ref: 2c3e895c745fe417e501195310de973867f0d43e
dir: /include/freetype/ftstroke.h/
/****************************************************************************
*
* ftstroke.h
*
* FreeType path stroker (specification).
*
* Copyright 2002-2018 by
* David Turner, Robert Wilhelm, and Werner Lemberg.
*
* This file is part of the FreeType project, and may only be used,
* modified, and distributed under the terms of the FreeType project
* license, LICENSE.TXT. By continuing to use, modify, or distribute
* this file you indicate that you have read the license and
* understand and accept it fully.
*
*/
#ifndef FTSTROKE_H_
#define FTSTROKE_H_
#include <ft2build.h>
#include FT_OUTLINE_H
#include FT_GLYPH_H
FT_BEGIN_HEADER
/************************************************************************
*
* @section:
* glyph_stroker
*
* @title:
* Glyph Stroker
*
* @abstract:
* Generating bordered and stroked glyphs.
*
* @description:
* This component generates stroked outlines of a given vectorial
* glyph. It also allows you to retrieve the `outside' and/or the
* `inside' borders of the stroke.
*
* This can be useful to generate `bordered' glyph, i.e., glyphs
* displayed with a coloured (and anti-aliased) border around their
* shape.
*
* @order:
* FT_Stroker
*
* FT_Stroker_LineJoin
* FT_Stroker_LineCap
* FT_StrokerBorder
*
* FT_Outline_GetInsideBorder
* FT_Outline_GetOutsideBorder
*
* FT_Glyph_Stroke
* FT_Glyph_StrokeBorder
*
* FT_Stroker_New
* FT_Stroker_Set
* FT_Stroker_Rewind
* FT_Stroker_ParseOutline
* FT_Stroker_Done
*
* FT_Stroker_BeginSubPath
* FT_Stroker_EndSubPath
*
* FT_Stroker_LineTo
* FT_Stroker_ConicTo
* FT_Stroker_CubicTo
*
* FT_Stroker_GetBorderCounts
* FT_Stroker_ExportBorder
* FT_Stroker_GetCounts
* FT_Stroker_Export
*
*/
/**************************************************************
*
* @type:
* FT_Stroker
*
* @description:
* Opaque handle to a path stroker object.
*/
typedef struct FT_StrokerRec_* FT_Stroker;
/**************************************************************
*
* @enum:
* FT_Stroker_LineJoin
*
* @description:
* These values determine how two joining lines are rendered
* in a stroker.
*
* @values:
* FT_STROKER_LINEJOIN_ROUND ::
* Used to render rounded line joins. Circular arcs are used
* to join two lines smoothly.
*
* FT_STROKER_LINEJOIN_BEVEL ::
* Used to render beveled line joins. The outer corner of
* the joined lines is filled by enclosing the triangular
* region of the corner with a straight line between the
* outer corners of each stroke.
*
* FT_STROKER_LINEJOIN_MITER_FIXED ::
* Used to render mitered line joins, with fixed bevels if the
* miter limit is exceeded. The outer edges of the strokes
* for the two segments are extended until they meet at an
* angle. If the segments meet at too sharp an angle (such
* that the miter would extend from the intersection of the
* segments a distance greater than the product of the miter
* limit value and the border radius), then a bevel join (see
* above) is used instead. This prevents long spikes being
* created. FT_STROKER_LINEJOIN_MITER_FIXED generates a miter
* line join as used in PostScript and PDF.
*
* FT_STROKER_LINEJOIN_MITER_VARIABLE ::
* FT_STROKER_LINEJOIN_MITER ::
* Used to render mitered line joins, with variable bevels if
* the miter limit is exceeded. The intersection of the
* strokes is clipped at a line perpendicular to the bisector
* of the angle between the strokes, at the distance from the
* intersection of the segments equal to the product of the
* miter limit value and the border radius. This prevents
* long spikes being created.
* FT_STROKER_LINEJOIN_MITER_VARIABLE generates a mitered line
* join as used in XPS. FT_STROKER_LINEJOIN_MITER is an alias
* for FT_STROKER_LINEJOIN_MITER_VARIABLE, retained for
* backward compatibility.
*/
typedef enum FT_Stroker_LineJoin_
{
FT_STROKER_LINEJOIN_ROUND = 0,
FT_STROKER_LINEJOIN_BEVEL = 1,
FT_STROKER_LINEJOIN_MITER_VARIABLE = 2,
FT_STROKER_LINEJOIN_MITER = FT_STROKER_LINEJOIN_MITER_VARIABLE,
FT_STROKER_LINEJOIN_MITER_FIXED = 3
} FT_Stroker_LineJoin;
/**************************************************************
*
* @enum:
* FT_Stroker_LineCap
*
* @description:
* These values determine how the end of opened sub-paths are
* rendered in a stroke.
