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kc3-lang/freetype/src/sdf/ftbsdf.c
luz paz
- src/sdf/ftbsdf.c
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/**************************************************************************** * * ftbsdf.c * * Signed Distance Field support for bitmap fonts (body only). * * Copyright (C) 2020-2024 by * David Turner, Robert Wilhelm, and Werner Lemberg. * * Written by Anuj Verma. * * 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. * */ #include <freetype/internal/ftobjs.h> #include <freetype/internal/ftdebug.h> #include <freetype/internal/ftmemory.h> #include <freetype/fttrigon.h> #include "ftsdf.h" #include "ftsdferrs.h" #include "ftsdfcommon.h" /************************************************************************** * * A brief technical overview of how the BSDF rasterizer works * ----------------------------------------------------------- * * [Notes]: * * SDF stands for Signed Distance Field everywhere. * * * BSDF stands for Bitmap to Signed Distance Field rasterizer. * * * This renderer converts rasterized bitmaps to SDF. There is another * renderer called 'sdf', which generates SDF directly from outlines; * see file `ftsdf.c` for more. * * * The idea of generating SDF from bitmaps is taken from two research * papers, where one is dependent on the other: * * - Per-Erik Danielsson: Euclidean Distance Mapping * http://webstaff.itn.liu.se/~stegu/JFA/Danielsson.pdf * * From this paper we use the eight-point sequential Euclidean * distance mapping (8SED). This is the heart of the process used * in this rasterizer. * * - Stefan Gustavson, Robin Strand: Anti-aliased Euclidean distance transform. * http://weber.itn.liu.se/~stegu/aadist/edtaa_preprint.pdf * * The original 8SED algorithm discards the pixels' alpha values, * which can contain information about the actual outline of the * glyph. This paper takes advantage of those alpha values and * approximates outline pretty accurately. * * * This rasterizer also works for monochrome bitmaps. However, the * result is not as accurate since we don't have any way to * approximate outlines from binary bitmaps. * * ======================================================================== * * Generating SDF from bitmap is done in several steps. * * (1) The only information we have is the bitmap itself. It can * be monochrome or anti-aliased. If it is anti-aliased, pixel values * are nothing but coverage values. These coverage values can be used * to extract information about the outline of the image. For * example, if the pixel's alpha value is 0.5, then we can safely * assume that the outline passes through the center of the pixel. * * (2) Find edge pixels in the bitmap (see `bsdf_is_edge` for more). For * all edge pixels we use the Anti-aliased Euclidean distance * transform algorithm and compute approximate edge distances (see * `compute_edge_distance` and/or the second paper for more). * * (3) Now that we have computed approximate distances for edge pixels we * use the 8SED algorithm to basically sweep the entire bitmap and * compute distances for the rest of the pixels. (Since the algorithm * is pretty convoluted it is only explained briefly in a comment to * function `edt8`. To see the actual algorithm refer to the first * paper.) * * (4) Finally, compute the sign for each pixel. This is done in function * `finalize_sdf`. The basic idea is that if a pixel's original * alpha/coverage value is greater than 0.5 then it is 'inside' (and * 'outside' otherwise). * * Pseudo Code: * * ``` * b = source bitmap; * t = target bitmap; * dm = list of distances; // dimension equal to b * * foreach grid_point (x, y) in b: * { * if (is_edge(x, y)): * dm = approximate_edge_distance(b, x, y); * * // do the 8SED on the distances * edt8(dm); * * // determine the signs * determine_signs(dm): * * // copy SDF data to the target bitmap * copy(dm to t); * } * */ /************************************************************************** * * The macro FT_COMPONENT is used in trace mode. It is an implicit * parameter of the FT_TRACE() and FT_ERROR() macros, used to print/log * messages during execution. */ #undef FT_COMPONENT #define FT_COMPONENT bsdf /************************************************************************** * * useful macros * */ #define ONE 65536 /* 1 in 16.16 */ /************************************************************************** * * structs * */ /************************************************************************** * * @Struct: * BSDF_TRaster * * @Description: * This struct is used in place of @FT_Raster and is stored within the * internal FreeType renderer struct. While rasterizing this is passed * to the @FT_Raster_RenderFunc function, which then can be used however * we want. * * @Fields: * memory :: * Used internally to allocate intermediate memory while raterizing. * */ typedef struct BSDF_TRaster_ { FT_Memory memory; } BSDF_TRaster, *BSDF_PRaster; /************************************************************************** * * @Struct: * ED * * @Description: * Euclidean distance. It gets used for Euclidean distance transforms; * it can also be interpreted as an edge distance. * * @Fields: * dist :: * Vector length of the `prox` parameter. Can be squared or absolute * depending on the `USE_SQUARED_DISTANCES` macro defined in file * `ftsdfcommon.h`. * * prox :: * Vector to the nearest edge. Can also be interpreted as shortest * distance of a point. * * alpha :: * Alpha value of the original bitmap from which we generate SDF. * Needed for computing the gradient and determining the proper sign * of a pixel. * */ typedef struct ED_ { FT_16D16 dist; FT_16D16_Vec prox; FT_Byte alpha; } ED; /************************************************************************** * * @Struct: * BSDF_Worker * * @Description: * A convenience struct that is passed to functions while generating * SDF; most of those functions require the same parameters. * * @Fields: * distance_map :: * A one-dimensional array that gets interpreted as two-dimensional * one. It contains the Euclidean distances of all points of the * bitmap. * * width :: * Width of the above `distance_map`. * * rows :: * Number of rows in the above `distance_map`. * * params :: * Internal parameters and properties required by the rasterizer. See * file `ftsdf.h` for more. * */ typedef struct BSDF_Worker_ { ED* distance_map; FT_Int width; FT_Int rows; SDF_Raster_Params params; } BSDF_Worker; /************************************************************************** * * initializer * */ static const ED zero_ed = { 0, { 0, 0 }, 0 }; /************************************************************************** * * rasterizer functions * */ /************************************************************************** * * @Function: * bsdf_is_edge * * @Description: * Check whether a pixel is an edge pixel, i.e., whether it is * surrounded by a completely black pixel (zero alpha), and the current * pixel is not a completely black pixel. * * @Input: * dm :: * Array of distances. The parameter must point to the current * pixel, i.e., the pixel that is to be checked for being an edge. * * x :: * The x position of the current pixel. * * y :: * The y position of the current pixel. * * w :: * Width of the bitmap. * * r :: * Number of rows in the bitmap. * * @Return: * 1~if the current pixel is an edge pixel, 0~otherwise. * */ #ifdef CHECK_NEIGHBOR #undef