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Diffstat (limited to 'modules/freetype2/include/freetype/ftimage.h')
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diff --git a/modules/freetype2/include/freetype/ftimage.h b/modules/freetype2/include/freetype/ftimage.h new file mode 100644 index 0000000000..2e8e6734cc --- /dev/null +++ b/modules/freetype2/include/freetype/ftimage.h @@ -0,0 +1,1278 @@ +/**************************************************************************** + * + * ftimage.h + * + * FreeType glyph image formats and default raster interface + * (specification). + * + * Copyright (C) 1996-2023 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_ + + +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 + + /* */ + + /* For debugging, the @FT_Pixel_Mode enumeration must stay in sync */ + /* with the `pixel_modes` array in file `ftobjs.c`. */ + + + /************************************************************************** + * + * @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 used 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_OVERLAP :: + * [Since 2.10.3] This flag indicates that this outline contains + * overlapping contours and the anti-aliased renderer should perform + * oversampling to mitigate possible artifacts. This flag should _not_ + * be set for well designed glyphs without overlaps because it quadruples + * the rendering time. + * + * 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_OVERLAP 0x40 + +#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 & 0x03 ) + + /* see the `tags` field in `FT_Outline` for a description of the values */ +#define FT_CURVE_TAG_ON 0x01 +#define FT_CURVE_TAG_CONIC 0x00 +#define FT_CURVE_TAG_CUBIC 0x02 + +#define FT_CURVE_TAG_HAS_SCANMODE 0x04 + +#define FT_CURVE_TAG_TOUCH_X 0x08 /* reserved for TrueType hinter */ +#define FT_CURVE_TAG_TOUCH_Y 0x10 /* reserved for TrueType hinter */ + +#define FT_CURVE_TAG_TOUCH_BOTH ( FT_CURVE_TAG_TOUCH_X | \ + FT_CURVE_TAG_TOUCH_Y ) + /* values 0x20, 0x40, and 0x80 are reserved */ + + + /* these constants are deprecated; use the corresponding */ + /* `FT_CURVE_TAG_XXX` values instead */ +#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 = ( ( FT_STATIC_BYTE_CAST( unsigned long, _x1 ) << 24 ) | \ + ( FT_STATIC_BYTE_CAST( unsigned long, _x2 ) << 16 ) | \ + ( FT_STATIC_BYTE_CAST( unsigned long, _x3 ) << 8 ) | \ + FT_STATIC_BYTE_CAST( 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. + * + * FT_GLYPH_FORMAT_SVG :: + * [Since 2.12] The glyph is represented by an SVG document in the + * 'SVG~' table. + */ + 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_IMAGE_TAG( FT_GLYPH_FORMAT_SVG, 'S', 'V', 'G', ' ' ) + + } 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 *****/ + /***** *****/ + /*************************************************************************/ + /*************************************************************************/ + /*************************************************************************/ + + + + /************************************************************************** + * + * @section: + * raster + * + * @title: + * Scanline Converter + * + * @abstract: + * How vectorial outlines are converted into bitmaps and pixmaps. + * + * @description: + * A raster or a rasterizer is a scan converter in charge of producing a + * pixel coverage bitmap that can be used as an alpha channel when + * compositing a glyph with a background. FreeType comes with two + * rasterizers: bilevel `raster1` and anti-aliased `smooth` are two + * separate modules. They are usually called from the high-level + * @FT_Load_Glyph or @FT_Render_Glyph functions and produce the entire + * coverage bitmap at once, while staying largely invisible to users. + * + * Instead of working with complete coverage bitmaps, it is also possible + * to intercept consecutive pixel runs on the same scanline with the same + * coverage, called _spans_, and process them individually. Only the + * `smooth` rasterizer permits this when calling @FT_Outline_Render with + * @FT_Raster_Params as described below. + * + * Working with either complete bitmaps or spans it is important to think + * of them as colorless coverage objects suitable as alpha channels to + * blend arbitrary colors with a background. For best results, it is + * recommended to use gamma correction, too. + * + * This section also describes the public API needed to set up alternative + * @FT_Renderer modules. + * + * @order: + * FT_Span + * FT_SpanFunc + * FT_Raster_Params + * FT_RASTER_FLAG_XXX + * + * FT_Raster + * FT_Raster_NewFunc + * FT_Raster_DoneFunc + * FT_Raster_ResetFunc + * FT_Raster_SetModeFunc + * FT_Raster_RenderFunc + * FT_Raster_Funcs + * + */ + + + /************************************************************************** + * + * @struct: + * FT_Span + * + * @description: + * A structure to model a single span of consecutive 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 anti-aliased rasterizer produces coverage values from 0 to 255, + * this is, from completely transparent to completely opaque. + */ + 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 pixel spans on each + * scan line. + * + * @input: + * y :: + * The scanline's upward 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 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 using alpha compositing. It can also be used for + * oversampling and averaging. + */ + 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 and the output will be clipped to its size. + * + * 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. Otherwise, the `clip_box` is + * effectively set to the bounding box and all spans are generated. + * + * FT_RASTER_FLAG_SDF :: + * This flag is set to indicate that a signed distance field glyph + * image should be generated. This is only used while rendering with + * the @FT_RENDER_MODE_SDF render mode. + */ +#define FT_RASTER_FLAG_DEFAULT 0x0 +#define FT_RASTER_FLAG_AA 0x1 +#define FT_RASTER_FLAG_DIRECT 0x2 +#define FT_RASTER_FLAG_CLIP 0x4 +#define FT_RASTER_FLAG_SDF 0x8 + + /* 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 parameters used by a raster's render function, + * passed as an argument to @FT_Outline_Render. + * + * @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 span clipping box expressed in _integer_ pixels + * (not in 26.6 fixed-point units). + * + * @note: + * The @FT_RASTER_FLAG_AA bit flag must be set in the `flags` to + * generate an anti-aliased glyph bitmap, otherwise a monochrome bitmap + * is generated. The `target` should have appropriate pixel mode and its + * dimensions define the clipping region. + * + * If both @FT_RASTER_FLAG_AA and @FT_RASTER_FLAG_DIRECT bit flags + * are set in `flags`, the raster calls an @FT_SpanFunc callback + * `gray_spans` with `user` data as an argument ignoring `target`. This + * allows direct composition over a pre-existing user surface to perform + * the span drawing and composition. To optionally clip the spans, set + * the @FT_RASTER_FLAG_CLIP flag and `clip_box`. The monochrome raster + * does not support the direct mode. + * + * The gray-level rasterizer always uses 256 gray levels. If you want + * fewer gray levels, you have to use @FT_RASTER_FLAG_DIRECT and reduce + * the levels in the callback function. + */ + 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; + + + /************************************************************************** + * + * @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. + * + * @note: + * In FreeType 2, all rasters are now encapsulated within specific + * @FT_Renderer modules and only used in their context. + * + */ + typedef struct FT_RasterRec_* FT_Raster; + + + /************************************************************************** + * + * @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. + */ + 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: */ |