ref: f999375a9a834666f82928f9ad6293d9b25213a5
dir: /include/freetype/ftimage.h/
/****************************************************************************
*
* ftimage.h
*
* FreeType glyph image formats and default raster interface
* (specification).
*
* Copyright 1996-2018 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.
*
*/
/**************************************************************************
*
* Note: A `raster' is simply a scan-line converter, used to render
* FT_Outlines into FT_Bitmaps.
*
*/
#ifndef FTIMAGE_H_
#define FTIMAGE_H_
/* STANDALONE_ is from ftgrays.c */
#ifndef STANDALONE_
#include <ft2build.h>
#endif
FT_BEGIN_HEADER
/**************************************************************************
*
* @Section:
* basic_types
*
*/
/**************************************************************************
*
* @Type:
* FT_Pos
*
* @Description:
* The type FT_Pos is used to store vectorial coordinates. Depending
* on the context, these can represent distances in integer font
* units, or 16.16, or 26.6 fixed-point pixel coordinates.
*/
typedef signed long FT_Pos;
/**************************************************************************
*
* @Struct:
* FT_Vector
*
* @Description:
* A simple structure used to store a 2D vector; coordinates are of
* the FT_Pos type.
*
* @Fields:
* x ::
* The horizontal coordinate.
* y ::
* The vertical coordinate.
*/
typedef struct FT_Vector_
{
FT_Pos x;
FT_Pos y;
} FT_Vector;
/**************************************************************************
*
* @Struct:
* FT_BBox
*
* @Description:
* A structure used to hold an outline's bounding box, i.e., the
* coordinates of its extrema in the horizontal and vertical
* directions.
*
* @Fields:
* xMin ::
* The horizontal minimum (left-most).
*
* yMin ::
* The vertical minimum (bottom-most).
*
* xMax ::
* The horizontal maximum (right-most).
*
* yMax ::
* The vertical maximum (top-most).
*
* @Note:
* The bounding box is specified with the coordinates of the lower
* left and the upper right corner. In PostScript, those values are
* often called (llx,lly) and (urx,ury), respectively.
*
* If `yMin' is negative, this value gives the glyph's descender.
* Otherwise, the glyph doesn't descend below the baseline.
* Similarly, if `ymax' is positive, this value gives the glyph's
* ascender.
*
* `xMin' gives the horizontal distance from the glyph's origin to
* the left edge of the glyph's bounding box. If `xMin' is negative,
* the glyph extends to the left of the origin.
*/
typedef struct FT_BBox_
{
FT_Pos xMin, yMin;
FT_Pos xMax, yMax;
} FT_BBox;
/**************************************************************************
*
* @Enum:
* FT_Pixel_Mode
*
* @Description:
* An enumeration type used to describe the format of pixels in a
* given bitmap. Note that additional formats may be added in the
* future.
*
* @Values:
* FT_PIXEL_MODE_NONE ::
* Value~0 is reserved.
*
* FT_PIXEL_MODE_MONO ::
* A monochrome bitmap, using 1~bit per pixel. Note that pixels
* are stored in most-significant order (MSB), which means that
* the left-most pixel in a byte has value 128.
*
* FT_PIXEL_MODE_GRAY ::
* An 8-bit bitmap, generally used to represent anti-aliased glyph
* images. Each pixel is stored in one byte. Note that the number
* of `gray' levels is stored in the `num_grays' field of the
* @FT_Bitmap structure (it generally is 256).
*
* FT_PIXEL_MODE_GRAY2 ::
* A 2-bit per pixel bitmap, used to represent embedded
* anti-aliased bitmaps in font files according to the OpenType
* specification. We haven't found a single font using this
* format, however.
*
* FT_PIXEL_MODE_GRAY4 ::
* A 4-bit per pixel bitmap, representing embedded anti-aliased
* bitmaps in font files according to the OpenType specification.
* We haven't found a single font using this format, however.
*
* FT_PIXEL_MODE_LCD ::
* An 8-bit bitmap, representing RGB or BGR decimated glyph images
* used for display on LCD displays; the bitmap is three times
* wider than the original glyph image. See also
* @FT_RENDER_MODE_LCD.
*
* FT_PIXEL_MODE_LCD_V ::
* An 8-bit bitmap, representing RGB or BGR decimated glyph images
* used for display on rotated LCD displays; the bitmap is three
* times taller than the original glyph image. See also
* @FT_RENDER_MODE_LCD_V.