CHECK_NEIGHBOR #endif #define CHECK_NEIGHBOR( x_offset, y_offset ) \ do \ { \ if ( x + x_offset >= 0 && x + x_offset < w && \ y + y_offset >= 0 && y + y_offset < r ) \ { \ num_neighbors++; \ \ to_check = dm + y_offset * w + x_offset; \ if ( to_check->alpha == 0 ) \ { \ is_edge = 1; \ goto Done; \ } \ } \ } while ( 0 ) static FT_Bool bsdf_is_edge( ED* dm, /* distance map */ FT_Int x, /* x index of point to check */ FT_Int y, /* y index of point to check */ FT_Int w, /* width */ FT_Int r ) /* rows */ { FT_Bool is_edge = 0; ED* to_check = NULL; FT_Int num_neighbors = 0; if ( dm->alpha == 0 ) goto Done; if ( dm->alpha > 0 && dm->alpha < 255 ) { is_edge = 1; goto Done; } /* up */ CHECK_NEIGHBOR( 0, -1 ); /* down */ CHECK_NEIGHBOR( 0, 1 ); /* left */ CHECK_NEIGHBOR( -1, 0 ); /* right */ CHECK_NEIGHBOR( 1, 0 ); /* up left */ CHECK_NEIGHBOR( -1, -1 ); /* up right */ CHECK_NEIGHBOR( 1, -1 ); /* down left */ CHECK_NEIGHBOR( -1, 1 ); /* down right */ CHECK_NEIGHBOR( 1, 1 ); if ( num_neighbors != 8 ) is_edge = 1; Done: return is_edge; } #undef CHECK_NEIGHBOR /************************************************************************** * * @Function: * compute_edge_distance * * @Description: * Approximate the outline and compute the distance from `current` * to the approximated outline. * * @Input: * current :: * Array of Euclidean distances. `current` must point to the position * for which the distance is to be calculated. We treat this array as * a two-dimensional array mapped to a one-dimensional array. * * x :: * The x coordinate of the `current` parameter in the array. * * y :: * The y coordinate of the `current` parameter in the array. * * w :: * The width of the distances array. * * r :: * Number of rows in the distances array. * * @Return: * A vector pointing to the approximate edge distance. * * @Note: * This is a computationally expensive function. Try to reduce the * number of calls to this function. Moreover, this must only be used * for edge pixel positions. * */ static FT_16D16_Vec compute_edge_distance( ED* current, FT_Int x, FT_Int y, FT_Int w, FT_Int r ) { /* * This function, based on the paper presented by Stefan Gustavson and * Robin Strand, gets used to approximate edge distances from * anti-aliased bitmaps. * * The algorithm is as follows. * * (1) In anti-aliased images, the pixel's alpha value is the coverage * of the pixel by the outline. For example, if the alpha value is * 0.5f we can assume that the outline passes through the center of * the pixel. * * (2) For this reason we can use that alpha value to approximate the real * distance of the pixel to edge pretty accurately. A simple * approximation is `(0.5f - alpha)`, assuming that the outline is * parallel to the x or y~axis. However, in this algorithm we use a * different approximation which is quite accurate even for * non-axis-aligned edges. * * (3) The only remaining piece of information that we cannot * approximate directly from the alpha is the direction of the edge. * This is where we use Sobel's operator to compute the gradient of * the pixel. The gradient give us a pretty good approximation of * the edge direction. We use a 3x3 kernel filter to compute the * gradient. * * (4) After the above two steps we have both the direction and the * distance to the edge which is used to generate the Signed * Distance Field. * * References: * * - Anti-Aliased Euclidean Distance Transform: * http://weber.itn.liu.se/~stegu/aadist/edtaa_preprint.pdf * - Sobel Operator: * https://en.wikipedia.org/wiki/Sobel_operator */ FT_16D16_Vec g = { 0, 0 }; FT_16D16 dist, current_alpha; FT_16D16 a1, temp; FT_16D16 gx, gy; FT_16D16 alphas[9]; /* Since our spread cannot be 0, this condition */ /* can never