*
* @values:
* FT_STROKER_LINECAP_BUTT ::
* The end of lines is rendered as a full stop on the last
* point itself.
*
* FT_STROKER_LINECAP_ROUND ::
* The end of lines is rendered as a half-circle around the
* last point.
*
* FT_STROKER_LINECAP_SQUARE ::
* The end of lines is rendered as a square around the
* last point.
*/
typedef enum FT_Stroker_LineCap_
{
FT_STROKER_LINECAP_BUTT = 0,
FT_STROKER_LINECAP_ROUND,
FT_STROKER_LINECAP_SQUARE
} FT_Stroker_LineCap;
/**************************************************************
*
* @enum:
* FT_StrokerBorder
*
* @description:
* These values are used to select a given stroke border
* in @FT_Stroker_GetBorderCounts and @FT_Stroker_ExportBorder.
*
* @values:
* FT_STROKER_BORDER_LEFT ::
* Select the left border, relative to the drawing direction.
*
* FT_STROKER_BORDER_RIGHT ::
* Select the right border, relative to the drawing direction.
*
* @note:
* Applications are generally interested in the `inside' and `outside'
* borders. However, there is no direct mapping between these and the
* `left' and `right' ones, since this really depends on the glyph's
* drawing orientation, which varies between font formats.
*
* You can however use @FT_Outline_GetInsideBorder and
* @FT_Outline_GetOutsideBorder to get these.
*/
typedef enum FT_StrokerBorder_
{
FT_STROKER_BORDER_LEFT = 0,
FT_STROKER_BORDER_RIGHT
} FT_StrokerBorder;
/**************************************************************
*
* @function:
* FT_Outline_GetInsideBorder
*
* @description:
* Retrieve the @FT_StrokerBorder value corresponding to the
* `inside' borders of a given outline.
*
* @input:
* outline ::
* The source outline handle.
*
* @return:
* The border index. @FT_STROKER_BORDER_RIGHT for empty or invalid
* outlines.
*/
FT_EXPORT( FT_StrokerBorder )
FT_Outline_GetInsideBorder( FT_Outline* outline );
/**************************************************************
*
* @function:
* FT_Outline_GetOutsideBorder
*
* @description:
* Retrieve the @FT_StrokerBorder value corresponding to the
* `outside' borders of a given outline.
*
* @input:
* outline ::
* The source outline handle.
*
* @return:
* The border index. @FT_STROKER_BORDER_LEFT for empty or invalid
* outlines.
*/
FT_EXPORT( FT_StrokerBorder )
FT_Outline_GetOutsideBorder( FT_Outline* outline );
/**************************************************************
*
* @function:
* FT_Stroker_New
*
* @description:
* Create a new stroker object.
*
* @input:
* library ::
* FreeType library handle.
*
* @output:
* astroker ::
* A new stroker object handle. NULL in case of error.
*
* @return:
* FreeType error code. 0~means success.
*/
FT_EXPORT( FT_Error )
FT_Stroker_New( FT_Library library,
FT_Stroker *astroker );
/**************************************************************
*
* @function:
* FT_Stroker_Set
*
* @description:
* Reset a stroker object's attributes.
*
* @input:
* stroker ::
* The target stroker handle.
*
* radius ::
* The border radius.
*
* line_cap ::
* The line cap style.
*
* line_join ::
* The line join style.
*
* miter_limit ::
* The miter limit for the FT_STROKER_LINEJOIN_MITER_FIXED and
* FT_STROKER_LINEJOIN_MITER_VARIABLE line join styles,
* expressed as 16.16 fixed-point value.
*
* @note:
* The radius is expressed in the same units as the outline
* coordinates.
*
* This function calls @FT_Stroker_Rewind automatically.
*/
FT_EXPORT( void )
FT_Stroker_Set( FT_Stroker stroker,
FT_Fixed radius,
FT_Stroker_LineCap line_cap,
FT_Stroker_LineJoin line_join,
FT_Fixed miter_limit );
/**************************************************************
*
* @function:
* FT_Stroker_Rewind
*
* @description:
* Reset a stroker object without changing its attributes.
* You should call this function before beginning a new
* series of calls to @FT_Stroker_BeginSubPath or
* @FT_Stroker_EndSubPath.
*
* @input:
* stroker ::
* The target stroker handle.
*/
FT_EXPORT( void )
FT_Stroker_Rewind( FT_Stroker stroker );
/**************************************************************
*
* @function:
* FT_Stroker_ParseOutline
*
* @description:
* A convenience function used to parse a whole outline with
* the stroker. The resulting outline(s) can be retrieved
* later by functions like @FT_Stroker_GetCounts and @FT_Stroker_Export.