*
* FT_PIXEL_MODE_BGRA ::
* [Since 2.5] An image with four 8-bit channels per pixel,
* representing a color image (such as emoticons) with alpha
* channel. For each pixel, the format is BGRA, which means, the
* blue channel comes first in memory. The color channels are
* pre-multiplied and in the sRGB colorspace. For example, full
* red at half-translucent opacity will be represented as
* `00,00,80,80', not `00,00,FF,80'. See also @FT_LOAD_COLOR.
*/
typedef enum FT_Pixel_Mode_
{
FT_PIXEL_MODE_NONE = 0,
FT_PIXEL_MODE_MONO,
FT_PIXEL_MODE_GRAY,
FT_PIXEL_MODE_GRAY2,
FT_PIXEL_MODE_GRAY4,
FT_PIXEL_MODE_LCD,
FT_PIXEL_MODE_LCD_V,
FT_PIXEL_MODE_BGRA,
FT_PIXEL_MODE_MAX /* do not remove */
} FT_Pixel_Mode;
/* these constants are deprecated; use the corresponding `FT_Pixel_Mode' */
/* values instead. */
#define ft_pixel_mode_none FT_PIXEL_MODE_NONE
#define ft_pixel_mode_mono FT_PIXEL_MODE_MONO
#define ft_pixel_mode_grays FT_PIXEL_MODE_GRAY
#define ft_pixel_mode_pal2 FT_PIXEL_MODE_GRAY2
#define ft_pixel_mode_pal4 FT_PIXEL_MODE_GRAY4
/**************************************************************************
*
* @Struct:
* FT_Bitmap
*
* @Description:
* A structure used to describe a bitmap or pixmap to the raster.
* Note that we now manage pixmaps of various depths through the
* `pixel_mode' field.
*
* @Fields:
* rows ::
* The number of bitmap rows.
*
* width ::
* The number of pixels in bitmap row.
*
* pitch ::
* The pitch's absolute value is the number of bytes
* taken by one bitmap row, including padding.
* However, the pitch is positive when the bitmap has
* a `down' flow, and negative when it has an `up'
* flow. In all cases, the pitch is an offset to add
* to a bitmap pointer in order to go down one row.
*
* Note that `padding' means the alignment of a
* bitmap to a byte border, and FreeType functions
* normally align to the smallest possible integer
* value.
*
* For the B/W rasterizer, `pitch' is always an even
* number.
*
* To change the pitch of a bitmap (say, to make it a
* multiple of 4), use @FT_Bitmap_Convert.
* Alternatively, you might use callback functions to
* directly render to the application's surface; see
* the file `example2.cpp' in the tutorial for a
* demonstration.
*
* buffer ::
* A typeless pointer to the bitmap buffer. This
* value should be aligned on 32-bit boundaries in
* most cases.
*
* num_grays ::
* This field is only used with
* @FT_PIXEL_MODE_GRAY; it gives the number of gray
* levels used in the bitmap.
*
* pixel_mode ::
* The pixel mode, i.e., how pixel bits are stored.
* See @FT_Pixel_Mode for possible values.
*
* palette_mode ::
* This field is intended for paletted pixel modes;
* it indicates how the palette is stored. Not
* used currently.
*
* palette ::
* A typeless pointer to the bitmap palette; this
* field is intended for paletted pixel modes. Not
* used currently.
*/
typedef struct FT_Bitmap_
{
unsigned int rows;
unsigned int width;
int pitch;
unsigned char* buffer;
unsigned short num_grays;
unsigned char pixel_mode;
unsigned char palette_mode;
void* palette;
} FT_Bitmap;
/**************************************************************************
*
* @Section:
* outline_processing
*
*/
/**************************************************************************
*
* @Struct:
* FT_Outline
*
* @Description:
* This structure is used to describe an outline to the scan-line
* converter.
*
* @Fields:
* n_contours ::
* The number of contours in the outline.
*
* n_points ::
* The number of points in the outline.
*
* points ::
* A pointer to an array of `n_points' @FT_Vector
* elements, giving the outline's point coordinates.
*
* tags ::
* A pointer to an array of `n_points' chars, giving
* each outline point's type.
*
* If bit~0 is unset, the point is `off' the curve,
* i.e., a Bezier control point, while it is `on' if
* set.
*
* Bit~1 is meaningful for `off' points only. If set,
* it indicates a third-order Bezier arc control point;
* and a second-order control point if unset.
