ref: c91dfa39e8863318f092b4d38b31e7dca32d5b40
parent: 5b631d894c68dc07208cf9cd0817a4584741b8d3
author: Werner Lemberg <[email protected]>
date: Sat Jun 21 02:27:53 EDT 2008
Improve documentation of gray-level rastering and what to do if you need less than 256 gray levels.
--- a/include/freetype/freetype.h
+++ b/include/freetype/freetype.h
@@ -2564,10 +2564,12 @@
/* @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_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 */
--- a/include/freetype/ftimage.h
+++ b/include/freetype/ftimage.h
@@ -129,7 +129,7 @@
/* 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_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_
{--- a/include/freetype/ftoutln.h
+++ b/include/freetype/ftoutln.h
@@ -391,10 +391,15 @@
/* */
/* <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,
@@ -431,6 +436,11 @@
/* The field `params.source' will be set to `outline' before the scan */
/* 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,
--- a/src/smooth/ftgrays.c
+++ b/src/smooth/ftgrays.c
@@ -1616,6 +1616,7 @@
volatile int error = 0;
+
if ( ft_setjmp( ras.jump_buffer ) == 0 )
{error = FT_Outline_Decompose( &ras.outline, &func_interface, &ras );
@@ -1622,9 +1623,7 @@
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;