*
* @input:
* stroker ::
* The target stroker handle.
*
* outline ::
* The source outline.
*
* opened ::
* A boolean. If~1, the outline is treated as an open path instead
* of a closed one.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* If `opened' is~0 (the default), the outline is treated as a closed
* path, and the stroker generates two distinct `border' outlines.
*
* If `opened' is~1, the outline is processed as an open path, and the
* stroker generates a single `stroke' outline.
*
* This function calls @FT_Stroker_Rewind automatically.
*/
FT_EXPORT( FT_Error )
FT_Stroker_ParseOutline( FT_Stroker stroker,
FT_Outline* outline,
FT_Bool opened );
/**************************************************************
*
* @function:
* FT_Stroker_BeginSubPath
*
* @description:
* Start a new sub-path in the stroker.
*
* @input:
* stroker ::
* The target stroker handle.
*
* to ::
* A pointer to the start vector.
*
* open ::
* A boolean. If~1, the sub-path is treated as an open one.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* This function is useful when you need to stroke a path that is
* not stored as an @FT_Outline object.
*/
FT_EXPORT( FT_Error )
FT_Stroker_BeginSubPath( FT_Stroker stroker,
FT_Vector* to,
FT_Bool open );
/**************************************************************
*
* @function:
* FT_Stroker_EndSubPath
*
* @description:
* Close the current sub-path in the stroker.
*
* @input:
* stroker ::
* The target stroker handle.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* You should call this function after @FT_Stroker_BeginSubPath.
* If the subpath was not `opened', this function `draws' a
* single line segment to the start position when needed.
*/
FT_EXPORT( FT_Error )
FT_Stroker_EndSubPath( FT_Stroker stroker );
/**************************************************************
*
* @function:
* FT_Stroker_LineTo
*
* @description:
* `Draw' a single line segment in the stroker's current sub-path,
* from the last position.
*
* @input:
* stroker ::
* The target stroker handle.
*
* to ::
* A pointer to the destination point.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* You should call this function between @FT_Stroker_BeginSubPath and
* @FT_Stroker_EndSubPath.
*/
FT_EXPORT( FT_Error )
FT_Stroker_LineTo( FT_Stroker stroker,
FT_Vector* to );
/**************************************************************
*
* @function:
* FT_Stroker_ConicTo
*
* @description:
* `Draw' a single quadratic Bezier in the stroker's current sub-path,
* from the last position.
*
* @input:
* stroker ::
* The target stroker handle.
*
* control ::
* A pointer to a Bezier control point.
*
* to ::
* A pointer to the destination point.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* You should call this function between @FT_Stroker_BeginSubPath and
* @FT_Stroker_EndSubPath.
*/
FT_EXPORT( FT_Error )
FT_Stroker_ConicTo( FT_Stroker stroker,
FT_Vector* control,
FT_Vector* to );
/**************************************************************
*
* @function:
* FT_Stroker_CubicTo
*
* @description:
* `Draw' a single cubic Bezier in the stroker's current sub-path,
* from the last position.
*
* @input:
* stroker ::
* The target stroker handle.
*
* control1 ::
* A pointer to the first Bezier control point.
*
* control2 ::
* A pointer to second Bezier control point.
*
* to ::
* A pointer to the destination point.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* You should call this function between @FT_Stroker_BeginSubPath and
* @FT_Stroker_EndSubPath.
*/
FT_EXPORT( FT_Error )
FT_Stroker_CubicTo( FT_Stroker stroker,
FT_Vector* control1,
FT_Vector* control2,
FT_Vector* to );
/**************************************************************
*
* @function:
* FT_Stroker_GetBorderCounts
*
* @description:
* Call this function once you have finished parsing your paths
* with the stroker. It returns the number of points and
* contours necessary to export one of the `border' or `stroke'
* outlines generated by the stroker.
*
* @input:
* stroker ::
* The target stroker handle.
*
* border ::
* The border index.
*
* @output:
* anum_points ::
* The number of points.
*
* anum_contours ::
* The number of contours.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* When an outline, or a sub-path, is `closed', the stroker generates
* two independent `border' outlines, named `left' and `right'.
*
* When the outline, or a sub-path, is `opened', the stroker merges
* the `border' outlines with caps. The `left' border receives all
* points, while the `right' border becomes empty.
*
* Use the function @FT_Stroker_GetCounts instead if you want to
* retrieve the counts associated to both borders.