*
* If bit~2 is set, bits 5-7 contain the drop-out mode
* (as defined in the OpenType specification; the value
* is the same as the argument to the SCANMODE
* instruction).
*
* Bits 3 and~4 are reserved for internal purposes.
*
* contours ::
* An array of `n_contours' shorts, giving the end
* point of each contour within the outline. For
* example, the first contour is defined by the points
* `0' to `contours[0]', the second one is defined by
* the points `contours[0]+1' to `contours[1]', etc.
*
* flags ::
* A set of bit flags used to characterize the outline
* and give hints to the scan-converter and hinter on
* how to convert/grid-fit it. See @FT_OUTLINE_XXX.
*
* @Note:
* The B/W rasterizer only checks bit~2 in the `tags' array for the
* first point of each contour. The drop-out mode as given with
* @FT_OUTLINE_IGNORE_DROPOUTS, @FT_OUTLINE_SMART_DROPOUTS, and
* @FT_OUTLINE_INCLUDE_STUBS in `flags' is then overridden.
*/
typedef struct FT_Outline_
{
short n_contours; /* number of contours in glyph */
short n_points; /* number of points in the glyph */
FT_Vector* points; /* the outline's points */
char* tags; /* the points flags */
short* contours; /* the contour end points */
int flags; /* outline masks */
} FT_Outline;
/* */
/* Following limits must be consistent with */
/* FT_Outline.{n_contours,n_points} */
#define FT_OUTLINE_CONTOURS_MAX SHRT_MAX
#define FT_OUTLINE_POINTS_MAX SHRT_MAX
/**************************************************************************
*
* @Enum:
* FT_OUTLINE_XXX
*
* @Description:
* A list of bit-field constants use for the flags in an outline's
* `flags' field.
*
* @Values:
* FT_OUTLINE_NONE ::
* Value~0 is reserved.
*
* FT_OUTLINE_OWNER ::
* If set, this flag indicates that the outline's field arrays
* (i.e., `points', `flags', and `contours') are `owned' by the
* outline object, and should thus be freed when it is destroyed.
*
* FT_OUTLINE_EVEN_ODD_FILL ::
* By default, outlines are filled using the non-zero winding rule.
* If set to 1, the outline will be filled using the even-odd fill
* rule (only works with the smooth rasterizer).
*
* FT_OUTLINE_REVERSE_FILL ::
* By default, outside contours of an outline are oriented in
* clock-wise direction, as defined in the TrueType specification.
* This flag is set if the outline uses the opposite direction
* (typically for Type~1 fonts). This flag is ignored by the scan
* converter.
*
* FT_OUTLINE_IGNORE_DROPOUTS ::
* By default, the scan converter will try to detect drop-outs in
* an outline and correct the glyph bitmap to ensure consistent
* shape continuity. If set, this flag hints the scan-line
* converter to ignore such cases. See below for more information.
*
* FT_OUTLINE_SMART_DROPOUTS ::
* Select smart dropout control. If unset, use simple dropout
* control. Ignored if @FT_OUTLINE_IGNORE_DROPOUTS is set. See
* below for more information.
*
* FT_OUTLINE_INCLUDE_STUBS ::
* If set, turn pixels on for `stubs', otherwise exclude them.
* Ignored if @FT_OUTLINE_IGNORE_DROPOUTS is set. See below for
* more information.
*
* FT_OUTLINE_HIGH_PRECISION ::
* This flag indicates that the scan-line converter should try to
* convert this outline to bitmaps with the highest possible
* quality. It is typically set for small character sizes. Note
* that this is only a hint that might be completely ignored by a
* given scan-converter.
*
* FT_OUTLINE_SINGLE_PASS ::
* This flag is set to force a given scan-converter to only use a
* single pass over the outline to render a bitmap glyph image.
* Normally, it is set for very large character sizes. It is only
* a hint that might be completely ignored by a given
* scan-converter.
*
* @Note:
* The flags @FT_OUTLINE_IGNORE_DROPOUTS, @FT_OUTLINE_SMART_DROPOUTS,
* and @FT_OUTLINE_INCLUDE_STUBS are ignored by the smooth
* rasterizer.
*
* There exists a second mechanism to pass the drop-out mode to the
* B/W rasterizer; see the `tags' field in @FT_Outline.
*
* Please refer to the description of the `SCANTYPE' instruction in
* the OpenType specification (in file `ttinst1.doc') how simple
* drop-outs, smart drop-outs, and stubs are defined.
