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c# - .Net 与 GraphicsPath.Widen() 相反

转载 作者:IT王子 更新时间:2023-10-29 04:49:34 27 4
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我需要与 .Net 中的 GraphicsPath.Widen() 方法相反的方法:

public GraphicsPath Widen()

Widen() 方法不接受负参数,因此我需要等效于 Inset 方法:

public GraphicsPath Inset()

您可以在开源 Inkscape 应用程序 (www.Inkscape.org) 中执行此操作,方法是转到菜单并选择“路径/插入”(插入量存储在 Inkscape 属性对话框中)。由于 Inkscape 是开源的,所以应该可以在 C#.Net 中执行此操作,但我无法终生遵循 Inkscape C++ 源代码(而且我只需要这个功能,所以我不能证明学习 C++ 是合理的)来完成这个)。

基本上,我需要一个带有此签名的 GraphicsPath 扩展方法:

public static GraphicsPath Inset(this GraphicsPath original, float amount)
{
//implementation
}

如签名所述,它将采用 GraphicsPath 对象和 .Inset() 路径传递的数量……就像 Inkscape 今天所做的那样。如果它简化了任何事情,所讨论的 GraphicsPaths 都是从 .PolyBezier 方法(而不是其他任何东西)创建的,因此除非您想要,否则无需考虑矩形、椭圆或任何其他形状这样做是为了完整性。

不幸的是,我没有使用 C++ 代码的经验,所以我几乎不可能遵循 Inkscape 中包含的 C++ 逻辑。

.

[编辑:]根据要求,这是“MakeOffset”Inkscape 代码。 Inset 的第二个参数 (double dec) 将为负数,该参数的绝对值是引入形状的量。

我知道这里有很多依赖。如果您需要查看更多 Inkscape 源文件,请在此处查看:http://sourceforge.net/projects/inkscape/files/inkscape/0.48/

int
Shape::MakeOffset (Shape * a, double dec, JoinType join, double miter, bool do_profile, double cx, double cy, double radius, Geom::Matrix *i2doc)
{
Reset (0, 0);
MakeBackData(a->_has_back_data);

bool done_something = false;

if (dec == 0)
{
_pts = a->_pts;
if (numberOfPoints() > maxPt)
{
maxPt = numberOfPoints();
if (_has_points_data) {
pData.resize(maxPt);
_point_data_initialised = false;
_bbox_up_to_date = false;
}
}

_aretes = a->_aretes;
if (numberOfEdges() > maxAr)
{
maxAr = numberOfEdges();
if (_has_edges_data)
eData.resize(maxAr);
if (_has_sweep_src_data)
swsData.resize(maxAr);
if (_has_sweep_dest_data)
swdData.resize(maxAr);
if (_has_raster_data)
swrData.resize(maxAr);
if (_has_back_data)
ebData.resize(maxAr);
}
return 0;
}
if (a->numberOfPoints() <= 1 || a->numberOfEdges() <= 1 || a->type != shape_polygon)
return shape_input_err;

a->SortEdges ();

a->MakeSweepDestData (true);
a->MakeSweepSrcData (true);

for (int i = 0; i < a->numberOfEdges(); i++)
{
// int stP=a->swsData[i].stPt/*,enP=a->swsData[i].enPt*/;
int stB = -1, enB = -1;
if (dec > 0)
{
stB = a->CycleNextAt (a->getEdge(i).st, i);
enB = a->CyclePrevAt (a->getEdge(i).en, i);
}
else
{
stB = a->CyclePrevAt (a->getEdge(i).st, i);
enB = a->CycleNextAt (a->getEdge(i).en, i);
}

Geom::Point stD, seD, enD;
double stL, seL, enL;
stD = a->getEdge(stB).dx;
seD = a->getEdge(i).dx;
enD = a->getEdge(enB).dx;

stL = sqrt (dot(stD,stD));
seL = sqrt (dot(seD,seD));
enL = sqrt (dot(enD,enD));
MiscNormalize (stD);
MiscNormalize (enD);
MiscNormalize (seD);