*/
FT_EXPORT( FT_Error )
FT_Stroker_GetBorderCounts( FT_Stroker stroker,
FT_StrokerBorder border,
FT_UInt *anum_points,
FT_UInt *anum_contours );
/**************************************************************
*
* @function:
* FT_Stroker_ExportBorder
*
* @description:
* Call this function after @FT_Stroker_GetBorderCounts to
* export the corresponding border to your own @FT_Outline
* structure.
*
* Note that this function appends the border points and
* contours to your outline, but does not try to resize its
* arrays.
*
* @input:
* stroker ::
* The target stroker handle.
*
* border ::
* The border index.
*
* outline ::
* The target outline handle.
*
* @note:
* Always call this function after @FT_Stroker_GetBorderCounts to
* get sure that there is enough room in your @FT_Outline object to
* receive all new data.
*
* When an outline, or a sub-path, is `closed', the stroker generates
* two independent `border' outlines, named `left' and `right'.
*
* When the outline, or a sub-path, is `opened', the stroker merges
* the `border' outlines with caps. The `left' border receives all
* points, while the `right' border becomes empty.
*
* Use the function @FT_Stroker_Export instead if you want to
* retrieve all borders at once.
*/
FT_EXPORT( void )
FT_Stroker_ExportBorder( FT_Stroker stroker,
FT_StrokerBorder border,
FT_Outline* outline );
/**************************************************************
*
* @function:
* FT_Stroker_GetCounts
*
* @description:
* Call this function once you have finished parsing your paths
* with the stroker. It returns the number of points and
* contours necessary to export all points/borders from the stroked
* outline/path.
*
* @input:
* stroker ::
* The target stroker handle.
*
* @output:
* anum_points ::
* The number of points.
*
* anum_contours ::
* The number of contours.
*
* @return:
* FreeType error code. 0~means success.
*/
FT_EXPORT( FT_Error )
FT_Stroker_GetCounts( FT_Stroker stroker,
FT_UInt *anum_points,
FT_UInt *anum_contours );
/**************************************************************
*
* @function:
* FT_Stroker_Export
*
* @description:
* Call this function after @FT_Stroker_GetBorderCounts to
* export all borders to your own @FT_Outline structure.
*
* Note that this function appends the border points and
* contours to your outline, but does not try to resize its
* arrays.
*
* @input:
* stroker ::
* The target stroker handle.
*
* outline ::
* The target outline handle.
*/
FT_EXPORT( void )
FT_Stroker_Export( FT_Stroker stroker,
FT_Outline* outline );
/**************************************************************
*
* @function:
* FT_Stroker_Done
*
* @description:
* Destroy a stroker object.
*
* @input:
* stroker ::
* A stroker handle. Can be NULL.
*/
FT_EXPORT( void )
FT_Stroker_Done( FT_Stroker stroker );
/**************************************************************
*
* @function:
* FT_Glyph_Stroke
*
* @description:
* Stroke a given outline glyph object with a given stroker.
*
* @inout:
* pglyph ::
* Source glyph handle on input, new glyph handle on output.
*
* @input:
* stroker ::
* A stroker handle.
*
* destroy ::
* A Boolean. If~1, the source glyph object is destroyed
* on success.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* The source glyph is untouched in case of error.
*
* Adding stroke may yield a significantly wider and taller glyph
* depending on how large of a radius was used to stroke the glyph. You
* may need to manually adjust horizontal and vertical advance amounts
* to account for this added size.
*/
FT_EXPORT( FT_Error )
FT_Glyph_Stroke( FT_Glyph *pglyph,
FT_Stroker stroker,
FT_Bool destroy );
/**************************************************************
*
* @function:
* FT_Glyph_StrokeBorder
*
* @description:
* Stroke a given outline glyph object with a given stroker, but
* only return either its inside or outside border.
*
* @inout:
* pglyph ::
* Source glyph handle on input, new glyph handle on output.
*
* @input:
* stroker ::
* A stroker handle.
*
* inside ::
* A Boolean. If~1, return the inside border, otherwise
* the outside border.
*
* destroy ::
* A Boolean. If~1, the source glyph object is destroyed
* on success.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* The source glyph is untouched in case of error.
*
* Adding stroke may yield a significantly wider and taller glyph
* depending on how large of a radius was used to stroke the glyph. You
* may need to manually adjust horizontal and vertical advance amounts
* to account for this added size.
*/
FT_EXPORT( FT_Error )
FT_Glyph_StrokeBorder( FT_Glyph *pglyph,
FT_Stroker stroker,
FT_Bool inside,
FT_Bool destroy );
/* */
FT_END_HEADER
#endif /* FTSTROKE_H_ */
/* END */
/* Local Variables: */
/* coding: utf-8 */
/* End: */