*/
#define FT_OUTLINE_NONE 0x0
#define FT_OUTLINE_OWNER 0x1
#define FT_OUTLINE_EVEN_ODD_FILL 0x2
#define FT_OUTLINE_REVERSE_FILL 0x4
#define FT_OUTLINE_IGNORE_DROPOUTS 0x8
#define FT_OUTLINE_SMART_DROPOUTS 0x10
#define FT_OUTLINE_INCLUDE_STUBS 0x20
#define FT_OUTLINE_HIGH_PRECISION 0x100
#define FT_OUTLINE_SINGLE_PASS 0x200
/* these constants are deprecated; use the corresponding */
/* `FT_OUTLINE_XXX' values instead */
#define ft_outline_none FT_OUTLINE_NONE
#define ft_outline_owner FT_OUTLINE_OWNER
#define ft_outline_even_odd_fill FT_OUTLINE_EVEN_ODD_FILL
#define ft_outline_reverse_fill FT_OUTLINE_REVERSE_FILL
#define ft_outline_ignore_dropouts FT_OUTLINE_IGNORE_DROPOUTS
#define ft_outline_high_precision FT_OUTLINE_HIGH_PRECISION
#define ft_outline_single_pass FT_OUTLINE_SINGLE_PASS
/* */
#define FT_CURVE_TAG( flag ) ( flag & 3 )
#define FT_CURVE_TAG_ON 1
#define FT_CURVE_TAG_CONIC 0
#define FT_CURVE_TAG_CUBIC 2
#define FT_CURVE_TAG_HAS_SCANMODE 4
#define FT_CURVE_TAG_TOUCH_X 8 /* reserved for the TrueType hinter */
#define FT_CURVE_TAG_TOUCH_Y 16 /* reserved for the TrueType hinter */
#define FT_CURVE_TAG_TOUCH_BOTH ( FT_CURVE_TAG_TOUCH_X | \
FT_CURVE_TAG_TOUCH_Y )
#define FT_Curve_Tag_On FT_CURVE_TAG_ON
#define FT_Curve_Tag_Conic FT_CURVE_TAG_CONIC
#define FT_Curve_Tag_Cubic FT_CURVE_TAG_CUBIC
#define FT_Curve_Tag_Touch_X FT_CURVE_TAG_TOUCH_X
#define FT_Curve_Tag_Touch_Y FT_CURVE_TAG_TOUCH_Y
/**************************************************************************
*
* @FuncType:
* FT_Outline_MoveToFunc
*
* @Description:
* A function pointer type used to describe the signature of a `move
* to' function during outline walking/decomposition.
*
* A `move to' is emitted to start a new contour in an outline.
*
* @Input:
* to ::
* A pointer to the target point of the `move to'.
*
* user ::
* A typeless pointer, which is passed from the caller of the
* decomposition function.
*
* @Return:
* Error code. 0~means success.
*/
typedef int
(*FT_Outline_MoveToFunc)( const FT_Vector* to,
void* user );
#define FT_Outline_MoveTo_Func FT_Outline_MoveToFunc
/**************************************************************************
*
* @FuncType:
* FT_Outline_LineToFunc
*
* @Description:
* A function pointer type used to describe the signature of a `line
* to' function during outline walking/decomposition.
*
* A `line to' is emitted to indicate a segment in the outline.
*
* @Input:
* to ::
* A pointer to the target point of the `line to'.
*
* user ::
* A typeless pointer, which is passed from the caller of the
* decomposition function.
*
* @Return:
* Error code. 0~means success.
*/
typedef int
(*FT_Outline_LineToFunc)( const FT_Vector* to,
void* user );
#define FT_Outline_LineTo_Func FT_Outline_LineToFunc
/**************************************************************************
*
* @FuncType:
* FT_Outline_ConicToFunc
*
* @Description:
* A function pointer type used to describe the signature of a `conic
* to' function during outline walking or decomposition.
*
* A `conic to' is emitted to indicate a second-order Bezier arc in
* the outline.
*
* @Input:
* control ::
* An intermediate control point between the last position
* and the new target in `to'.
*
* to ::
* A pointer to the target end point of the conic arc.
*
* user ::
* A typeless pointer, which is passed from the caller of
* the decomposition function.
*
* @Return:
* Error code. 0~means success.