Geom::Point ptP;
int stNo, enNo;
ptP = a->getPoint(a->getEdge(i).st).x;

double this_dec;
if (do_profile && i2doc) {
double alpha = 1;
double x = (Geom::L2(ptP * (*i2doc) - Geom::Point(cx,cy))/radius);
if (x > 1) {
this_dec = 0;
} else if (x <= 0) {
this_dec = dec;
} else {
this_dec = dec * (0.5 * cos (M_PI * (pow(x, alpha))) + 0.5);
}
} else {
this_dec = dec;
}

if (this_dec != 0)
done_something = true;

int usePathID=-1;
int usePieceID=0;
double useT=0.0;
if ( a->_has_back_data ) {
if ( a->ebData[i].pathID >= 0 && a->ebData[stB].pathID == a->ebData[i].pathID && a->ebData[stB].pieceID == a->ebData[i].pieceID
&& a->ebData[stB].tEn == a->ebData[i].tSt ) {
usePathID=a->ebData[i].pathID;
usePieceID=a->ebData[i].pieceID;
useT=a->ebData[i].tSt;
} else {
usePathID=a->ebData[i].pathID;
usePieceID=0;
useT=0;
}
}
if (dec > 0)
{
Path::DoRightJoin (this, this_dec, join, ptP, stD, seD, miter, stL, seL,
stNo, enNo,usePathID,usePieceID,useT);
a->swsData[i].stPt = enNo;
a->swsData[stB].enPt = stNo;
}
else
{
Path::DoLeftJoin (this, -this_dec, join, ptP, stD, seD, miter, stL, seL,
stNo, enNo,usePathID,usePieceID,useT);
a->swsData[i].stPt = enNo;
a->swsData[stB].enPt = stNo;
}
}

if (dec < 0)
{
for (int i = 0; i < numberOfEdges(); i++)
Inverse (i);
}

if ( _has_back_data ) {
for (int i = 0; i < a->numberOfEdges(); i++)
{
int nEd=AddEdge (a->swsData[i].stPt, a->swsData[i].enPt);
ebData[nEd]=a->ebData[i];
}
} else {
for (int i = 0; i < a->numberOfEdges(); i++)
{
AddEdge (a->swsData[i].stPt, a->swsData[i].enPt);
}
}

a->MakeSweepSrcData (false);
a->MakeSweepDestData (false);

return (done_something? 0 : shape_nothing_to_do);
}

.

[编辑]

@Simon Mourier - 了不起的工作。代码甚至干净可读!干得好,先生。不过,我确实有几个问题要问你。

首先,Amount 的正数代表什么?我在想,对于 Offset 方法,正数是“开始”,负数是“插入”,但你的例子似乎恰恰相反。

其次,我做了一些基本测试(只是扩展了你的样本),发现了一些奇怪的地方。

这是当偏移量增加时 cool 中的“l”会发生什么(对于这样一个简单的字母,它肯定会引起问题!)。

Simon Test 2

...以及重现该代码的代码:

    private void Form1_Paint(object sender, PaintEventArgs e)
{
GraphicsPath path = new GraphicsPath();

path.AddString("cool", new FontFamily("Arial"), 0, 200, new PointF(), StringFormat.GenericDefault);

GraphicsPath offset1 = path.Offset(32);

e.Graphics.DrawPath(new Pen(Color.Black, 1), path);
e.Graphics.DrawPath(new Pen(Color.Red, 1), offset1);
}

最后,有点不同。这是 Wingdings 中的“S”字符(看起来像一滴泪珠):

Tear Drop

代码如下:

    private void Form1_Paint(object sender, PaintEventArgs e)
{
GraphicsPath path = new GraphicsPath();
path.AddString("S", new FontFamily("Wingdings"), 0, 200, new PointF(), StringFormat.GenericDefault);
GraphicsPath offset1 = path.Offset(20);

e.Graphics.DrawPath(new Pen(Color.Black, 1), path);
e.Graphics.DrawPath(new Pen(Color.Red, 1), offset1);
}

老兄,这太近了,让我想哭。不过,它仍然不起作用。

我认为解决这个问题的方法是查看插入向量何时相交,并停止插入超过该点。如果 Inset 量太大(或路径太小)以至于什么都没有,则路径应该消失(变为空),而不是自行反转并重新扩展。

同样,我不会以任何方式批评您所做的事情,但我想知道您是否知道这些示例可能会发生什么。

(PS - 我添加了“this”关键字以使其成为扩展方法,因此您可能需要使用方法(参数)符号调用代码才能运行这些示例)

.