be true. */ if ( x <= 0 || x >= w - 1 || y <= 0 || y >= r - 1 ) return g; /* initialize the alphas */ alphas[0] = 256 * (FT_16D16)current[-w - 1].alpha; alphas[1] = 256 * (FT_16D16)current[-w ].alpha; alphas[2] = 256 * (FT_16D16)current[-w + 1].alpha; alphas[3] = 256 * (FT_16D16)current[ -1].alpha; alphas[4] = 256 * (FT_16D16)current[ 0].alpha; alphas[5] = 256 * (FT_16D16)current[ 1].alpha; alphas[6] = 256 * (FT_16D16)current[ w - 1].alpha; alphas[7] = 256 * (FT_16D16)current[ w ].alpha; alphas[8] = 256 * (FT_16D16)current[ w + 1].alpha; current_alpha = alphas[4]; /* Compute the gradient using the Sobel operator. */ /* In this case we use the following 3x3 filters: */ /* */ /* For x: | -1 0 -1 | */ /* | -root(2) 0 root(2) | */ /* | -1 0 1 | */ /* */ /* For y: | -1 -root(2) -1 | */ /* | 0 0 0 | */ /* | 1 root(2) 1 | */ /* */ /* [Note]: 92681 is root(2) in 16.16 format. */ g.x = -alphas[0] - FT_MulFix( alphas[3], 92681 ) - alphas[6] + alphas[2] + FT_MulFix( alphas[5], 92681 ) + alphas[8]; g.y = -alphas[0] - FT_MulFix( alphas[1], 92681 ) - alphas[2] + alphas[6] + FT_MulFix( alphas[7], 92681 ) + alphas[8]; FT_Vector_NormLen( &g ); /* The gradient gives us the direction of the */ /* edge for the current pixel. Once we have the */ /* approximate direction of the edge, we can */ /* approximate the edge distance much better. */ if ( g.x == 0 || g.y == 0 ) dist = ONE / 2 - alphas[4]; else { gx = g.x; gy = g.y; gx = FT_ABS( gx ); gy = FT_ABS( gy ); if ( gx < gy ) { temp = gx; gx = gy; gy = temp; } a1 = FT_DivFix( gy, gx ) / 2; if ( current_alpha < a1 ) dist = ( gx + gy ) / 2 - square_root( 2 * FT_MulFix( gx, FT_MulFix( gy, current_alpha ) ) ); else if ( current_alpha < ( ONE - a1 ) ) dist = FT_MulFix( ONE / 2 - current_alpha, gx ); else dist = -( gx + gy ) / 2 + square_root( 2 * FT_MulFix( gx, FT_MulFix( gy, ONE - current_alpha ) ) ); } g.x = FT_MulFix( g.x, dist ); g.y = FT_MulFix( g.y, dist ); return g; } /************************************************************************** * * @Function: * bsdf_approximate_edge * * @Description: * Loops over all the pixels and call `compute_edge_distance` only for * edge pixels. This makes the process a lot faster since * `compute_edge_distance` uses functions such as `FT_Vector_NormLen', * which are quite slow. * * @InOut: * worker :: * Contains the distance map as well as all the relevant parameters * required by the function. * * @Return: * FreeType error, 0 means success. * * @Note: * The function directly manipulates `worker->distance_map`. * */ static FT_Error bsdf_approximate_edge( BSDF_Worker* worker ) { FT_Error error = FT_Err_Ok; FT_Int i, j; FT_Int index; ED* ed; if ( !worker || !worker->distance_map ) { error = FT_THROW( Invalid_Argument ); goto Exit; } ed = worker->distance_map; for ( j = 0; j < worker->rows; j++ ) { for ( i = 0; i < worker->width; i++ ) { index = j * worker->width + i; if ( bsdf_is_edge( worker->distance_map + index, i, j, worker->width, worker->rows ) ) { /* approximate the edge distance for edge pixels */ ed[index].prox = compute_edge_distance( ed + index, i, j, worker->width, worker->rows ); ed[index].dist = VECTOR_LENGTH_16D16( ed[index].prox ); } else { /* for non-edge pixels assign far away distances */ ed[index].dist = 400 * ONE; ed[index].prox.x = 200 * ONE; ed[index].prox.y = 200 * ONE; } } } Exit: return error; } /************************************************************************** * * @Function: * bsdf_init_distance_map * * @Description: * Initialize the distance map according to the '8-point sequential * Euclidean distance mapping' (8SED) algorithm. Basically it copies * the `source` bitmap alpha values to the `distance_map->alpha` * parameter of `worker`. * * @Input: * source :: * Source bitmap to copy the data from. * * @Output: * worker :: * Target distance map to copy the data to. * * @Return: * FreeType error, 0 means success. * */ static FT_Error bsdf_init_distance_map( const FT_Bitmap* source, BSDF_Worker* worker ) { FT_Error error = FT_Err_Ok; FT_Int x_diff, y_diff; FT_Int t_i, t_j, s_i, s_j; FT_Byte* s; ED* t; /* again check the parameters (probably unnecessary) */ if ( !source || !worker ) { error = FT_THROW( Invalid_Argument ); goto Exit; } /* Because of the way we convert a bitmap to SDF, */ /* i.e., aligning the source to the center of the */ /* target, the target's width and rows must be */ /* checked before copying. */ if ( worker->width < (FT_Int)source->width || worker->rows < (FT_Int)source->rows ) { error = FT_THROW( Invalid_Argument ); goto Exit; } /* check pixel mode */ if ( source->pixel_mode == FT_PIXEL_MODE_NONE ) { FT_ERROR(( "bsdf_copy_source_to_target:" " Invalid pixel mode of source bitmap" )); error = FT_THROW( Invalid_Argument ); goto Exit; } #ifdef FT_DEBUG_LEVEL_TRACE if ( source->pixel_mode == FT_PIXEL_MODE_MONO ) { FT_TRACE0(( "bsdf_copy_source_to_target:" " The `bsdf' renderer can convert monochrome\n" )); FT_TRACE0(( " " " bitmaps to SDF but the results are not perfect\n" )); FT_TRACE0(( " " " because there is no way to approximate actual\n" )); FT_TRACE0(( " " " outlines from monochrome bitmaps. Consider\n" )); FT_TRACE0(( " " " using an anti-aliased bitmap instead.\n" )); } #endif /* Calculate the width and row differences */ /* between target and source. */ x_diff = worker->width - (int)source->width; y_diff = worker->rows - (int)source->rows; x_diff /= 2; y_diff /= 2; t = (ED*)worker->distance_map; s = source->buffer; /* For now we only support pixel mode `FT_PIXEL_MODE_MONO` */ /* and `FT_PIXEL_MODE_GRAY`. More will be added later. */ /* */ /* [NOTE]: We can also use @FT_Bitmap_Convert to convert */ /* bitmap to 8bpp. To avoid extra allocation and */ /* since the target bitmap can be 16bpp we manually */ /* convert the source bitmap to the desired bpp. */ switch ( source->pixel_mode ) { case FT_PIXEL_MODE_MONO: { FT_Int t_width = worker->width; FT_Int t_rows = worker->rows; FT_Int s_width = (int)source->width; FT_Int s_rows = (int)source->rows; for ( t_j = 0; t_j < t_rows; t_j++ ) { for ( t_i = 0; t_i < t_width; t_i++ ) { FT_Int t_index = t_j * t_width + t_i; FT_Int s_index; FT_Int div, mod; FT_Byte pixel, byte; t[t_index] = zero_ed; s_i = t_i - x_diff; s_j = t_j - y_diff; /* Assign 0 to padding similar to */ /* the source bitmap. */ if ( s_i < 0 || s_i >= s_width || s_j < 0 || s_j >= s_rows ) continue; if ( worker->params.flip_y ) s_index = ( s_rows - s_j - 1 ) * source->pitch; else s_index = s_j * source->pitch; div = s_index + s_i / 8; mod = 7 - s_i % 8; pixel = s[div]; byte = (FT_Byte)( 1 << mod ); t[t_index].alpha = pixel & byte ? 255 : 0; } } } break; case FT_PIXEL_MODE_GRAY: { FT_Int t_width = worker->width; FT_Int t_rows = worker->rows; FT_Int s_width = (int)source->width; FT_Int s_rows = (int)source->rows; /* loop over all pixels and assign pixel values from source */ for ( t_j = 0; t_j < t_rows; t_j++ ) { for ( t_i = 0; t_i < t_width; t_i++ ) { FT_Int t_index = t_j * t_width + t_i; FT_Int s_index; t[t_index] = zero_ed; s_i = t_i - x_diff; s_j = t_j - y_diff; /* Assign 0 to padding similar to */ /* the source bitmap. */ if ( s_i < 0 || s_i >= s_width || s_j < 0 || s_j >= s_rows ) continue; if ( worker->params.flip_y ) s_index = ( s_rows - s_j - 1 ) * s_width + s_i; else s_index = s_j * s_width + s_i; /* simply copy the alpha values */ t[t_index].alpha = s[s_index]; } } } break; default: FT_ERROR(( "bsdf_copy_source_to_target:" " unsopported pixel mode of source