117 lines
4.7 KiB
C#
117 lines
4.7 KiB
C#
#region PDFsharp - A .NET library for processing PDF
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//
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// Authors:
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// Stefan Lange
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//
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// Copyright (c) 2005-2016 empira Software GmbH, Cologne Area (Germany)
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//
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// http://www.PdfSharp.com
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// http://sourceforge.net/projects/pdfsharp
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//
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// Permission is hereby granted, free of charge, to any person obtaining a
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// copy of this software and associated documentation files (the "Software"),
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// to deal in the Software without restriction, including without limitation
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// the rights to use, copy, modify, merge, publish, distribute, sublicense,
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// and/or sell copies of the Software, and to permit persons to whom the
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// Software is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included
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// in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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#endregion
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namespace PdfSharpCore.Drawing
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{
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// In GDI+ the functions Save/Restore, BeginContainer/EndContainer, Transform, SetClip and ResetClip
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// can be combined in any order. E.g. you can set a clip region, save the graphics state, empty the
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// clip region and draw without clipping. Then you can restore to the previous clip region. With PDF
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// this behavior is hard to implement. To solve this problem I first an automaton that keeps track
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// of all clipping paths and the current transformation when the clip path was set. The automation
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// manages a PDF graphics state stack to calculate the desired bahaviour. It also takes into consideration
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// not to multiply with inverse matrixes when the user sets a new transformation matrix.
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// After the design works on pager I decided not to implement it because it is much to large-scale.
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// Instead I lay down some rules how to use the XGraphics class.
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//
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// * Before you set a transformation matrix save the graphics state (Save) or begin a new container
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// (BeginContainer).
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//
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// * Instead of resetting the transformation matrix, call Restore or EndContainer. If you reset the
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// transformation, in PDF must be multiplied with the inverse matrix. That leads to round off errors
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// because in PDF file only 3 digits are used and Acrobat internally uses fixed point numbers (until
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// versioin 6 or 7 I think).
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//
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// * When no clip path is defined, you can set or intersect a new path.
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//
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// * When a clip path is already defined, you can always intersect with a new one (wich leads in general
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// to a smaller clip region).
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//
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// * When a clip path is already defined, you can only reset it to the empty region (ResetClip) when
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// the graphics state stack is at the same position as it had when the clip path was defined. Otherwise
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// an error occurs.
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//
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// Keeping these rules leads to easy to read code and best results in PDF output.
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/// <summary>
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/// Represents the internal state of an XGraphics object.
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/// Used when the state is saved and restored.
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/// </summary>
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internal class InternalGraphicsState
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{
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public InternalGraphicsState(XGraphics gfx)
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{
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_gfx = gfx;
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}
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public InternalGraphicsState(XGraphics gfx, XGraphicsState state)
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{
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_gfx = gfx;
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State = state;
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State.InternalState = this;
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}
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public InternalGraphicsState(XGraphics gfx, XGraphicsContainer container)
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{
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_gfx = gfx;
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container.InternalState = this;
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}
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/// <summary>
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/// Gets or sets the current transformation matrix.
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/// </summary>
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public XMatrix Transform
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{
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get { return _transform; }
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set { _transform = value; }
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}
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XMatrix _transform;
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/// <summary>
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/// Called after this instanced was pushed on the internal graphics stack.
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/// </summary>
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public void Pushed()
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{
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}
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/// <summary>
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/// Called after this instanced was popped from the internal graphics stack.
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/// </summary>
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public void Popped()
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{
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Invalid = true;
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}
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public bool Invalid;
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readonly XGraphics _gfx;
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internal XGraphicsState State;
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}
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}
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