@RANRan 通过重新使用 GraphicsPath native 方法得出了类似的输出。伙计,这很难。他们俩都很亲密。

这是两个示例的屏幕截图,使用的是 Wingdings 中的字符“S”:

Tear drop comparison

@Simon 在左边,@Ran 在右边。

这是在 Inkscape 中执行“插入”后的相同泪滴“S”字符。插图很干净:

Tear Inkscape

顺便说一下,这是@Ran 测试的代码:

    private void Form1_Paint(object sender, PaintEventArgs e)
{
GraphicsPath path = new GraphicsPath();
path.AddString("S", new FontFamily("Wingdings"), 0, 200, new PointF(), StringFormat.GenericDefault);
e.Graphics.DrawPath(new Pen(Color.Black, 1), path);

GraphicsPath offset1 = path.Shrink(20);
e.Graphics.DrawPath(new Pen(Color.Red, 1), offset1);
}

最佳答案

我仍然会发布我的新解决方案,尽管它并不完美,其中包含一些需要修复的问题列表。也许您会想从中吸取一部分并改进它们,或者可能其中有一些学习值(value)。

首先是图片——我最好的嵌入泪珠符号:

alt text

我做了什么

  1. 我使用 GraphicsPath.Widen 生成给定图形的“内部”和“外部”边缘。

  2. 我扫描了生成的 GraphicsPath 的点,以移除外边缘并仅保留内边缘。

  3. 我使用 GraphicsPath.Flatten 将内边缘展平,这样图形就只包含线段(没有曲线)。

  4. 然后我扫描了内部路径上的所有点,并且对于每个当前段:

    4.1。如果当前点 p 在原始路径之外,或者太靠近原始路径上的某个线段,我会在当前边上计算一个新点,该点与原始路径,我用这个点代替 p,并将它连接到我已经扫描过的部分。

    4.2。解决方案中的当前限制:我从计算点继续,向前扫描。这意味着不能很好地支持带孔的形状(例如 Arial“o”)。要解决此问题,必须维护一个“断开连接”图形的列表,并重新连接在同一点结束(或彼此“足够接近”的末端)的图形。

问题

首先我会指出最主要的问题和限制,然后我会发布代码本身。

  1. GraphicsPath.Widen 似乎无法生成干净的形状。我得到的内部图形有小的(但大部分是看不见的)“锯齿状”。这样做的意义在于 A) 我的剔除算法会产生更多噪声,B) 图中有更多点,因此性能会下降。

  2. 目前的表现勉强可以接受,如果有的话。我的解决方案目前以一种非常简单的方式(在 O(n^n) 中)进行扫描,以找到“太靠近”内边缘候选点的线段。这导致算法非常慢。它可以通过维护一些数据结构来改进,其中段按x排序,从而大大减少距离计算的次数。

  3. 我没有费心去优化代码以使用 structs 并且还有很多其他地方可以优化代码以使其更快。

    <
  4. 不支持带孔的形状,其中内部图形必须“拆分”为多个图形(如 Arial“o”)。我知道如何实现它,但它需要更多时间:)

  5. 我会考虑采用 Simon 移动现有点以获得内部图形的方法,以及我清理该路径的方法。 (但由于 Simon 解决方案中的一个错误,我此时不能这样做,例如,导致撕裂符号的尖端移动到形状内的有效位置。我的算法认为这个位置是有效的并且不会清理它)。

代码

我无法避免想出一些我自己的数学/几何实用程序。所以这是代码...

就我个人而言,我认为这值得赏金,即使它不是一个完美的解决方案...:)

public class LineSegment
{
private readonly LineEquation line;
private RectangleF bindingRectangle;

public PointF A { get; private set; }
public PointF B { get; private set; }

public LineSegment(PointF a, PointF b)
{
A = a;
B = b;

line = new LineEquation(a, b);
bindingRectangle = new RectangleF(
Math.Min(a.X, b.X), Math.Min(a.Y, b.Y),
Math.Abs(a.X - b.X), Math.Abs(a.Y - b.Y));
}

public PointF? Intersect(LineSegment other)
{
var p = line.Intersect(other.line);
if (p == null) return null;

if (bindingRectangle.Contains(p.Value) &&
other.bindingRectangle.Contains(p.Value))
{
return p;
}
return null;
}

public float Distance(PointF p)
{
if (LineEquation.IsBetween(line.GetNormalAt(A), p, line.GetNormalAt(B)))
{
return line.Distance(p);
}
return Math.Min(Distance(A, p), Distance(B, p));

}

static float Distance(PointF p1, PointF p2)
{
var x = p1.X - p2.X;
var y = p1.Y - p2.Y;
return (float) Math.Sqrt(x*x + y*y);
}

public PointF? IntersectAtDistance(LineSegment segmentToCut, float width)
{
// always assuming other.A is the farthest end
var distance = width* (line.IsAboveOrRightOf(segmentToCut.A) ? 1 : -1);
var parallelLine = line.GetParallelLine(distance);

var p = parallelLine.Intersect(segmentToCut.line);
if (p.HasValue)
{
if (LineEquation.IsBetween(line.GetNormalAt(A), p.Value, line.GetNormalAt(B)) &&
segmentToCut.bindingRectangle.Contains(p.Value))
{
return p;
}
}