*/
typedef int
(*FT_Outline_ConicToFunc)( const FT_Vector* control,
const FT_Vector* to,
void* user );
#define FT_Outline_ConicTo_Func FT_Outline_ConicToFunc
/**************************************************************************
*
* @FuncType:
* FT_Outline_CubicToFunc
*
* @Description:
* A function pointer type used to describe the signature of a `cubic
* to' function during outline walking or decomposition.
*
* A `cubic to' is emitted to indicate a third-order Bezier arc.
*
* @Input:
* control1 ::
* A pointer to the first Bezier control point.
*
* control2 ::
* A pointer to the second Bezier control point.
*
* to ::
* A pointer to the target end point.
*
* user ::
* A typeless pointer, which is passed from the caller of
* the decomposition function.
*
* @Return:
* Error code. 0~means success.
*/
typedef int
(*FT_Outline_CubicToFunc)( const FT_Vector* control1,
const FT_Vector* control2,
const FT_Vector* to,
void* user );
#define FT_Outline_CubicTo_Func FT_Outline_CubicToFunc
/**************************************************************************
*
* @Struct:
* FT_Outline_Funcs
*
* @Description:
* A structure to hold various function pointers used during outline
* decomposition in order to emit segments, conic, and cubic Beziers.
*
* @Fields:
* move_to ::
* The `move to' emitter.
*
* line_to ::
* The segment emitter.
*
* conic_to ::
* The second-order Bezier arc emitter.
*
* cubic_to ::
* The third-order Bezier arc emitter.
*
* shift ::
* The shift that is applied to coordinates before they
* are sent to the emitter.
*
* delta ::
* The delta that is applied to coordinates before they
* are sent to the emitter, but after the shift.
*
* @Note:
* The point coordinates sent to the emitters are the transformed
* version of the original coordinates (this is important for high
* accuracy during scan-conversion). The transformation is simple:
*
* {
* x' = (x << shift) - delta
* y' = (y << shift) - delta
* }
*
* Set the values of `shift' and `delta' to~0 to get the original
* point coordinates.
*/
typedef struct FT_Outline_Funcs_
{
FT_Outline_MoveToFunc move_to;
FT_Outline_LineToFunc line_to;
FT_Outline_ConicToFunc conic_to;
FT_Outline_CubicToFunc cubic_to;
int shift;
FT_Pos delta;
} FT_Outline_Funcs;
/**************************************************************************
*
* @Section:
* basic_types
*
*/
/**************************************************************************
*
* @Macro:
* FT_IMAGE_TAG
*
* @Description:
* This macro converts four-letter tags to an unsigned long type.
*
* @Note:
* Since many 16-bit compilers don't like 32-bit enumerations, you
* should redefine this macro in case of problems to something like
* this:
*
* {
* #define FT_IMAGE_TAG( value, _x1, _x2, _x3, _x4 ) value
* }
*
* to get a simple enumeration without assigning special numbers.
*/
#ifndef FT_IMAGE_TAG
#define FT_IMAGE_TAG( value, _x1, _x2, _x3, _x4 ) \
value = ( ( (unsigned long)_x1 << 24 ) | \
( (unsigned long)_x2 << 16 ) | \
( (unsigned long)_x3 << 8 ) | \
(unsigned long)_x4 )
#endif /* FT_IMAGE_TAG */
/**************************************************************************
*
* @Enum:
* FT_Glyph_Format
*
* @Description:
* An enumeration type used to describe the format of a given glyph
* image. Note that this version of FreeType only supports two image
* formats, even though future font drivers will be able to register
* their own format.
*
* @Values:
* FT_GLYPH_FORMAT_NONE ::
* The value~0 is reserved.
*
* FT_GLYPH_FORMAT_COMPOSITE ::
* The glyph image is a composite of several other images. This
* format is _only_ used with @FT_LOAD_NO_RECURSE, and is used to
* report compound glyphs (like accented characters).
*
* FT_GLYPH_FORMAT_BITMAP ::
* The glyph image is a bitmap, and can be described as an
* @FT_Bitmap. You generally need to access the `bitmap' field of
* the @FT_GlyphSlotRec structure to read it.
*
* FT_GLYPH_FORMAT_OUTLINE ::
* The glyph image is a vectorial outline made of line segments
* and Bezier arcs; it can be described as an @FT_Outline; you
* generally want to access the `outline' field of the
* @FT_GlyphSlotRec structure to read it.
*
* FT_GLYPH_FORMAT_PLOTTER ::
* The glyph image is a vectorial path with no inside and outside
* contours. Some Type~1 fonts, like those in the Hershey family,
* contain glyphs in this format. These are described as
* @FT_Outline, but FreeType isn't currently capable of rendering
* them correctly.
