/***************************************************************************/
/* */
/* pngshim.c */
/* */
/* PNG Bitmap glyph support. */
/* */
/* Copyright 2013 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 <ft2build.h>
#include FT_INTERNAL_DEBUG_H
#include FT_INTERNAL_STREAM_H
#include FT_TRUETYPE_TAGS_H
#include FT_CONFIG_STANDARD_LIBRARY_H
#ifdef FT_CONFIG_OPTION_USE_PNG
/* We always include <stjmp.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 int
multiply_alpha( int alpha,
int color )
{
int temp = ( alpha * color ) + 0x80;
return ( temp + ( temp >> 8 ) ) >> 8;
}
/* Premultiplies data and converts RGBA bytes => native endian. */
static void
premultiply_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 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] = blue;
base[1] = green;
base[2] = red;
base[3] = 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] = blue;
base[1] = green;
base[2] = 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 = png_get_error_ptr( png );
FT_UNUSED( error_msg );
*error = FT_THROW( Out_Of_Memory );
#ifdef PNG_SETJMP_SUPPORTED
#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 = png_get_error_ptr( png );
*e = FT_THROW( Invalid_Stream_Read );
png_error( png, NULL );
return;
}
memcpy( data
, stream
->cursor
, length
);
FT_FRAME_EXIT();
}
static FT_Error
Load_SBit_Png( FT_Bitmap* map,
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_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;
png_byte* *rows;
if ( x_offset < 0 || x_offset + metrics->width > map->width ||
y_offset < 0 || 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 != FT_Err_Ok ||
(FT_Int)imgWidth != metrics->width ||
(FT_Int)imgHeight != metrics->height )
goto DestroyExit;
/* 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;
}
switch ( color_type )
{
default:
/* Shouldn't happen, but fall through. */
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 ( FT_NEW_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 );
FT_FREE( rows );
png_read_end( png, info );
DestroyExit:
png_destroy_read_struct( &png, &info, NULL );
FT_Stream_Close( &stream );
Exit:
return error;
}
#endif /* FT_CONFIG_OPTION_USE_PNG */
/* END */