Source code
Revision control
Copy as Markdown
Other Tools
/****************************************************************************
*
* pngshim.c
*
* PNG Bitmap glyph support.
*
* Copyright (C) 2013-2024 by
* Google, Inc.
* Written by Stuart Gill and Behdad Esfahbod.
*
* This file is part of the FreeType project, and may only be used,
* modified, and distributed under the terms of the FreeType project
* license, LICENSE.TXT. By continuing to use, modify, or distribute
* this file you indicate that you have read the license and
* understand and accept it fully.
*
*/
#include <freetype/internal/ftdebug.h>
#include <freetype/internal/ftstream.h>
#include <freetype/tttags.h>
#include FT_CONFIG_STANDARD_LIBRARY_H
#if defined( TT_CONFIG_OPTION_EMBEDDED_BITMAPS ) && \
defined( FT_CONFIG_OPTION_USE_PNG )
/* We always include <setjmp.h>, so make libpng shut up! */
#define PNG_SKIP_SETJMP_CHECK 1
#include <png.h>
#include "pngshim.h"
#include "sferrors.h"
/* This code is freely based on cairo-png.c. There's so many ways */
/* to call libpng, and the way cairo does it is defacto standard. */
static unsigned int
multiply_alpha( unsigned int alpha,
unsigned int color )
{
unsigned int temp = alpha * color + 0x80;
return ( temp + ( temp >> 8 ) ) >> 8;
}
/* Premultiplies data and converts RGBA bytes => BGRA. */
static void
premultiply_data( png_structp png,
png_row_infop row_info,
png_bytep data )
{
unsigned int i = 0, limit;
/* The `vector_size' attribute was introduced in gcc 3.1, which */
/* predates clang; the `__BYTE_ORDER__' preprocessor symbol was */
/* introduced in gcc 4.6 and clang 3.2, respectively. */
/* `__builtin_shuffle' for gcc was introduced in gcc 4.7.0. */
/* */
/* Intel compilers do not currently support __builtin_shuffle; */
/* The Intel check must be first. */
#if !defined( __INTEL_COMPILER ) && \
( ( defined( __GNUC__ ) && \
( ( __GNUC__ >= 5 ) || \
( ( __GNUC__ == 4 ) && ( __GNUC_MINOR__ >= 7 ) ) ) ) || \
( defined( __clang__ ) && \
( ( __clang_major__ >= 4 ) || \
( ( __clang_major__ == 3 ) && ( __clang_minor__ >= 2 ) ) ) ) ) && \
defined( __OPTIMIZE__ ) && \
defined( __SSE__ ) && \
__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
#ifdef __clang__
/* the clang documentation doesn't cover the two-argument case of */
/* `__builtin_shufflevector'; however, it is is implemented since */
/* version 2.8 */
#define vector_shuffle __builtin_shufflevector
#else
#define vector_shuffle __builtin_shuffle
#endif
typedef unsigned short v82 __attribute__(( vector_size( 16 ) ));
if ( row_info->rowbytes > 15 )
{
/* process blocks of 16 bytes in one rush, which gives a nice speed-up */
limit = row_info->rowbytes - 16 + 1;
for ( ; i < limit; i += 16 )
{
unsigned char* base = &data[i];
v82 s, s0, s1, a;
/* clang <= 3.9 can't apply scalar values to vectors */
/* (or rather, it needs a different syntax) */
v82 n0x80 = { 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80 };
v82 n0xFF = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
v82 n8 = { 8, 8, 8, 8, 8, 8, 8, 8 };
v82 ma = { 1, 1, 3, 3, 5, 5, 7, 7 };
v82 o1 = { 0, 0xFF, 0, 0xFF, 0, 0xFF, 0, 0xFF };
v82 m0 = { 1, 0, 3, 2, 5, 4, 7, 6 };
ft_memcpy( &s, base, 16 ); /* RGBA RGBA RGBA RGBA */
s0 = s & n0xFF; /* R B R B R B R B */
s1 = s >> n8; /* G A G A G A G A */
a = vector_shuffle( s1, ma ); /* A A A A A A A A */
s1 |= o1; /* G 1 G 1 G 1 G 1 */
