[sdf] Add function to copy source bitmap to distance map.
* src/sdf/ftbsdf.c (bsdf_init_distance_map): New function.
This commit is contained in:
Anuj Verma
Werner Lemberg
parent
0f644f38e9
commit
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@ -1,3 +1,9 @@
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2020-08-20 Anuj Verma <anujv@iitbhilai.ac.in>
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[sdf] Add function to copy source bitmap to distance map.
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* src/sdf/ftbsdf.c (bsdf_init_distance_map): New function.
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2020-08-20 Anuj Verma <anujv@iitbhilai.ac.in>
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[sdf] Add functions to compute pixel edge distances.
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201
src/sdf/ftbsdf.c
201
src/sdf/ftbsdf.c
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@ -494,4 +494,205 @@
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return error;
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}
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/**************************************************************************
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*
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* @Function:
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* bsdf_init_distance_map
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*
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* @Description:
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* Initialize the distance map according to the '8-point sequential
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* Euclidean distance mapping' (8SED) algorithm. Basically it copies
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* the `source` bitmap alpha values to the `distance_map->alpha`
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* parameter of `worker`.
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*
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* @Input:
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* source ::
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* Source bitmap to copy the data from.
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*
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* @Output:
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* worker ::
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* Target distance map to copy the data to.
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*
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* @Return:
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* FreeType error, 0 means success.
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*
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*/
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static FT_Error
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bsdf_init_distance_map( const FT_Bitmap* source,
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BSDF_Worker* worker )
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{
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FT_Error error = FT_Err_Ok;
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FT_Int x_diff, y_diff;
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FT_Int t_i, t_j, s_i, s_j;
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FT_Byte* s;
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ED* t;
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/* again check the parameters (probably unnecessary) */
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if ( !source || !worker )
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{
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error = FT_THROW( Invalid_Argument );
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goto Exit;
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}
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/* Because of the way we convert a bitmap to SDF, */
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/* i.e., aligning the source to the center of the */
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/* target, the target's width and rows must be */
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/* checked before copying. */
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if ( worker->width < (FT_Int)source->width ||
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worker->rows < (FT_Int)source->rows )
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{
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error = FT_THROW( Invalid_Argument );
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goto Exit;
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}
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/* check pixel mode */
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if ( source->pixel_mode == FT_PIXEL_MODE_NONE )
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{
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FT_ERROR(( "bsdf_copy_source_to_target:"
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" Invalid pixel mode of source bitmap" ));
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error = FT_THROW( Invalid_Argument );
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goto Exit;
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}
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#ifdef FT_DEBUG_LEVEL_TRACE
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if ( source->pixel_mode == FT_PIXEL_MODE_MONO )
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{
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FT_TRACE0(( "bsdf_copy_source_to_target:"
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" The `bsdf' renderer can convert monochrome\n" ));
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FT_TRACE0(( " "
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" bitmaps to SDF but the results are not perfect\n" ));
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FT_TRACE0(( " "
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" because there is no way to approximate actual\n" ));
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FT_TRACE0(( " "
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" outlines from monochrome bitmaps. Consider\n" ));
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FT_TRACE0(( " "
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" using an anti-aliased bitmap instead.\n" ));
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}
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#endif
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/* Calculate the width and row differences */
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/* between target and source. */
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x_diff = worker->width - source->width;
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y_diff = worker->rows - source->rows;
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x_diff /= 2;
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y_diff /= 2;
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t = (ED*)worker->distance_map;
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s = source->buffer;
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/* For now we only support pixel mode `FT_PIXEL_MODE_MONO` */
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/* and `FT_PIXEL_MODE_GRAY`. More will be added later. */
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/* */
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/* [NOTE]: We can also use @FT_Bitmap_Convert to convert */
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/* bitmap to 8bpp. To avoid extra allocation and */
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/* since the target bitmap can be 16bpp we manually */
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/* convert the source bitmap to the desired bpp. */
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switch ( source->pixel_mode )
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{
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case FT_PIXEL_MODE_MONO:
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{
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FT_Int t_width = worker->width;
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FT_Int t_rows = worker->rows;
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FT_Int s_width = source->width;
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FT_Int s_rows = source->rows;
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for ( t_j = 0; t_j < t_rows; t_j++ )
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{
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for ( t_i = 0; t_i < t_width; t_i++ )
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{
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FT_Int t_index = t_j * t_width + t_i;
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FT_Int s_index;
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FT_Int div, mod;
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FT_Byte pixel, byte;
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t[t_index] = zero_ed;
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s_i = t_i - x_diff;
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s_j = t_j - y_diff;
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/* Assign 0 to padding similar to */
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/* the source bitmap. */
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if ( s_i < 0 || s_i >= s_width ||
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s_j < 0 || s_j >= s_rows )
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continue;
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if ( worker->params.flip_y )
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s_index = ( s_rows - s_j - 1 ) * source->pitch;
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else
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s_index = s_j * source->pitch;
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div = s_index + s_i / 8;
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mod = 7 - s_i % 8;
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pixel = s[div];
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byte = 1 << mod;
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t[t_index].alpha = pixel & byte ? 255 : 0;
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pixel = 0;
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}
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}
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}
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break;
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case FT_PIXEL_MODE_GRAY:
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{
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FT_Int t_width = worker->width;
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FT_Int t_rows = worker->rows;
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FT_Int s_width = source->width;
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FT_Int s_rows = source->rows;
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/* loop over all pixels and assign pixel values from source */
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for ( t_j = 0; t_j < t_rows; t_j++ )
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{
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for ( t_i = 0; t_i < t_width; t_i++ )
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{
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FT_Int t_index = t_j * t_width + t_i;
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FT_Int s_index;
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t[t_index] = zero_ed;
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s_i = t_i - x_diff;
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s_j = t_j - y_diff;
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/* Assign 0 to padding similar to */
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/* the source bitmap. */
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if ( s_i < 0 || s_i >= s_width ||
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s_j < 0 || s_j >= s_rows )
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continue;
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if ( worker->params.flip_y )
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s_index = ( s_rows - s_j - 1 ) * s_width + s_i;
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else
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s_index = s_j * s_width + s_i;
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/* simply copy the alpha values */
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t[t_index].alpha = s[s_index];
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}
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}
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}
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break;
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default:
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FT_ERROR(( "bsdf_copy_source_to_target:"
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" unsopported pixel mode of source bitmap\n" ));
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error = FT_THROW( Unimplemented_Feature );
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break;
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}
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Exit:
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return error;
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}
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/* END */
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