freetype

Official mirror of https://gitlab.freedesktop.org/freetype/freetype

Werner Lemberg 7227114043 Fix B/W rasterization of subglyphs with different drop-out modes. Normally, the SCANMODE instruction (if present) to set the drop-out mode in a TrueType font is located in the `prep' table only and thus valid for all glyphs. However, there are fonts like `pala.ttf' which additionally contain this instruction in the hinting code of some glyphs (but not all). As a result it can happen that a composite glyph needs multiple drop-out modes for its subglyphs since the rendering state gets reset for each subglyph. FreeType collects the hinted outlines from all subglyphs, then it sends the data to the rasterizer. It also sends the drop-out mode -- after hinting has been applied -- and here is the error: It sends the drop-out mode of the last subglyph only; drop-out modes of all other subglyphs are lost. This patch fixes the problem; it adds a second, alternative mechanism to pass the drop-out mode: For each contour, the rasterizer now checks the first `tags' array element. If bit 2 is set, bits 5-7 contain the contour's drop-out mode, overriding the global drop-out mode. * include/freetype/ftimage.h (FT_CURVE_TAG_HAS_SCANMODE): New macro. * src/truetype/ttgload.c (TT_Hint_Glyph): Store drop-out mode in `tags[0]'. * src/raster/ftraster.c (Flow_Up, Overshoot_Top, Overshoot_Bottom): Use bits 3-5 instead of 0-2. (New_Profile): Set the drop-out mode in the profile's `flags' field. (Decompose_Curve): Check `tags[0]' and set `dropOutControl' if necessary. (Vertical_Sweep_Drop, Horizontal_Sweep_Drop, Horizontal_Gray_Sweep_Drop, Draw_Sweep): Use the profile's drop-out mode.	16 years ago
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freetype	Fix B/W rasterization of subglyphs with different drop-out modes.	16 years ago
ft2build.h	…

Werner Lemberg 7227114043 Fix B/W rasterization of subglyphs with different drop-out modes.

Normally, the SCANMODE instruction (if present) to set the drop-out
mode in a TrueType font is located in the `prep' table only and thus
valid for all glyphs.  However, there are fonts like `pala.ttf'
which additionally contain this instruction in the hinting code of
some glyphs (but not all).  As a result it can happen that a
composite glyph needs multiple drop-out modes for its subglyphs
since the rendering state gets reset for each subglyph.

FreeType collects the hinted outlines from all subglyphs, then it
sends the data to the rasterizer.  It also sends the drop-out mode
-- after hinting has been applied -- and here is the error: It sends
the drop-out mode of the last subglyph only; drop-out modes of all
other subglyphs are lost.

This patch fixes the problem; it adds a second, alternative
mechanism to pass the drop-out mode: For each contour, the
rasterizer now checks the first `tags' array element.  If bit 2 is
set, bits 5-7 contain the contour's drop-out mode, overriding the
global drop-out mode.

* include/freetype/ftimage.h (FT_CURVE_TAG_HAS_SCANMODE): New macro.

* src/truetype/ttgload.c (TT_Hint_Glyph): Store drop-out mode in
`tags[0]'.

* src/raster/ftraster.c (Flow_Up, Overshoot_Top, Overshoot_Bottom):
Use bits 3-5 instead of 0-2.
(New_Profile): Set the drop-out mode in the profile's `flags' field.
(Decompose_Curve): Check `tags[0]' and set `dropOutControl' if
necessary.
(Vertical_Sweep_Drop, Horizontal_Sweep_Drop,
Horizontal_Gray_Sweep_Drop, Draw_Sweep): Use the profile's drop-out
mode.

16 years ago

freetype

Fix B/W rasterization of subglyphs with different drop-out modes.

16 years ago

ft2build.h

…