bitmap\n" )); error = FT_THROW( Unimplemented_Feature ); break; } Exit: return error; } /************************************************************************** * * @Function: * compare_neighbor * * @Description: * Compare neighbor pixel (which is defined by the offset) and update * `current` distance if the new distance is shorter than the original. * * @Input: * x_offset :: * X offset of the neighbor to be checked. The offset is relative to * the `current`. * * y_offset :: * Y offset of the neighbor to be checked. The offset is relative to * the `current`. * * width :: * Width of the `current` array. * * @InOut: * current :: * Pointer into array of distances. This parameter must point to the * position whose neighbor is to be checked. The array is treated as * a two-dimensional array. * */ static void compare_neighbor( ED* current, FT_Int x_offset, FT_Int y_offset, FT_Int width ) { ED* to_check; FT_16D16 dist; FT_16D16_Vec dist_vec; to_check = current + ( y_offset * width ) + x_offset; /* * While checking for the nearest point we first approximate the * distance of `current` by adding the deviation (which is sqrt(2) at * most). Only if the new value is less than the current value we * calculate the actual distances using `FT_Vector_Length`. This last * step can be omitted by using squared distances. */ /* * Approximate the distance. We subtract 1 to avoid precision errors, * which could happen because the two directions can be opposite. */ dist = to_check->dist - ONE; if ( dist < current->dist ) { dist_vec = to_check->prox; dist_vec.x += x_offset * ONE; dist_vec.y += y_offset * ONE; dist = VECTOR_LENGTH_16D16( dist_vec ); if ( dist < current->dist ) { current->dist = dist; current->prox = dist_vec; } } } /************************************************************************** * * @Function: * first_pass * * @Description: * First pass of the 8SED algorithm. Loop over the bitmap from top to * bottom and scan each row left to right, updating the distances in * `worker->distance_map`. * * @InOut: * worker:: * Contains all the relevant parameters. * */ static void first_pass( BSDF_Worker* worker ) { FT_Int i, j; /* iterators */ FT_Int w, r; /* width, rows */ ED* dm; /* distance map */ dm = worker->distance_map; w = worker->width; r = worker->rows; /* Start scanning from top to bottom and sweep each */ /* row back and forth comparing the distances of the */ /* neighborhood. Leave the first row as it has no top */ /* neighbor; it will be covered in the second scan of */ /* the image (from bottom to top). */ for ( j = 1; j < r; j++ ) { FT_Int index; ED* current; /* Forward pass of rows (left -> right). Leave the first */ /* column, which gets covered in the backward pass. */ for ( i = 1; i < w - 1; i++ ) { index = j * w + i; current = dm + index; /* left-up */ compare_neighbor( current, -1, -1, w ); /* up */ compare_neighbor( current, 0, -1, w ); /* up-right */ compare_neighbor( current, 1, -1, w ); /* left */ compare_neighbor( current, -1, 0, w ); } /* Backward pass of rows (right -> left). Leave the last */ /* column, which was already covered in the forward pass. */ for ( i = w - 2; i >= 0; i-- ) { index = j * w + i; current = dm + index; /* right */ compare_neighbor( current, 1, 0, w ); } } } /************************************************************************** * * @Function: * second_pass * * @Description: * Second pass of the 8SED algorithm. Loop over the bitmap from bottom * to top and scan each row left to right, updating the distances in * `worker->distance_map`. * * @InOut: * worker:: * Contains all the relevant parameters. * */ static void second_pass( BSDF_Worker* worker ) { FT_Int i, j; /* iterators */ FT_Int w, r; /* width, rows */ ED* dm; /* distance map */ dm = worker->distance_map; w = worker->width; r = worker->rows; /* Start scanning from bottom to top and sweep each */ /* row back and forth comparing the distances of the */ /* neighborhood. Leave the last row as it has no down */ /* neighbor; it is already covered in the first scan */ /* of the image (from top to bottom). */ for ( j = r - 2; j >= 0; j-- ) { FT_Int index; ED* current; /* Forward pass of rows (left -> right). Leave the first */ /* column, which gets covered in the backward pass. */ for ( i = 1; i < w - 1; i++ ) { index = j * w + i; current = dm + index; /* left-up */ compare_neighbor( current, -1, 1, w ); /* up */ compare_neighbor( current, 0, 1, w ); /* up-right */ compare_neighbor( current, 1, 1, w ); /* left */ compare_neighbor( current, -1, 0, w ); } /* Backward pass of rows (right -> left). Leave the last */ /* column, which was already covered in the forward pass. */ for ( i = w - 2; i >= 0; i-- ) { index = j * w + i; current = dm + index; /* right */ compare_neighbor( current, 1, 0, w ); } } } /************************************************************************** * * @Function: * edt8 * * @Description: * Compute the distance map of the a bitmap. Execute both first and * second pass of the 8SED algorithm. * * @InOut: * worker:: * Contains all the relevant parameters. * * @Return: * FreeType error, 0 means success. * */ static FT_Error edt8( BSDF_Worker* worker ) { FT_Error error = FT_Err_Ok; if ( !worker || !worker->distance_map ) { error = FT_THROW( Invalid_Argument ); goto Exit; } /* first scan of the image */ first_pass( worker ); /* second scan of the image */ second_pass( worker ); Exit: return error; } /************************************************************************** * * @Function: * finalize_sdf * * @Description: * Copy the SDF data from `worker->distance_map` to the `target` bitmap. * Also transform the data to output format, (which is 6.10 fixed-point * format at the moment). * * @Input: * worker :: * Contains source distance map and other SDF data. * * @Output: * target :: * Target bitmap to which the SDF data is copied to. * * @Return: * FreeType error, 0 means success. * */ static FT_Error finalize_sdf( BSDF_Worker* worker, const FT_Bitmap* target ) { FT_Error error = FT_Err_Ok; FT_Int w, r; FT_Int i, j; FT_SDFFormat* t_buffer; FT_16D16 sp_sq, spread; if ( !worker || !target ) { error = FT_THROW( Invalid_Argument ); goto Exit; } w = (int)target->width; r = (int)target->rows; t_buffer = (FT_SDFFormat*)target->buffer; if ( w != worker->width || r != worker->rows ) { error = FT_THROW( Invalid_Argument ); goto Exit; } spread = (FT_16D16)FT_INT_16D16( worker->params.spread ); #if USE_SQUARED_DISTANCES sp_sq = (FT_16D16)FT_INT_16D16( worker->params.spread * worker->params.spread ); #else sp_sq = (FT_16D16)FT_INT_16D16( worker->params.spread ); #endif for ( j = 0; j < r; j++ ) { for ( i = 0; i < w; i++ ) { FT_Int index; FT_16D16 dist; FT_SDFFormat final_dist; FT_Char sign; index = j * w + i; dist = worker->distance_map[index].dist; if ( dist < 0 || dist > sp_sq ) dist = sp_sq; #if USE_SQUARED_DISTANCES dist = square_root( dist ); #endif /* We assume that if the pixel is inside a contour */ /* its coverage value must be > 127. */ sign = worker->distance_map[index].alpha < 127 ? -1 : 1; /* flip the sign according to the property */ if ( worker->params.flip_sign ) sign = -sign; /* concatenate from 16.16 to appropriate format */ final_dist = map_fixed_to_sdf( dist * sign, spread ); t_buffer[index] = final_dist; } } Exit: return error; } /************************************************************************** * * interface functions * */ /* called when adding a new module