s0 = vector_shuffle( s0, m0 ); /* B R B R B R B R */
s0 *= a;
s1 *= a;
s0 += n0x80;
s1 += n0x80;
s0 = ( s0 + ( s0 >> n8 ) ) >> n8;
s1 = ( s1 + ( s1 >> n8 ) ) >> n8;
s = s0 | ( s1 << n8 );
ft_memcpy( base, &s, 16 );
}
}
#endif /* use `vector_size' */
FT_UNUSED( png );
limit = row_info->rowbytes;
for ( ; i < limit; i += 4 )
{
unsigned char* base = &data[i];
unsigned int alpha = base[3];
if ( alpha == 0 )
base[0] = base[1] = base[2] = base[3] = 0;
else
{
unsigned int red = base[0];
unsigned int green = base[1];
unsigned int blue = base[2];
if ( alpha != 0xFF )
{
red = multiply_alpha( alpha, red );
green = multiply_alpha( alpha, green );
blue = multiply_alpha( alpha, blue );
}
base[0] = (unsigned char)blue;
base[1] = (unsigned char)green;
base[2] = (unsigned char)red;
base[3] = (unsigned char)alpha;
}
}
}
/* Converts RGBx bytes to BGRA. */
static void
convert_bytes_to_data( png_structp png,
png_row_infop row_info,
png_bytep data )
{
unsigned int i;
FT_UNUSED( png );
for ( i = 0; i < row_info->rowbytes; i += 4 )
{
unsigned char* base = &data[i];
unsigned int red = base[0];
unsigned int green = base[1];
unsigned int blue = base[2];
base[0] = (unsigned char)blue;
base[1] = (unsigned char)green;
base[2] = (unsigned char)red;
base[3] = 0xFF;
}
}
/* Use error callback to avoid png writing to stderr. */
static void
error_callback( png_structp png,
png_const_charp error_msg )
{
FT_Error* error = (FT_Error*)png_get_error_ptr( png );
FT_UNUSED( error_msg );
*error = FT_THROW( Out_Of_Memory );
#ifdef PNG_SETJMP_SUPPORTED
ft_longjmp( png_jmpbuf( png ), 1 );
#endif
/* if we get here, then we have no choice but to abort ... */
}
/* Use warning callback to avoid png writing to stderr. */
static void
warning_callback( png_structp png,
png_const_charp error_msg )
{
FT_UNUSED( png );
FT_UNUSED( error_msg );
/* Just ignore warnings. */
}
static void
read_data_from_FT_Stream( png_structp png,
png_bytep data,
png_size_t length )
{
FT_Error error;
png_voidp p = png_get_io_ptr( png );
FT_Stream stream = (FT_Stream)p;
if ( FT_FRAME_ENTER( length ) )
{
FT_Error* e = (FT_Error*)png_get_error_ptr( png );
*e = FT_THROW( Invalid_Stream_Read );
png_error( png, NULL );
/* return; (never reached) */
}
ft_memcpy( data, stream->cursor, length );
FT_FRAME_EXIT();
}
FT_LOCAL_DEF( FT_Error )
Load_SBit_Png( FT_GlyphSlot slot,
FT_Int x_offset,
FT_Int y_offset,
FT_Int pix_bits,
TT_SBit_Metrics metrics,
FT_Memory memory,
FT_Byte* data,
FT_UInt png_len,
FT_Bool populate_map_and_metrics,
FT_Bool metrics_only )
{
FT_Bitmap *map = &slot->bitmap;
FT_Error error = FT_Err_Ok;
FT_StreamRec stream;
png_structp png;
png_infop info;
png_uint_32 imgWidth, imgHeight;
int bitdepth, color_type, interlace;
FT_Int i;
/* `rows` gets modified within a 'setjmp' scope; */
/* we thus need the `volatile` keyword. */
png_byte* *volatile rows = NULL;
if ( x_offset < 0 ||
y_offset < 0 )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
if ( !populate_map_and_metrics &&
( (FT_UInt)x_offset + metrics->width > map->width ||
(FT_UInt)y_offset + metrics->height > map->rows ||
pix_bits != 32 ||
map->pixel_mode != FT_PIXEL_MODE_BGRA ) )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
FT_Stream_OpenMemory( &stream, data, png_len );
png = png_create_read_struct( PNG_LIBPNG_VER_STRING,
&error,
error_callback,
warning_callback );
if ( !png )
{
error = FT_THROW( Out_Of_Memory );
goto Exit;
}
