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前言

本文以vtkTextActor为起点，分享VTK中Text相关的内容，希望对各位小伙伴有所帮助！

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目录

前言

1. vtkTextActor

1.1 SetInput设置输入

1.2 设置最小、最大尺寸

1.3 设置缩放模式

1.4 设置文本对齐位置

1.5 设置文本方向

1.6 设置文字属性

1.7 获取文字包围盒

1.8 设置约束的字体大小

1.9 启用非线性缩放字体大小

1.10 坐标转化方法

1.11 计算缩放字体比例

结论：

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1. vtkTextActor

        用于展示文字的Actor，可以缩放，也可以不缩放。

         vtkTextActor可用于将文本注释放入窗口中。当TextScaleMode为NONE时，文本是固定字体，操作与vtkPolyDataMapper2D/vtkActor2D对相同。当TextScaleMode为VIEWPORT时，字体会调整大小，使其相对于呈现它的VIEWPORT保持一致的大小。当TextScaleMode为PROP时，字体会调整大小，使文本适合位置1和2坐标所定义的框。该类取代了已弃用的vtkScaledTextActor，并作为vtkTextMapper/vtkActor2D对的方便包装器。通过与此actor关联的vtkTextProperty设置文本属性/属性。其重要参数如下：

1.1 SetInput设置输入

  //@{
  /**
   * Set the text string to be displayed. "\n" is recognized
   * as a carriage return/linefeed (line separator).
   * The characters must be in the UTF-8 encoding.
   * Convenience method to the underlying mapper
   */
  void SetInput(const char* inputString);
  char* GetInput();
  //@}

1.2 设置最小、最大尺寸

  //@{
  /** 设置该Actor所占用的最小像素
   * Set/Get the minimum size in pixels for this actor.
   * Defaults to 10,10.
   * Only valid when TextScaleMode is PROP.
   */
  vtkSetVector2Macro(MinimumSize, int);
  vtkGetVector2Macro(MinimumSize, int);
  //@}

  //@{
  /**设置/获取文本行的最大高度，作为分配给它的垂直区域的百分比
   * 缩放文本actor。默认为1.0。
   * Set/Get the maximum height of a line of text as a
   * percentage of the vertical area allocated to this
   * scaled text actor. Defaults to 1.0.
   * Only valid when TextScaleMode is PROP.
   */
  vtkSetMacro(MaximumLineHeight, float);
  vtkGetMacro(MaximumLineHeight, float);
  //@}

1.3 设置缩放模式

  //@{
  /**
   * 设置文本的缩放方式。
   * 如果设置为vtkTextActor::TEXT_SCALE_MODE_NONE，字体大小将由TextProperty中给定的大小固定。
   * 如果设置为vtkTextActor::TEXT_SCALE_MODE_PROP，文本将被缩放到完全适合由位置1和2坐标指定的道具。
   * 如果设置为vtkTextActor::TEXT_SCALE_MODE_VIEWPORT，文本将根据显示的viewport的大小进行缩放。
   * Set how text should be scaled.  If set to
   * vtkTextActor::TEXT_SCALE_MODE_NONE, the font size will be fixed by the
   * size given in TextProperty.  If set to vtkTextActor::TEXT_SCALE_MODE_PROP,
   * the text will be scaled to fit exactly in the prop as specified by the
   * position 1 & 2 coordinates.  If set to
   * vtkTextActor::TEXT_SCALE_MODE_VIEWPORT, the text will be scaled based on
   * the size of the viewport it is displayed in.
   */
  vtkSetClampMacro(TextScaleMode, int, TEXT_SCALE_MODE_NONE, TEXT_SCALE_MODE_VIEWPORT);
  vtkGetMacro(TextScaleMode, int);
  void SetTextScaleModeToNone() { this->SetTextScaleMode(TEXT_SCALE_MODE_NONE); }
  void SetTextScaleModeToProp() { this->SetTextScaleMode(TEXT_SCALE_MODE_PROP); }
  void SetTextScaleModeToViewport() { this->SetTextScaleMode(TEXT_SCALE_MODE_VIEWPORT); }
  //@}

  enum
  {
    TEXT_SCALE_MODE_NONE = 0,
    TEXT_SCALE_MODE_PROP,
    TEXT_SCALE_MODE_VIEWPORT
  };

1.4 设置文本对齐位置

  //@{
  /**
   * Turn on or off the UseBorderAlign option.
   * When UseBorderAlign is on, the bounding rectangle is used to align the text,
   * which is the proper behavior when using vtkTextRepresentation
   */
  vtkSetMacro(UseBorderAlign, vtkTypeBool);
  vtkGetMacro(UseBorderAlign, vtkTypeBool);
  vtkBooleanMacro(UseBorderAlign, vtkTypeBool);
  //@}

