_y);
/* For both our debug SVG output and for the gerber output, we have to paint the image's bounding box in black as
* background for our halftone blobs. We cannot simply draw a rect here, though. Instead we have to first intersect
* the bounding box with the clip path we get from the caller, then we have to translate it into Cairo-SVG's
* document units. */
/* First, setup the bounding box rectangle in our local px coordinate space. */
ClipperLib::Path rect_path;
for (auto &elem : vector<pair<double, double>> {{0, 0}, {width, 0}, {width, height}, {0, height}}) {
double x = elem.first, y = elem.second;
cairo_user_to_device(cr, &x, &y);
rect_path.push_back({ (ClipperLib::cInt)round(x * clipper_scale), (ClipperLib::cInt)round(y * clipper_scale) });
}
/* Intersect the bounding box with the caller's clip path */
ClipperLib::Clipper c;
c.AddPath(rect_path, ClipperLib::ptSubject, /* closed */ true);
if (!clip_path.empty()) {
c.AddPaths(clip_path, ClipperLib::ptClip, /* closed */ true);
}
ClipperLib::Paths rect_out;
c.StrictlySimple(true);
c.Execute(ClipperLib::ctIntersection, rect_out, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
/* Finally, translate into Cairo-SVG's document units and draw. */
cairo_save(cr);
cairo_set_matrix(cr, &viewport_matrix);
cairo_new_path(cr);
ClipperLib::cairo::clipper_to_cairo(rect_out, cr, CAIRO_PRECISION, ClipperLib::cairo::tNone);
cairo_set_source_rgba (cr, 0.0, 0.0, 0.0, 1.0);
/* First, draw into SVG */
cairo_fill(cr);
cairo_restore(cr);
/* Second, draw into gerber. */
cairo_save(cr);
cairo_identity_matrix(cr);
for (const auto &poly : rect_out) {
/* FIXME */
//export_as_gerber(cr, poly, /* dark */ false);
}
cairo_restore(cr);
/* Set up a poisson-disc sampled point "grid" covering the image. Calculate poisson disc parameters from given
* minimum feature size. */
double grayscale_overhead = 0.8; /* fraction of distance between two adjacent cell centers that is reserved for
grayscale interpolation. Larger values -> better grayscale resolution,
larger cells. */
double center_distance = min_feature_size_px * 2.0 * (1.0 / (1.0-grayscale_overhead));
vector<d2p> *grid_centers = sample_poisson_disc(width, height, min_feature_size_px * 2.0 * 2.0);
/* TODO make these alternative grids available to callers */
//vector<d2p> *grid_centers = sample_hexgrid(width, height, center_distance);
//vector<d2p> *grid_centers = sample_squaregrid(width, height, center_distance);
/* Target factor between given min_feature_size and intermediate image pixels,
* i.e. <scale_featuresize_factor> px ^= min_feature_size */
double scale_featuresize_factor = 3.0;
/* TODO: support for preserveAspectRatio attribute */
double px_w = width / min_feature_size_px * scale_featuresize_factor;
double px_h = height / min_feature_size_px * scale_featuresize_factor;
/* Scale intermediate image (step 1.2) to have <scale_featuresize_factor> pixels per min_feature_size. */
cv::Mat scaled(cv::Size{(int)round(px_w), (int)round(px_h)}, img.type());
cv::resize(img, scaled, scaled.size(), 0, 0);
img.release();
/* Blur image with a kernel larger than our minimum feature size to avoid aliasing. */
cv::Mat blurred(scaled.size(), scaled.type());
int blur_size = (int)ceil(fmax(scaled.cols / width, scaled.rows / height) * center_distance);
cv::GaussianBlur(scaled, blurred, {blur_size, blur_size}, 0, 0);
scaled.release();
/* Calculate voronoi diagram for the grid generated above. */
jcv_diagram diagram;
memset(&diagram, 0, sizeof(jcv_diagram));
jcv_rect rect {{0.0, 0.0}, {width, height}};
jcv_point *pts = reinterpret_cast<jcv_point *>(grid_centers->data()); /* hackety hack */
jcv_diagram_generate(grid_centers->size(), pts, &rect, 0, &diagram);
/* Relax points, i.e. wiggle them around a little bit to equalize differences between cell sizes a little bit. */
voronoi_relax_points(&diagram, pts);
memset(&diagram, 0, sizeof(jcv_diagram));
jcv_diagram_generate(grid_centers->size(), pts, &rect, 0, &diagram);
/* For each voronoi cell calculated above, find the brightness of the blurred image pixel below its center. We do
* not have to average over the entire cell's area here: The blur is doing a good approximation of that while being
* simpler and faster.
