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freetype2/include/freetype/ftstroke.h

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/****************************************************************************
*
* ftstroke.h
*
* FreeType path stroker (specification).
*
* Copyright (C) 2002-2019 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: */
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