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[ft-devel] Possible implementation error: FT_Bitmap_Convert() does not h
[ft-devel] Possible implementation error: FT_Bitmap_Convert() does not handle pixel modes FT_PIXEL_MODE_LCD and FT_PIXEL_MODE_LCD_V
Mon, 5 Jan 2009 10:32:56 +0700
To freetype maintainers,
In developing the test for the freetype function FT_Bitmap_Convert(), we
have encountered the following possible implementation error.
The specification for FT_Bitmap_Convert() stated that:
FT_EXPORT( FT_Error ) FT_Bitmap_Convert(
const FT_Bitmap *source,
FT_Int alignment );
This function converts a bitmap object with depth 1bpp, 2bpp, 4bpp, or 8bpp
to a bitmap object with depth 8bpp., making the number of used bytes per
line (a.k.a. the `pitch') a multiple of `alignment'."
FreeType error code. 0 means success."
Where as part of the source FT_Bitmap*, the different pixel-modes are
defined as follows:
typedef enum FT_Pixel_Mode_
FT_PIXEL_MODE_NONE = 0,
FT_PIXEL_MODE_MAX /* do not remove */
However, when we called this function to convert a bitmap with pixel-mode of
the type FT_PIXEL_MODE_LCD or FT_PIXEL_MODE_LCD_V, the error code 6
(FT_Err_Invalid_Argument) is returned.
There is an inconsistency between the spec and the implementation: It looks
like FT_Bitmap_Convert() does not handle pixel modes FT_PIXEL_MODE_LCD and
We have tested this on 32-bit and 64-bit x86 based test systems running
under the following distros OpenSuSE 11 (32 bit), Ubuntu 8.04 (ia32), RHEL52
x86-64, SLES 10.1 (32bit), Fedora 9 (32bit) with freetype 2.1.10 and
To help demonstrate the alleged-bug, we have included with this email:
a) a c program bitmap_convert.c and
b) a snippet of the free type function FT_Bitmap_Convert() that we
found on the web.
To reproduce use
bitmap_convert FreeMono.ttf M FT_RENDER_MODE_LCD 4
bitmap_convert FreeMono.ttf M FT_RENDER_MODE_LCD_V 4
Where the specified font file (FreeMono.ttf) should be available in the
local directory ./fonts
Thank you very much for your time and please let us know any ruling/finding
that you may have.
Nguyen Trung Chi
NEC Solutions VietNam
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- [ft-devel] Possible implementation error: FT_Bitmap_Convert() does not handle pixel modes FT_PIXEL_MODE_LCD and FT_PIXEL_MODE_LCD_V,
Chi Nguyen <=