*
* We do this step before generating the cell poygons below because we have to look up a cell's neighbor's fill
* factor during gap filling for minimum feature size preservation. */
vector<double> fill_factors(diagram.numsites); /* Factor to be multiplied with site polygon radius to yield target
fill level */
const jcv_site* sites = jcv_diagram_get_sites(&diagram);
int j = 0;
for (int i=0; i<diagram.numsites; i++) {
const jcv_point center = sites[i].p;
double pxd = (double)blurred.at<unsigned char>(
(int)round(center.y / height * blurred.rows),
(int)round(center.x / width * blurred.cols)) / 255.0;
fill_factors[sites[i].index] = sqrt(pxd);
}
/* Minimum gap between adjacent scaled site polygons. */
double min_gap_px = min_feature_size_px;
vector<double> adjusted_fill_factors;
adjusted_fill_factors.reserve(32); /* Vector to hold adjusted fill factors for each edge for gap filling */
/* now iterate over all voronoi cells again to generate each cell's scaled polygon halftone blob. */
for (int i=0; i<diagram.numsites; i++) {
const jcv_point center = sites[i].p;
double fill_factor_ours = fill_factors[sites[i].index];
/* Do not render halftone blobs that are too small */
if (fill_factor_ours * 0.5 * center_distance < min_gap_px)
continue;
/* Iterate over this cell's edges. For each edge, check the gap that would result between this cell's halftone
* blob and the neighboring cell's halftone blob based on their fill factors. If the gap is too small, either
* widen it by adjusting both fill factors down a bit (for this edge only!), or eliminate it by setting both
* fill factors to 1.0 (again, for this edge only!). */
adjusted_fill_factors.clear();
const jcv_graphedge* e = sites[i].edges;
while (e) {
/* half distance between both neighbors of this edge, i.e. sites[i] and its neighbor. */
/* Note that in a voronoi tesselation, this edge is always halfway between. */
double adjusted_fill_factor = fill_factor_ours;
if (e->neighbor != nullptr) { /* nullptr -> edge is on the voronoi map's border */
double rad = sqrt(pow(center.x - e->neighbor->p.x, 2) + pow(center.y - e->neighbor->p.y, 2)) / 2.0;
double fill_factor_theirs = fill_factors[e->neighbor->index];
double gap_px = (1.0 - fill_factor_ours) * rad + (1.0 - fill_factor_theirs) * rad;
if (gap_px > min_gap_px) {
/* all good. gap is wider than minimum. */
} else if (gap_px > 0.5 * min_gap_px) {
/* gap is narrower than minimum, but more than half of minimum width. */
/* force gap open, distribute adjustment evenly on left/right */
double fill_factor_adjustment = (min_gap_px - gap_px) / 2.0 / rad;
adjusted_fill_factor -= fill_factor_adjustment;
} else {
/* gap is less than half of minimum width. Force gap closed. */
adjusted_fill_factor = 1.0;
}
}
adjusted_fill_factors.push_back(adjusted_fill_factor);
e = e->next;
}
/* Now, generate the actual halftone blob polygon */
ClipperLib::Path cell_path;
double last_fill_factor = adjusted_fill_factors.back();
e = sites[i].edges;
j = 0;
while (e) {
double fill_factor = adjusted_fill_factors[j];
if (last_fill_factor != fill_factor) {
/* Fill factor was adjusted since last edge, so generate one extra point so we have a nice radial
* "step". */
double x = e->pos[0].x;
double y = e->pos[0].y;
x = center.x + (x - center.x) * fill_factor;
y = center.y + (y - center.y) * fill_factor;
cairo_user_to_device(cr, &x, &y);
cell_path.push_back({ (ClipperLib::cInt)round(x * clipper_scale), (ClipperLib::cInt)round(y * clipper_scale) });
}
/* Emit endpoint of current edge */
double x = e->pos[1].x;
double y = e->pos[1].y;
x = center.x + (x - center.x) * fill_factor;
y = center.y + (y - center.y) * fill_factor;
cairo_user_to_device(cr, &x, &y);
cell_path.push_back({ (ClipperLib::cInt)round(x * clipper_scale), (ClipperLib::cInt)round(y * clipper_scale) });
j += 1;
last_fill_factor = fill_factor;
e = e->next;
}
/* Now, clip the halftone blob generated above against the given clip path. We do this individually for each
* blob since this way is *much* faster than throwing a million blobs at once at poor clipper. */
ClipperLib::Paths polys;
ClipperLib::Clipper c;
c.AddPath(cell_path, ClipperLib::ptSubject, /* closed */ true);
if (!clip_path.empty()) {
c.AddPaths(clip_path, ClipperLib::ptClip, /* closed */ true);
}
c.StrictlySimple(true);
c.Execute(ClipperLib::ctIntersection, polys, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
/* Export halftone blob to debug svg */
cairo_save(cr);
cairo_set_matrix(cr, &viewport_matrix);
cairo_new_path(cr);
ClipperLib::cairo::clipper_to_cairo(polys, cr, CAIRO_PRECISION, ClipperLib::cairo::tNone);
cairo_set_source_rgba(cr, 1, 1, 1, 1);
cairo_fill(cr);
cairo_restore(cr);
/* And finally, export halftone blob to gerber. */
cairo_save(cr);
cairo_identity_matrix(cr);
for (const auto &poly : polys) {
/* FIXME */
//export_as_gerber(cr, poly, /* dark */ true);
}
cairo_restore(cr);
}
blurred.release();
jcv_diagram_free( &diagram );
delete grid_centers;
cairo_restore(cr);
}