List<PointF> points = new List<PointF>();
points.AddRange(segmentToCut.line.Intersect(new CircleEquation(width, A)));
points.AddRange(segmentToCut.line.Intersect(new CircleEquation(width, B)));

return GetNearestPoint(segmentToCut.A, points);
}

public static PointF GetNearestPoint(PointF p, IEnumerable<PointF> points)
{
float minDistance = float.MaxValue;
PointF nearestPoint = p;
foreach (var point in points)
{
var d = Distance(p, point);
if (d < minDistance)
{
minDistance = d;
nearestPoint = point;
}
}
return nearestPoint;
}
}

public class LineEquation
{
private readonly float a;
private readonly float b;

private readonly bool isVertical;
private readonly float xConstForVertical;

public LineEquation(float a, float b)
{
this.a = a;
this.b = b;
isVertical = false;
}

public LineEquation(float xConstant)
{
isVertical = true;
xConstForVertical = xConstant;
}

public LineEquation(float a, PointF p)
{
this.a = a;
b = p.Y - a*p.X;
isVertical = false;
}

public LineEquation(PointF p1, PointF p2)
{
if (p1.X == p2.X)
{
isVertical = true;
xConstForVertical = p1.X;
return;
}

a = (p1.Y - p2.Y)/(p1.X - p2.X);
b = p1.Y - a * p1.X;
isVertical = false;
}

public PointF? Intersect(float x)
{
if (isVertical)
{
return null;
}
return new PointF(x, a*x + b);
}

public PointF? Intersect(LineEquation other)
{
if (isVertical && other.isVertical) return null;
if (a == other.a) return null;

if (isVertical) return other.Intersect(xConstForVertical);
if (other.isVertical) return Intersect(other.xConstForVertical);

// both have slopes and are not parallel
var x = (b - other.b) / (other.a - a);
return Intersect(x);
}

public float Distance(PointF p)
{
if (isVertical)
{
return Math.Abs(p.X - xConstForVertical);
}
var p1 = Intersect(0).Value;
var p2 = Intersect(100).Value;

var x1 = p.X - p1.X;
var y1 = p.Y - p1.Y;
var x2 = p2.X - p1.X;
var y2 = p2.Y - p1.Y;

return (float) (Math.Abs(x1*y2 - x2*y1) / Math.Sqrt(x2*x2 + y2*y2));
}

public bool IsAboveOrRightOf(PointF p)
{
return isVertical ?
xConstForVertical > p.X :
a*p.X + b > p.Y;
}

public static bool IsBetween(LineEquation l1, PointF p, LineEquation l2)
{
return l1.IsAboveOrRightOf(p) ^ l2.IsAboveOrRightOf(p);
}

public LineEquation GetParallelLine(float distance)
{
if (isVertical) return new LineEquation(xConstForVertical + distance);

var angle = Math.Atan(a);
float dy = (float) (distance/Math.Sin(angle));
return new LineEquation(a, b - dy);
}

public LineEquation GetNormalAt(PointF p)
{
if (isVertical) return new LineEquation(p.X);

var newA = -1/a;
var newB = (a + 1/a)*p.X + b;
return new LineEquation(newA, newB);
}

public PointF[] Intersect(CircleEquation circle)
{
var cx = circle.Center.X;
var cy = circle.Center.Y;
var r = circle.Radius;

if (isVertical)
{
var distance = Math.Abs(cx - xConstForVertical);
if (distance > r) return new PointF[0];
if (distance == r) return new[] {new PointF(xConstForVertical, cy) };

// two intersections
var dx = cx - xConstForVertical;

var qe = new QuadraticEquation(
1,
-2 * cy,
r * r - dx * dx);

return qe.Solve();
}

var t = b - cy;
var q = new QuadraticEquation(
1 + a*a,
2*a*t - 2*cx,
cx*cx + t*t - r*r);

var solutions = q.Solve();
for (var i = 0; i < solutions.Length; i++)
solutions[i] = Intersect(solutions[i].X).Value;
return solutions;
}
}

public class CircleEquation
{
public float Radius { get; private set; }
public PointF Center { get; private set; }

public CircleEquation(float radius, PointF center)
{
Radius = radius;
Center = center;
}
}

public class QuadraticEquation
{
public float A { get; private set; }
public float B { get; private set; }
public float C { get; private set; }