info = png_create_info_struct( png );
if ( !info )
{
error = FT_THROW( Out_Of_Memory );
png_destroy_read_struct( &png, NULL, NULL );
goto Exit;
}
if ( ft_setjmp( png_jmpbuf( png ) ) )
{
error = FT_THROW( Invalid_File_Format );
goto DestroyExit;
}
png_set_read_fn( png, &stream, read_data_from_FT_Stream );
png_read_info( png, info );
png_get_IHDR( png, info,
&imgWidth, &imgHeight,
&bitdepth, &color_type, &interlace,
NULL, NULL );
if ( error ||
( !populate_map_and_metrics &&
( (FT_Int)imgWidth != metrics->width ||
(FT_Int)imgHeight != metrics->height ) ) )
goto DestroyExit;
if ( populate_map_and_metrics )
{
/* reject too large bitmaps similarly to the rasterizer */
if ( imgHeight > 0x7FFF || imgWidth > 0x7FFF )
{
error = FT_THROW( Array_Too_Large );
goto DestroyExit;
}
metrics->width = (FT_UShort)imgWidth;
metrics->height = (FT_UShort)imgHeight;
map->width = metrics->width;
map->rows = metrics->height;
map->pixel_mode = FT_PIXEL_MODE_BGRA;
map->pitch = (int)( map->width * 4 );
map->num_grays = 256;
}
/* convert palette/gray image to rgb */
if ( color_type == PNG_COLOR_TYPE_PALETTE )
png_set_palette_to_rgb( png );
/* expand gray bit depth if needed */
if ( color_type == PNG_COLOR_TYPE_GRAY )
{
#if PNG_LIBPNG_VER >= 10209
png_set_expand_gray_1_2_4_to_8( png );
#else
png_set_gray_1_2_4_to_8( png );
#endif
}
/* transform transparency to alpha */
if ( png_get_valid( png, info, PNG_INFO_tRNS ) )
png_set_tRNS_to_alpha( png );
if ( bitdepth == 16 )
png_set_strip_16( png );
if ( bitdepth < 8 )
png_set_packing( png );
/* convert grayscale to RGB */
if ( color_type == PNG_COLOR_TYPE_GRAY ||
color_type == PNG_COLOR_TYPE_GRAY_ALPHA )
png_set_gray_to_rgb( png );
if ( interlace != PNG_INTERLACE_NONE )
png_set_interlace_handling( png );
png_set_filler( png, 0xFF, PNG_FILLER_AFTER );
/* recheck header after setting EXPAND options */
png_read_update_info( png, info );
png_get_IHDR( png, info,
&imgWidth, &imgHeight,
&bitdepth, &color_type, &interlace,
NULL, NULL );
if ( bitdepth != 8 ||
!( color_type == PNG_COLOR_TYPE_RGB ||
color_type == PNG_COLOR_TYPE_RGB_ALPHA ) )
{
error = FT_THROW( Invalid_File_Format );
goto DestroyExit;
}
if ( metrics_only )
goto DestroyExit;
switch ( color_type )
{
default: /* Shouldn't happen, but ... */
case PNG_COLOR_TYPE_RGB_ALPHA:
png_set_read_user_transform_fn( png, premultiply_data );
break;
case PNG_COLOR_TYPE_RGB:
/* Humm, this smells. Carry on though. */
png_set_read_user_transform_fn( png, convert_bytes_to_data );
break;
}
if ( populate_map_and_metrics )
{
/* this doesn't overflow: 0x7FFF * 0x7FFF * 4 < 2^32 */
FT_ULong size = map->rows * (FT_ULong)map->pitch;
error = ft_glyphslot_alloc_bitmap( slot, size );
if ( error )
goto DestroyExit;
}
if ( FT_QNEW_ARRAY( rows, imgHeight ) )
{
error = FT_THROW( Out_Of_Memory );
goto DestroyExit;
}
for ( i = 0; i < (FT_Int)imgHeight; i++ )
rows[i] = map->buffer + ( y_offset + i ) * map->pitch + x_offset * 4;
png_read_image( png, rows );
png_read_end( png, info );
DestroyExit:
/* even if reading fails with longjmp, rows must be freed */
FT_FREE( rows );
png_destroy_read_struct( &png, &info, NULL );
FT_Stream_Close( &stream );
Exit:
return error;
}
#else /* !(TT_CONFIG_OPTION_EMBEDDED_BITMAPS && FT_CONFIG_OPTION_USE_PNG) */
/* ANSI C doesn't like empty source files */
typedef int pngshim_dummy_;
#endif /* !(TT_CONFIG_OPTION_EMBEDDED_BITMAPS && FT_CONFIG_OPTION_USE_PNG) */
/* END */