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/****************************************************************************
*
* ftcolor.h
*
* FreeType's glyph color management (specification).
*
* Copyright (C) 2018-2020 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 FTCOLOR_H_
#define FTCOLOR_H_
#include <freetype/freetype.h>
#ifdef FREETYPE_H
#error "freetype.h of FreeType 1 has been loaded!"
#error "Please fix the directory search order for header files"
#error "so that freetype.h of FreeType 2 is found first."
#endif
FT_BEGIN_HEADER
/**************************************************************************
*
* @section:
* color_management
*
* @title:
* Glyph Color Management
*
* @abstract:
* Retrieving and manipulating OpenType's 'CPAL' table data.
*
* @description:
* The functions described here allow access and manipulation of color
* palette entries in OpenType's 'CPAL' tables.
*/
/**************************************************************************
*
* @struct:
* FT_Color
*
* @description:
* This structure models a BGRA color value of a 'CPAL' palette entry.
*
* The used color space is sRGB; the colors are not pre-multiplied, and
* alpha values must be explicitly set.
*
* @fields:
* blue ::
* Blue value.
*
* green ::
* Green value.
*
* red ::
* Red value.
*
* alpha ::
* Alpha value, giving the red, green, and blue color's opacity.
*
* @since:
* 2.10
*/
typedef struct FT_Color_
{
FT_Byte blue;
FT_Byte green;
FT_Byte red;
FT_Byte alpha;
} FT_Color;
/**************************************************************************
*
* @enum:
* FT_PALETTE_XXX
*
* @description:
* A list of bit field constants used in the `palette_flags` array of the
* @FT_Palette_Data structure to indicate for which background a palette
* with a given index is usable.
*
* @values:
* FT_PALETTE_FOR_LIGHT_BACKGROUND ::
* The palette is appropriate to use when displaying the font on a
* light background such as white.
*
* FT_PALETTE_FOR_DARK_BACKGROUND ::
* The palette is appropriate to use when displaying the font on a dark
* background such as black.
*
* @since:
* 2.10
*/
#define FT_PALETTE_FOR_LIGHT_BACKGROUND 0x01
#define FT_PALETTE_FOR_DARK_BACKGROUND 0x02
/**************************************************************************
*
* @struct:
* FT_Palette_Data
*
* @description:
* This structure holds the data of the 'CPAL' table.
*
* @fields:
* num_palettes ::
* The number of palettes.
*
* palette_name_ids ::
* An optional read-only array of palette name IDs with `num_palettes`
* elements, corresponding to entries like 'dark' or 'light' in the
* font's 'name' table.
*
* An empty name ID in the 'CPAL' table gets represented as value
* 0xFFFF.
*
* `NULL` if the font's 'CPAL' table doesn't contain appropriate data.
*
* palette_flags ::
* An optional read-only array of palette flags with `num_palettes`
* elements. Possible values are an ORed combination of
* @FT_PALETTE_FOR_LIGHT_BACKGROUND and
* @FT_PALETTE_FOR_DARK_BACKGROUND.
*
* `NULL` if the font's 'CPAL' table doesn't contain appropriate data.
*
* num_palette_entries ::
* The number of entries in a single palette. All palettes have the
* same size.
*
* palette_entry_name_ids ::
* An optional read-only array of palette entry name IDs with
* `num_palette_entries`. In each palette, entries with the same index
* have the same function. For example, index~0 might correspond to
* string 'outline' in the font's 'name' table to indicate that this
* palette entry is used for outlines, index~1 might correspond to
* 'fill' to indicate the filling color palette entry, etc.
*
* An empty entry name ID in the 'CPAL' table gets represented as value
* 0xFFFF.
*
* `NULL` if the font's 'CPAL' table doesn't contain appropriate data.
*
* @note:
* Use function @FT_Get_Sfnt_Name to map name IDs and entry name IDs to
* name strings.
*
* Use function @FT_Palette_Select to get the colors associated with a
* palette entry.
*
* @since:
* 2.10
*/
typedef struct FT_Palette_Data_ {
FT_UShort num_palettes;
const FT_UShort* palette_name_ids;
const FT_UShort* palette_flags;
FT_UShort num_palette_entries;
const FT_UShort* palette_entry_name_ids;
} FT_Palette_Data;
/**************************************************************************
*
* @function:
* FT_Palette_Data_Get
*
* @description:
* Retrieve the face's color palette data.
*
* @input:
* face ::
* The source face handle.
*
* @output:
* apalette ::
* A pointer to an @FT_Palette_Data structure.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* All arrays in the returned @FT_Palette_Data structure are read-only.
*
* This function always returns an error if the config macro
* `TT_CONFIG_OPTION_COLOR_LAYERS` is not defined in `ftoption.h`.
*
* @since:
* 2.10
*/
FT_EXPORT( FT_Error )
FT_Palette_Data_Get( FT_Face face,
FT_Palette_Data *apalette );
/**************************************************************************
*
* @function:
* FT_Palette_Select
*
* @description:
* This function has two purposes.
*
* (1) It activates a palette for rendering color glyphs, and
*
* (2) it retrieves all (unmodified) color entries of this palette. This
* function returns a read-write array, which means that a calling
* application can modify the palette entries on demand.
*
* A corollary of (2) is that calling the function, then modifying some
* values, then calling the function again with the same arguments resets
* all color entries to the original 'CPAL' values; all user modifications
* are lost.
*
* @input:
* face ::
* The source face handle.
*
* palette_index ::
* The palette index.
*
* @output:
* apalette ::
* An array of color entries for a palette with index `palette_index`,
* having `num_palette_entries` elements (as found in the
* `FT_Palette_Data` structure). If `apalette` is set to `NULL`, no
* array gets returned (and no color entries can be modified).
*
* In case the font doesn't support color palettes, `NULL` is returned.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* The array pointed to by `apalette_entries` is owned and managed by
* FreeType.
*
* This function always returns an error if the config macro
* `TT_CONFIG_OPTION_COLOR_LAYERS` is not defined in `ftoption.h`.
*
* @since:
* 2.10
*/
FT_EXPORT( FT_Error )
FT_Palette_Select( FT_Face face,
FT_UShort palette_index,
FT_Color* *apalette );
/**************************************************************************
*
* @function:
* FT_Palette_Set_Foreground_Color
*
* @description:
* 'COLR' uses palette index 0xFFFF to indicate a 'text foreground
* color'. This function sets this value.
*
* @input:
* face ::
* The source face handle.
*
* foreground_color ::
* An `FT_Color` structure to define the text foreground color.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* If this function isn't called, the text foreground color is set to
* white opaque (BGRA value 0xFFFFFFFF) if
* @FT_PALETTE_FOR_DARK_BACKGROUND is present for the current palette,
* and black opaque (BGRA value 0x000000FF) otherwise, including the case
* that no palette types are available in the 'CPAL' table.
*
* This function always returns an error if the config macro
* `TT_CONFIG_OPTION_COLOR_LAYERS` is not defined in `ftoption.h`.
*
* @since:
* 2.10
*/
FT_EXPORT( FT_Error )
FT_Palette_Set_Foreground_Color( FT_Face face,
FT_Color foreground_color );
/* */
FT_END_HEADER
#endif /* FTCOLOR_H_ */
/* END */
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