public QuadraticEquation(float a, float b, float c)
{
A = a;
B = b;
C = c;
}

public PointF Intersect(float x)
{
return new PointF(x, A*x*x + B*x + C);
}
public PointF[] Solve()
{
var d = B*B - 4*A*C;
if (d < 0) return new PointF[0];
if (d == 0)
{
var x = -B / (2*A);
return new[] { Intersect(x) };
}

var sd = Math.Sqrt(d);
var x1 = (float) ((-B - sd) / (2f*A));
var x2 = (float) ((-B + sd) / (2*A));
return new[] { Intersect(x1), Intersect(x2) };
}
}

public static class GraphicsPathExtension
{
public static GraphicsPath Shrink(this GraphicsPath originalPath, float width)
{
originalPath.CloseAllFigures();
originalPath.Flatten();
var parts = originalPath.SplitFigures();
var shrunkPaths = new List<GraphicsPath>();

foreach (var part in parts)
{
using (var widePath = new GraphicsPath(part.PathPoints, part.PathTypes))
{
// widen the figure
widePath.Widen(new Pen(Color.Black, width * 2));

// pick the inner edge
var innerEdge = widePath.SplitFigures()[1];
var fixedPath = CleanPath(innerEdge, part, width);
if (fixedPath.PointCount > 0)
shrunkPaths.Add(fixedPath);
}
}

// build the result
originalPath.Reset();
foreach (var p in shrunkPaths)
{
originalPath.AddPath(p, false);
}
return originalPath;
}

public static IList<GraphicsPath> SplitFigures(this GraphicsPath path)
{
var paths = new List<GraphicsPath>();
var position = 0;
while (position < path.PointCount)
{
var figureCount = CountNextFigure(path.PathData, position);

var points = new PointF[figureCount];
var types = new byte[figureCount];

Array.Copy(path.PathPoints, position, points, 0, figureCount);
Array.Copy(path.PathTypes, position, types, 0, figureCount);
position += figureCount;

paths.Add(new GraphicsPath(points, types));
}
return paths;
}

static int CountNextFigure(PathData data, int position)
{
var count = 0;
for (var i = position; i < data.Types.Length; i++)
{
count++;
if (0 != (data.Types[i] & (int)PathPointType.CloseSubpath))
{
return count;
}
}
return count;
}

static GraphicsPath CleanPath(GraphicsPath innerPath, GraphicsPath originalPath, float width)
{
var points = new List<PointF>();
Region originalRegion = new Region(originalPath);

// find first valid point
int firstValidPoint = 0;
IEnumerable<LineSegment> segs;

while (IsPointTooClose(
innerPath.PathPoints[firstValidPoint],
originalPath, originalRegion, width, out segs))
{
firstValidPoint++;
if (firstValidPoint == innerPath.PointCount) return new GraphicsPath();
}

var prevP = innerPath.PathPoints[firstValidPoint];
points.Add(prevP);

for (int i = 1; i < innerPath.PointCount; i++)
{
var p = innerPath.PathPoints[(firstValidPoint + i) % innerPath.PointCount];

if (!IsPointTooClose(p, originalPath, originalRegion, width, out segs))
{
prevP = p;
points.Add(p);
continue;
}

var invalidSegment = new LineSegment(prevP, p);

// found invalid point (too close or external to original figure)
IEnumerable<PointF> cutPoints =
segs.Select(seg => seg.IntersectAtDistance(invalidSegment, width).Value);
var cutPoint = LineSegment.GetNearestPoint(prevP, cutPoints);

// now add the cutPoint instead of 'p'.
points.Add(cutPoint);
prevP = cutPoint;
}

var types = new List<byte>();
for (int i = 0; i < points.Count - 1; i++)
{
types.Add(1);
}
types.Add(129);

return points.Count == 0 ?
new GraphicsPath() :
new GraphicsPath(points.ToArray(), types.ToArray());
}

static bool IsPointTooClose(
PointF p, GraphicsPath path, Region region,
float distance, out IEnumerable<LineSegment> breakingSegments)
{
if (!region.IsVisible(p))
{
breakingSegments = new LineSegment[0];
return true;
}

var segs = new List<LineSegment>();
foreach (var seg in GetSegments(path))
{
if (seg.Distance(p) < distance)
{
segs.Add(seg);
}
}
breakingSegments = segs;
return segs.Count > 0;
}

static public IEnumerable<LineSegment> GetSegments(GraphicsPath path)
{
for (var i = 0; i < path.PointCount; i++)
{
yield return
new LineSegment(path.PathPoints[i], path.PathPoints[(i + 1) % path.PointCount]);
}
}
}

关于c# - .Net 与 GraphicsPath.Widen() 相反,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/4552008/

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