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Code Issues 4 Releases Wiki Activity

Improve documentation of gray-level rastering and what to do if you need 

less than 256 gray levels.
This commit is contained in:
Werner Lemberg 2008-06-21 06:27:53 +00:00
parent 5b631d894c
commit c91dfa39e8
4 changed files with 25 additions and 10 deletions
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7
include/freetype/freetype.h
View File

@ -2564,10 +2564,12 @@ FT_BEGIN_HEADER
/* @FT_GlyphSlotRec structure gives the format of the returned */
/* bitmap. */
/* */
/* All modes except @FT_RENDER_MODE_MONO use 256 levels of opacity. */
/* */
/* <Values> */
/* FT_RENDER_MODE_NORMAL :: */
/* This is the default render mode; it corresponds to 8-bit */
/* anti-aliased bitmaps, using 256 levels of opacity. */
/* anti-aliased bitmaps. */
/* */
/* FT_RENDER_MODE_LIGHT :: */
/* This is equivalent to @FT_RENDER_MODE_NORMAL. It is only */
@ -2576,7 +2578,8 @@ FT_BEGIN_HEADER
/* @FT_LOAD_TARGET_XXX for details. */
/* */
/* FT_RENDER_MODE_MONO :: */
/* This mode corresponds to 1-bit bitmaps. */
/* This mode corresponds to 1-bit bitmaps (with 2 levels of */
/* opacity). */
/* */
/* FT_RENDER_MODE_LCD :: */
/* This mode corresponds to horizontal RGB and BGR sub-pixel */

5
include/freetype/ftimage.h
View File

@ -129,7 +129,7 @@ FT_BEGIN_HEADER
/* 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 value `gray' levels is stored in the `num_bytes' field of */
/* of value `gray' levels is stored in the `num_grays' field of */
/* the @FT_Bitmap structure (it generally is 256). */
/* */
/* FT_PIXEL_MODE_GRAY2 :: */
@ -819,7 +819,8 @@ FT_BEGIN_HEADER
/* @FT_SpanFunc which takes the y-coordinate of the span as a */
/* a parameter. */
/* */
/* The coverage value is always between 0 and 255. */
/* 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_
{

12
include/freetype/ftoutln.h
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@ -391,10 +391,15 @@ FT_BEGIN_HEADER
/* */
/* <Note> */
/* This function does NOT CREATE the bitmap, it only renders an */
/* outline image within the one you pass to it! */
/* outline image within the one you pass to it! Consequently, the */
/* various fields in `abitmap' should be set accordingly. */
/* */
/* It will use the raster corresponding to the default glyph format. */
/* */
/* The value of the `num_grays' field in `abitmap' is ignored. If */
/* you select the gray-level rasterizer, and you want less than 256 */
/* gray levels, you have to use @FT_Outline_Render directly. */
/* */
FT_EXPORT( FT_Error )
FT_Outline_Get_Bitmap( FT_Library library,
FT_Outline* outline,
@ -432,6 +437,11 @@ FT_BEGIN_HEADER
/* converter is called, which means that the value you give to it is */
/* actually ignored. */
/* */
/* The gray-level rasterizer always uses 256 gray levels. If you */
/* want less gray levels, you have to provide your own span callback. */
/* See the @FT_RASTER_FLAG_DIRECT value of the `flags' field in the */
/* @FT_Raster_Params structure for more details. */
/* */
FT_EXPORT( FT_Error )
FT_Outline_Render( FT_Library library,
FT_Outline* outline,

11
src/smooth/ftgrays.c
View File

@ -1616,15 +1616,14 @@
volatile int error = 0;
if ( ft_setjmp( ras.jump_buffer ) == 0 )
{
error = FT_Outline_Decompose( &ras.outline, &func_interface, &ras );
gray_record_cell( RAS_VAR );
}
else
{
error = ErrRaster_Memory_Overflow;
}
return error;
}
@ -1678,10 +1677,12 @@
ras.cubic_level <<= level;
}
/* setup vertical bands */
/* set up vertical bands */
num_bands = (int)( ( ras.max_ey - ras.min_ey ) / ras.band_size );
if ( num_bands == 0 ) num_bands = 1;
if ( num_bands >= 39 ) num_bands = 39;
if ( num_bands == 0 )
num_bands = 1;
if ( num_bands >= 39 )
num_bands = 39;
ras.band_shoot = 0;