*/
typedef enum FT_Glyph_Format_
{
FT_IMAGE_TAG( FT_GLYPH_FORMAT_NONE, 0, 0, 0, 0 ),
FT_IMAGE_TAG( FT_GLYPH_FORMAT_COMPOSITE, 'c', 'o', 'm', 'p' ),
FT_IMAGE_TAG( FT_GLYPH_FORMAT_BITMAP, 'b', 'i', 't', 's' ),
FT_IMAGE_TAG( FT_GLYPH_FORMAT_OUTLINE, 'o', 'u', 't', 'l' ),
FT_IMAGE_TAG( FT_GLYPH_FORMAT_PLOTTER, 'p', 'l', 'o', 't' )
} FT_Glyph_Format;
/* these constants are deprecated; use the corresponding */
/* `FT_Glyph_Format' values instead. */
#define ft_glyph_format_none FT_GLYPH_FORMAT_NONE
#define ft_glyph_format_composite FT_GLYPH_FORMAT_COMPOSITE
#define ft_glyph_format_bitmap FT_GLYPH_FORMAT_BITMAP
#define ft_glyph_format_outline FT_GLYPH_FORMAT_OUTLINE
#define ft_glyph_format_plotter FT_GLYPH_FORMAT_PLOTTER
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/***** *****/
/***** R A S T E R D E F I N I T I O N S *****/
/***** *****/
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/**************************************************************************
*
* A raster is a scan converter, in charge of rendering an outline into
* a bitmap. This section contains the public API for rasters.
*
* Note that in FreeType 2, all rasters are now encapsulated within
* specific modules called `renderers'. See `ftrender.h' for more
* details on renderers.
*
*/
/**************************************************************************
*
* @Section:
* raster
*
* @Title:
* Scanline Converter
*
* @Abstract:
* How vectorial outlines are converted into bitmaps and pixmaps.
*
* @Description:
* This section contains technical definitions.
*
* @Order:
* FT_Raster
* FT_Span
* FT_SpanFunc
*
* FT_Raster_Params
* FT_RASTER_FLAG_XXX
*
* FT_Raster_NewFunc
* FT_Raster_DoneFunc
* FT_Raster_ResetFunc
* FT_Raster_SetModeFunc
* FT_Raster_RenderFunc
* FT_Raster_Funcs
*
*/
/**************************************************************************
*
* @Type:
* FT_Raster
*
* @Description:
* An opaque handle (pointer) to a raster object. Each object can be
* used independently to convert an outline into a bitmap or pixmap.
*/
typedef struct FT_RasterRec_* FT_Raster;
/**************************************************************************
*
* @Struct:
* FT_Span
*
* @Description:
* A structure used to model a single span of gray pixels when
* rendering an anti-aliased bitmap.
*
* @Fields:
* x ::
* The span's horizontal start position.
*
* len ::
* The span's length in pixels.
*
* coverage ::
* The span color/coverage, ranging from 0 (background)
* to 255 (foreground).
*
* @Note:
* This structure is used by the span drawing callback type named
* @FT_SpanFunc that takes the y~coordinate of the span as a
* parameter.
*
* The coverage value is always between 0 and 255. If you want less
* gray values, the callback function has to reduce them.
*/
typedef struct FT_Span_
{
short x;
unsigned short len;
unsigned char coverage;
} FT_Span;
/**************************************************************************
*
* @FuncType:
* FT_SpanFunc
*
* @Description:
* A function used as a call-back by the anti-aliased renderer in
* order to let client applications draw themselves the gray pixel
* spans on each scan line.
*
* @Input:
* y ::
* The scanline's y~coordinate.
*
* count ::
* The number of spans to draw on this scanline.
*
* spans ::
* A table of `count' spans to draw on the scanline.
*
* user ::
* User-supplied data that is passed to the callback.
*
* @Note:
* This callback allows client applications to directly render the
* gray spans of the anti-aliased bitmap to any kind of surfaces.
*
* This can be used to write anti-aliased outlines directly to a
* given background bitmap, and even perform translucency.
*/
typedef void
(*FT_SpanFunc)( int y,
int count,
const FT_Span* spans,
void* user );
#define FT_Raster_Span_Func FT_SpanFunc
/**************************************************************************
*
* @FuncType:
* FT_Raster_BitTest_Func
*
* @Description:
* Deprecated, unimplemented.