through @FT_Add_Module */ static FT_Error bsdf_raster_new( void* memory_, /* FT_Memory */ FT_Raster* araster_ ) /* BSDF_PRaster* */ { FT_Memory memory = (FT_Memory)memory_; BSDF_PRaster* araster = (BSDF_PRaster*)araster_; FT_Error error; BSDF_PRaster raster = NULL; if ( !FT_NEW( raster ) ) raster->memory = memory; *araster = raster; return error; } /* unused */ static void bsdf_raster_reset( FT_Raster raster, unsigned char* pool_base, unsigned long pool_size ) { FT_UNUSED( raster ); FT_UNUSED( pool_base ); FT_UNUSED( pool_size ); } /* unused */ static FT_Error bsdf_raster_set_mode( FT_Raster raster, unsigned long mode, void* args ) { FT_UNUSED( raster ); FT_UNUSED( mode ); FT_UNUSED( args ); return FT_Err_Ok; } /* called while rendering through @FT_Render_Glyph */ static FT_Error bsdf_raster_render( FT_Raster raster, const FT_Raster_Params* params ) { FT_Error error = FT_Err_Ok; FT_Memory memory = NULL; const FT_Bitmap* source = NULL; const FT_Bitmap* target = NULL; BSDF_TRaster* bsdf_raster = (BSDF_TRaster*)raster; BSDF_Worker worker; const SDF_Raster_Params* sdf_params = (const SDF_Raster_Params*)params; worker.distance_map = NULL; /* check for valid parameters */ if ( !raster || !params ) { error = FT_THROW( Invalid_Argument ); goto Exit; } /* check whether the flag is set */ if ( sdf_params->root.flags != FT_RASTER_FLAG_SDF ) { error = FT_THROW( Raster_Corrupted ); goto Exit; } source = (const FT_Bitmap*)sdf_params->root.source; target = (const FT_Bitmap*)sdf_params->root.target; /* check source and target bitmap */ if ( !source || !target ) { error = FT_THROW( Invalid_Argument ); goto Exit; } memory = bsdf_raster->memory; if ( !memory ) { FT_TRACE0(( "bsdf_raster_render: Raster not set up properly,\n" )); FT_TRACE0(( " unable to find memory handle.\n" )); error = FT_THROW( Invalid_Handle ); goto Exit; } /* check whether spread is set properly */ if ( sdf_params->spread > MAX_SPREAD || sdf_params->spread < MIN_SPREAD ) { FT_TRACE0(( "bsdf_raster_render:" " The `spread' field of `SDF_Raster_Params'\n" )); FT_TRACE0(( " " " is invalid; the value of this field must be\n" )); FT_TRACE0(( " " " within [%d, %d].\n", MIN_SPREAD, MAX_SPREAD )); FT_TRACE0(( " " " Also, you must pass `SDF_Raster_Params'\n" )); FT_TRACE0(( " " " instead of the default `FT_Raster_Params'\n" )); FT_TRACE0(( " " " while calling this function and set the fields\n" )); FT_TRACE0(( " " " accordingly.\n" )); error = FT_THROW( Invalid_Argument ); goto Exit; } /* set up the worker */ /* allocate the distance map */ if ( FT_QALLOC_MULT( worker.distance_map, target->rows, target->width * sizeof ( *worker.distance_map ) ) ) goto Exit; worker.width = (int)target->width; worker.rows = (int)target->rows; worker.params = *sdf_params; FT_CALL( bsdf_init_distance_map( source, &worker ) ); FT_CALL( bsdf_approximate_edge( &worker ) ); FT_CALL( edt8( &worker ) ); FT_CALL( finalize_sdf( &worker, target ) ); FT_TRACE0(( "bsdf_raster_render: Total memory used = %ld\n", worker.width * worker.rows * (long)sizeof ( *worker.distance_map ) )); Exit: if ( worker.distance_map ) FT_FREE( worker.distance_map ); return error; } /* called while deleting `FT_Library` only if the module is added */ static void bsdf_raster_done( FT_Raster raster ) { FT_Memory memory = (FT_Memory)((BSDF_TRaster*)raster)->memory; FT_FREE( raster ); } FT_DEFINE_RASTER_FUNCS( ft_bitmap_sdf_raster, FT_GLYPH_FORMAT_BITMAP, (FT_Raster_New_Func) bsdf_raster_new, /* raster_new */ (FT_Raster_Reset_Func) bsdf_raster_reset, /* raster_reset */ (FT_Raster_Set_Mode_Func)bsdf_raster_set_mode, /* raster_set_mode */ (FT_Raster_Render_Func) bsdf_raster_render, /* raster_render */ (FT_Raster_Done_Func) bsdf_raster_done /* raster_done */ ) /* END */