  //@{
  /**
   * This method is being deprecated.  Use SetJustification and
   * SetVerticalJustification in text property instead.
   * Set/Get the Alignment point
   * if zero (default), the text aligns itself to the bottom left corner
   * (which is defined by the PositionCoordinate)
   * otherwise the text aligns itself to corner/midpoint or centre
   * @verbatim
   * 6   7   8
   * 3   4   5
   * 0   1   2
   * @endverbatim
   * This is the same as setting the TextProperty's justification.
   * Currently TextActor is not oriented around its AlignmentPoint.
   */
  void SetAlignmentPoint(int point);
  int GetAlignmentPoint();
  //@}

1.5 设置文本方向

  //@{
  /**
   * 围绕对齐点逆时针旋转。单位以度为单位，默认为0。
   * text属性中的方向旋转纹理图中的文本。它可能不会给你想要的效果。
   * Counterclockwise rotation around the Alignment point.
   * Units are in degrees and defaults to 0.
   * The orientation in the text property rotates the text in the
   * texture map.  It will proba ly not give you the effect you
   * desire.
   */
  void SetOrientation(float orientation);
  vtkGetMacro(Orientation, float);
  //@}

1.6 设置文字属性

  //@{
  /**
   * Set/Get the text property.
   */
  virtual void SetTextProperty(vtkTextProperty* p);
  vtkGetObjectMacro(TextProperty, vtkTextProperty);
  //@}

1.7 获取文字包围盒

  /**
   * Return the bounding box coordinates of the text in pixels.
   * The bbox array is populated with [ xmin, xmax, ymin, ymax ]
   * values in that order.
   */
  virtual void GetBoundingBox(vtkViewport* vport, double bbox[4]);

  /**
   * Syntactic sugar to get the size of text instead of the entire bounding box.
   */
  virtual void GetSize(vtkViewport* vport, double size[2]);

1.8 设置约束的字体大小

  //@{
  /**
   * 根据设置的目标矩形，计算并设置合适的字体大小。
   * 该方法的静态版本也可用于方便其他类(例如，小部件)。
   * Set and return the font size required to make this mapper fit in a given
   * target rectangle (width x height, in pixels). A static version of the
   * method is also available for convenience to other classes (e.g., widgets).
   */
  virtual int SetConstrainedFontSize(vtkViewport*, int targetWidth, int targetHeight);
  static int SetConstrainedFontSize(vtkTextActor*, vtkViewport*, int targetWidth, int targetHeight);
  //@}

  /**
   * 设置并返回使映射器数组的每个元素适合给定矩形(宽度x高度，以像素为单位)所需的字体大小。
   * 此字体大小是适合此约束中最大映射器所需的最小大小。
   * Set and return the font size required to make each element of an array
   * of mappers fit in a given rectangle (width x height, in pixels).  This
   * font size is the smallest size that was required to fit the largest
   * mapper in this constraint.
   */
  static int SetMultipleConstrainedFontSize(vtkViewport*, int targetWidth, int targetHeight,
    vtkTextActor** actors, int nbOfActors, int* maxResultingSize);

1.9 启用非线性缩放字体大小

  /**
   * 启用非线性缩放字体大小。这在与缩放文本结合使用时非常有用。
   * 对于小窗口，您希望使用整个缩放文本区域。
   * 对于较大的窗口，您需要将字体大小减小一些，以便不使用整个区域。
   * 这些值修改计算的字体大小如下:newFontSize = pow(FontSize，指数)*pow(目标，1.0 -指数)
   * 通常指 数应该在0.7左右，目标应该在10左右
   * Enable non-linear scaling of font sizes. This is useful in combination
   * with scaled text. With small windows you want to use the entire scaled
   * text area. With larger windows you want to reduce the font size some so
   * that the entire area is not used. These values modify the computed font
   * size as follows:
   * newFontSize = pow(FontSize,exponent)*pow(target,1.0 - exponent)
   * typically exponent should be around 0.7 and target should be around 10
   */
  virtual void SetNonLinearFontScale(double exponent, int target);

1.10 坐标转化方法

  /**这只是在渲染过程中使用的一种简单的坐标转换方法。
   * This is just a simple coordinate conversion method used in the render
   * process.
   */
  void SpecifiedToDisplay(double* pos, vtkViewport* vport, int specified);

  /**
   * This is just a simple coordinate conversion method used in the render
   * process.
   */
  void DisplayToSpecified(double* pos, vtkViewport* vport, int specified);

1.11 计算缩放字体比例

  /**
   * Compute the scale the font should be given the viewport.  The result
   * is placed in the ScaledTextProperty ivar.
   */
  virtual void ComputeScaledFont(vtkViewport* viewport);

  //@{
  /**
   * Get the scaled font.  Use ComputeScaledFont to set the scale for a given
   * viewport.
   */
  vtkGetObjectMacro(ScaledTextProperty, vtkTextProperty);
  //@}

  /**
   * Provide a font scaling based on a viewport.  This is the scaling factor
   * used when the TextScaleMode is set to VIEWPORT and has been made public for
   * other components to use.  This scaling assumes that the long dimension of
   * the viewport is meant to be 6 inches (a typical width of text in a paper)
   * and then resizes based on if that long dimension was 72 DPI.
   */
  static float GetFontScale(vtkViewport* viewport);

结论：

感谢各位小伙伴的点赞+关注，小易会继续努力分享，一起进步！

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