*/
typedef int
(*FT_Raster_BitTest_Func)( int y,
int x,
void* user );
/**************************************************************************
*
* @FuncType:
* FT_Raster_BitSet_Func
*
* @Description:
* Deprecated, unimplemented.
*/
typedef void
(*FT_Raster_BitSet_Func)( int y,
int x,
void* user );
/**************************************************************************
*
* @Enum:
* FT_RASTER_FLAG_XXX
*
* @Description:
* A list of bit flag constants as used in the `flags' field of a
* @FT_Raster_Params structure.
*
* @Values:
* FT_RASTER_FLAG_DEFAULT ::
* This value is 0.
*
* FT_RASTER_FLAG_AA ::
* This flag is set to indicate that an
* anti-aliased glyph image should be
* generated. Otherwise, it will be
* monochrome (1-bit).
*
* FT_RASTER_FLAG_DIRECT ::
* This flag is set to indicate direct
* rendering. In this mode, client
* applications must provide their own span
* callback. This lets them directly
* draw or compose over an existing bitmap.
* If this bit is not set, the target
* pixmap's buffer _must_ be zeroed before
* rendering.
*
* Direct rendering is only possible with
* anti-aliased glyphs.
*
* FT_RASTER_FLAG_CLIP ::
* This flag is only used in direct
* rendering mode. If set, the output will
* be clipped to a box specified in the
* `clip_box' field of the
* @FT_Raster_Params structure.
*
* Note that by default, the glyph bitmap
* is clipped to the target pixmap, except
* in direct rendering mode where all spans
* are generated if no clipping box is set.
*/
#define FT_RASTER_FLAG_DEFAULT 0x0
#define FT_RASTER_FLAG_AA 0x1
#define FT_RASTER_FLAG_DIRECT 0x2
#define FT_RASTER_FLAG_CLIP 0x4
/* these constants are deprecated; use the corresponding */
/* `FT_RASTER_FLAG_XXX' values instead */
#define ft_raster_flag_default FT_RASTER_FLAG_DEFAULT
#define ft_raster_flag_aa FT_RASTER_FLAG_AA
#define ft_raster_flag_direct FT_RASTER_FLAG_DIRECT
#define ft_raster_flag_clip FT_RASTER_FLAG_CLIP
/**************************************************************************
*
* @Struct:
* FT_Raster_Params
*
* @Description:
* A structure to hold the arguments used by a raster's render
* function.
*
* @Fields:
* target ::
* The target bitmap.
*
* source ::
* A pointer to the source glyph image (e.g., an
* @FT_Outline).
*
* flags ::
* The rendering flags.
*
* gray_spans ::
* The gray span drawing callback.
*
* black_spans ::
* Unused.
*
* bit_test ::
* Unused.
*
* bit_set ::
* Unused.
*
* user ::
* User-supplied data that is passed to each drawing
* callback.
*
* clip_box ::
* An optional clipping box. It is only used in
* direct rendering mode. Note that coordinates here
* should be expressed in _integer_ pixels (and not in
* 26.6 fixed-point units).
*
* @Note:
* An anti-aliased glyph bitmap is drawn if the @FT_RASTER_FLAG_AA
* bit flag is set in the `flags' field, otherwise a monochrome
* bitmap is generated.
*
* If the @FT_RASTER_FLAG_DIRECT bit flag is set in `flags', the
* raster will call the `gray_spans' callback to draw gray pixel
* spans. This allows direct composition over a pre-existing bitmap
* through user-provided callbacks to perform the span drawing and
* composition. Not supported by the monochrome rasterizer.
*/
typedef struct FT_Raster_Params_
{
const FT_Bitmap* target;
const void* source;
int flags;
FT_SpanFunc gray_spans;
FT_SpanFunc black_spans; /* unused */
FT_Raster_BitTest_Func bit_test; /* unused */
FT_Raster_BitSet_Func bit_set; /* unused */
void* user;
FT_BBox clip_box;
} FT_Raster_Params;
/**************************************************************************
*
* @FuncType:
* FT_Raster_NewFunc
*
* @Description:
* A function used to create a new raster object.
*
* @Input:
* memory ::
* A handle to the memory allocator.
*
* @Output:
* raster ::
* A handle to the new raster object.
*
* @Return:
* Error code. 0~means success.
*
* @Note:
* The `memory' parameter is a typeless pointer in order to avoid
* un-wanted dependencies on the rest of the FreeType code. In
* practice, it is an @FT_Memory object, i.e., a handle to the
* standard FreeType memory allocator. However, this field can be
* completely ignored by a given raster implementation.
*/
typedef int
(*FT_Raster_NewFunc)( void* memory,
FT_Raster* raster );
#define FT_Raster_New_Func FT_Raster_NewFunc
/**************************************************************************
*
* @FuncType:
* FT_Raster_DoneFunc
*
* @Description:
* A function used to destroy a given raster object.
*
* @Input:
* raster ::
* A handle to the raster object.
*/
typedef void
(*FT_Raster_DoneFunc)( FT_Raster raster );
#define FT_Raster_Done_Func FT_Raster_DoneFunc
/**************************************************************************
*
* @FuncType:
* FT_Raster_ResetFunc
*
* @Description:
* FreeType used to provide an area of memory called the `render
* pool' available to all registered rasterizers. This was not
* thread safe, however, and now FreeType never allocates this pool.
*
* This function is called after a new raster object is created.
*
* @Input:
* raster ::
* A handle to the new raster object.
*
* pool_base ::
* Previously, the address in memory of the render pool.
* Set this to NULL.
*
* pool_size ::
* Previously, the size in bytes of the render pool.
* Set this to 0.
*
* @Note:
* Rasterizers should rely on dynamic or stack allocation if they
* want to (a handle to the memory allocator is passed to the
* rasterizer constructor).
*/
typedef void
(*FT_Raster_ResetFunc)( FT_Raster raster,
unsigned char* pool_base,
unsigned long pool_size );
#define FT_Raster_Reset_Func FT_Raster_ResetFunc
/**************************************************************************
*
* @FuncType:
* FT_Raster_SetModeFunc
*
* @Description:
* This function is a generic facility to change modes or attributes
* in a given raster. This can be used for debugging purposes, or
* simply to allow implementation-specific `features' in a given
* raster module.
*
* @Input:
* raster ::
* A handle to the new raster object.
*
* mode ::
* A 4-byte tag used to name the mode or property.
*
* args ::
* A pointer to the new mode/property to use.
*/
typedef int
(*FT_Raster_SetModeFunc)( FT_Raster raster,
unsigned long mode,
void* args );
#define FT_Raster_Set_Mode_Func FT_Raster_SetModeFunc
/**************************************************************************
*
* @FuncType:
* FT_Raster_RenderFunc
*
* @Description:
* Invoke a given raster to scan-convert a given glyph image into a
* target bitmap.
*
* @Input:
* raster ::
* A handle to the raster object.
*
* params ::
* A pointer to an @FT_Raster_Params structure used to
* store the rendering parameters.
*
* @Return:
* Error code. 0~means success.
*
* @Note:
* The exact format of the source image depends on the raster's glyph
* format defined in its @FT_Raster_Funcs structure. It can be an
* @FT_Outline or anything else in order to support a large array of
* glyph formats.
*
* Note also that the render function can fail and return a
* `FT_Err_Unimplemented_Feature' error code if the raster used does
* not support direct composition.
*
* XXX: For now, the standard raster doesn't support direct
* composition but this should change for the final release (see
* the files `demos/src/ftgrays.c' and `demos/src/ftgrays2.c'
* for examples of distinct implementations that support direct
* composition).
*/
typedef int
(*FT_Raster_RenderFunc)( FT_Raster raster,
const FT_Raster_Params* params );
#define FT_Raster_Render_Func FT_Raster_RenderFunc
/**************************************************************************
*
* @Struct:
* FT_Raster_Funcs
*
* @Description:
* A structure used to describe a given raster class to the library.
*
* @Fields:
* glyph_format ::
* The supported glyph format for this raster.
*
* raster_new ::
* The raster constructor.
*
* raster_reset ::
* Used to reset the render pool within the raster.
*
* raster_render ::
* A function to render a glyph into a given bitmap.
*
* raster_done ::
* The raster destructor.
*/
typedef struct FT_Raster_Funcs_
{
FT_Glyph_Format glyph_format;
FT_Raster_NewFunc raster_new;
FT_Raster_ResetFunc raster_reset;
FT_Raster_SetModeFunc raster_set_mode;
FT_Raster_RenderFunc raster_render;
FT_Raster_DoneFunc raster_done;
} FT_Raster_Funcs;
/* */
FT_END_HEADER
#endif /* FTIMAGE_H_ */
/* END */
/* Local Variables: */
/* coding: utf-8 */
/* End: */